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Alabama
Athens Shale and Lenoir Limestone undifferentiated (Ordovician)
Athens Shale and Lenoir Limestone undifferentiated - Athens Shale -- black graptolitic shale, locally contains interbedded dark-gray limestone. Lenoir Limestone -- dark-gray medium to thick-bedded argillaceous limestone; locally contains an interval of fenestral mudstone at the base (Mosheim Limestone Member).
Attalla Chert Conglomerate Member of the Chickamauga Limestone (Ordovician)
Attalla Chert Conglomerate Member of the Chickamauga Limestone - conglomerate of pebbles, cobbles, and boulders of chert and rare dolomite and quartzite in a sand-sized chert and quartz matrix; thin beds of gray-green or dusky-red shale common at base.
Attalla Chert Conglomerate Member of the Chickamauga Limestone (Ordovician)
Attalla Chert Conglomerate Member of the Chickamauga Limestone - conglomerate of pebbles, cobbles, and boulders of chert and rare dolomite and quartzite in a sand-sized chert and quartz matrix; thin beds of gray-green or dusky-red shale common at base.
Bangor and Monteagle Limestones undivided in part (Mississippian)
Bangor and Monteagle Limestones undivided in part - Bangor Limestone -- medium-gray bioclastic and oolitic limestone, containing interbeds of dusky-red and olive-green mudstone in upper part. Monteagle Limestone -- light-gray oolitic limestone containing interbedded argillaceous, bioclastic, or dolomitic limestone, dolomite, and medium-gray shale.
Bluff Springs Granite (Precambrian to Paleozoic)
Bluff Springs Granite - leucocratic quartz diorite (tonalite) to quartz monzonite or trondhjemite, locally foliated.
Chattanooga Shale (Devonian)
Chattanooga Shale - Brownish-black organic shale containing light to dark-gray sandstone and rare limestone interbeds near the base.
Chattanooga Shale (Devonian)
Chattanooga Shale - Brownish-black organic shale containing light to dark-gray sandstone and rare limestone interbeds near the base.
Chattanooga Shale (Devonian)
Chattanooga Shale - Brownish-black organic shale containing light to dark-gray sandstone and rare limestone interbeds near the base.
Chattanooga Shale and Frog Mountain Sandstone undifferentiated (Devonian)
Chattanooga Shale and Frog Mountain Sandstone undifferentiated (In areas mapped as Dcfm one or both units may be locally absent) - Chattanooga Shale -- Brownish-black organic shale containing light to dark-gray sandstone and rare limestone interbeds near the base. Frog Mountain Sandstone -- light to dark-gray sandstone with thin dark-gray shale interbeds, light-gray to black dolomudstone, glauconitic limestone, and fossiliferous chert locally in lower part.
Chepultepec and Copper Ridge Dolomites undifferentiated (Ordovician-Cambrian)
Chepultepec and Copper Ridge Dolomites undifferentiated - Light-gray to dark-bluish-gray thick-bedded dolomite and interbedded light-gray limestone; includes abundant chert.
Chepultepec and Copper Ridge Dolomites undifferentiated (Ordovician-Cambrian)
Chepultepec and Copper Ridge Dolomites undifferentiated - Light-gray to dark-bluish-gray thick-bedded dolomite and interbedded light-gray limestone; includes abundant chert.
Chepultepec and Copper Ridge Dolomites undifferentiated (Ordovician-Cambrian)
Chepultepec and Copper Ridge Dolomites undifferentiated - Light-gray to dark-bluish-gray thick-bedded dolomite and interbedded light-gray limestone; includes abundant chert.
Chickamauga Limestone (Ordovician)
Chickamauga Limestone - Medium to dark-gray thick to thin-bedded partly argillaceous, locally fossiliferous limestone. Restricted to the western part of the Valley and Ridge province and Murphrees Valley and Wills Valley anticlines. Locally includes a thin interval of Attalla Chert Conglomerate Member at base. Attalla Chert Conglomerate - conglomerate of pebbles, cobbles, and boulders of chert and rare dolomite and quartzite in a sand-sized matrix; thin beds of gray-green or dusky-red shale common at base.
Chickamauga Limestone (Ordovician)
Chickamauga Limestone - Medium to dark-gray thick to thin-bedded partly argillaceous, locally fossiliferous limestone. Restricted to the western part of the Valley and Ridge province and Murphrees Valley and Wills Valley anticlines. Locally includes a thin interval of Attalla Chert Conglomerate Member at base. Attalla Chert Conglomerate - conglomerate of pebbles, cobbles, and boulders of chert and rare dolomite and quartzite in a sand-sized matrix; thin beds of gray-green or dusky-red shale common at base.
Chilhowee Group undifferentiated (Cambrian)
Chilhowee Group undifferentiated - light to medium-gray arkose, arkosic conglomerate, and discontinous mudstone overlain by greenish-gray mudstone with minor siltstone and sandstone; dominantly light-gray pebbly quartzose sandstone in upper part.
Citronelle Formation (Pleistocene-Pliocene)
Citronelle Formation - moderate-reddish-brown deeply weathered fine to very coarse quartz sand and varicolored typically mottled lenticular beds of clay and clayey gravel. Limonite pebbles and lenses of limonite cemented sand occur locally in weathered exposures. Gravel is composed of chert and quartz pebbles.
Claiborne Group; Gosport Sand and Lisbon Formation undifferentiated in part (Eocene)
Lisbon Formation undifferentiated in part - (Claiborne Group), greenish-gray calcareous, glauconitic, fossiliferous clayey sand; marl; carbonaceous sand; carbonaceous silty clay; and coarse glauconitic, fossiliferous, quartz sand.
Claiborne Group; Tallahatta Formation (Eocene)
Tallahatta Formation - (Claiborne group), White to very light-greenish-gray thin-bedded to massive siliceous claystone; interbedded with thin layers of fossiliferous clay, sandy clay, and glauconitic sand and sandstone. White to light-greenish-gray fine to coarse sand and fine gravel occur at the base of the formation in southwest Alabama (Meridian Sand Member).
Claiborne/Jackson Group; Residuum (Eocene-Oligocene)
Residuum - (Claiborne/Jackson Group), White to moderate-reddish-orange locally mottled sandy clay and residual clay with scattered layers of gravelly medium to coarse sand, fossiliferous chert and limestone boulders and limonitic sand masses. Derived from solution and collapse of limestone in the Jackson Group and Oligocene Series and the slumping of Pliocene and Miocene sediments.
Cochran Formation (Cambrian)
Cochran Formation - poorly sorted arkosic sandstone and conglomerate containing interbedded greenish-gray siltstone and mudstone. The Cochran Formation is exposed only in northeastern Calhoun and northwestern Cleburne Counties.
Conasauga Formation (Cambrian)
Conasauga Formation - light to dark-gray finely to coarsely crystalline, medium to thick-bedded dolomite containing minor greenish-gray shale and light-bluish-gray chert. In the Columbiana area of Shelby County, the Conasauga is dominated by thin to medium-bedded, dark-gray dolomitic limestone and minor dark-gray shale. In Bibb County and southwestern Shelby County, the Conasauga consists of medium-bluish-gray fine-grained, thin-bedded argillaceous limestone and interbedded dark-gray shale. In the eastern Valley and Ridge the lower part includes dark-green to pale-olive fossiliferous shale with a few dark-gray limestone interbeds.
Dadeville Complex; Agricola Schist (Precambrian to Paleozoic)
Agricola Schist - biotiite +/- garnet +/- sillimanite-feldspar-quartz schist, interlayered with thin-bedded dark-brown hornblende amphibolite; contains pegmatite pods and veins.
Dadeville Complex; Mafic and ultramafic rock (Precambrian to Paleozoic)
Mafic and ultramafic rock - ultramafic rock including enstatite pyroxenite, layered actinolite-tremolite amphibolite altered locally to serpentine, anthophyllite, and talc; metanorite; metagabbro; hornblendite; garnet-hornblendite, and massive amphibolite.
Dadeville Complex; Ropes Creek Amphibolite (Precambrian to Paleozoic)
Ropes Creek Amphibolite - layered and massive amphibolite; locally includes hornblende migmatite and ultramafic pods.
Dadeville Complex; Waresville Schist (Precambrian to Paleozoic)
Waresville Schist - banded amphibolite interlayered with chlorite schist, chlorite amphibolite, chlorite-actinolite schist, chlorite +/- magnetite quartzite, and actinolite quartzite; may include small ultramafic pods.
Dadeville Complex; Waverly Gneiss (Precambrian to Paleozoic)
Waverly Gneiss - feldspathic biotite-hornblende gneiss with thin layers of amphibolite, calc-silicate rock, garnet quartzite, and muscovite schist; locally rich in manganese.
Emuckfaw Group; Emuckfaw Group undifferentiated in part (Precambrian to Paleozoic)
Emuckfaw Group undifferentiated in part - interbedded muscovite +/- garnet-biotite schist, metagraywacke, calc-silicate rock, and quartzite; rare thin amphibolite. Includes thin layers of aluminous graphitic schist. Locally sheared to mylonite schist.
Eutaw Formation (Cretaceous)
Eutaw Formation - Light-greenish-gray to yellowish-gray cross-bedded, well-sorted, micaceous, fine to medium quartz sand that is fossiliferous and glauconitic in part and contains beds of greenish-gray micaceous, silty clay and medium-dark-gray carbonaceous clay. Light-gray glauconitic fossiliferous sand, thin beds of sandstone, and massive accumulations of fossil oyster shells occur locally in the upper part of the formation in western AL (Tombigbee Sand Member). In eastern AL thin to thick-bedded accumulations of the fossil oyster Ostrea cretacea Morton occur throughout much of the formation.
Floyd Shale (Mississippian)
Floyd Shale - Dark-gray shale, sideritic in part; thin beds of sandstone, limestone and chert are locally present; beds of partly bioclastic, partly argillaceous limestone are abundant in parts of Calhoun and Cherokee Counties.
Fort Payne Chert (Mississippian)
Fort Payne Chert - Very light to light-olive-gray, thin to thick-bedded fine to coarse-grained bioclastic (abundant pelmatozoans) limestone containing abundant nodules, lenses and beds of light to dark-grey chert. Upper part of formation locally consists of light-bluish-gray laminated siltstone containing vugs lined or filled with quartz and scattered throughout the formation are interbeds of medium to greenish-gray shale, shaly limestone and siltstone. Commonly present below the Fort Payne is a light-olive-gray claystone or shale (Maury Formation) which is mapped with the Fort Payne. The apparent thickness of the Fort Payne in this province varies due to differnetial dissolution of carbonate in the formation.
Fort Payne Chert (Mississippian)
Fort Payne Chert - Very light to light-olive-gray, thin to thick-bedded fine to coarse-grained bioclastic (abundant pelmatozoans) limestone containing abundant nodules, lenses and beds of light to dark-grey chert. Upper part of formation locally consists of light-bluish-gray laminated siltstone containing vugs lined or filled with quartz and scattered throughout the formation are interbeds of medium to greenish-gray shale, shaly limestone and siltstone. Commonly present below the Fort Payne is a light-olive-gray claystone or shale (Maury Formation) which is mapped with the Fort Payne.
Frog Mountain Sandstone (Devonian)
Frog Mountain Sandstone -- light to dark-gray sandstone with thin dark-gray shale interbeds, light-gray to black dolomudstone, glauconitic limestone, and fossiliferous chert locally in lower part.
Greensport Formation (Ordovician)
Greensport Formation - variegated dusky-red and dark-yellowish-orange shale, calcareous mudstone, limestone, siltstone, and minor sandstone.
Hatchet Creek Group; Hanover Schist (Precambrian to Paleozoic)
Hanover Schist - coarse to fine-grained feldspathic biotite-sericite-quartz-muscovite schist, commonly containing staurolite, garnet, and locally sillimanite in northeastern outcrop areas includes zones of aluminous graphite schist, hornblende quartzite, garnet quartzite, and rare amphibolite. Schist commonly retrograded to sericite-garnet-quartz schist. Numerous granitic pegmatites.
Heflin Phyllite (Cambrian?)
Heflin Phyllite - grayish-green, medium-gray, and medium-bluish-gray calcareous sandy metasiltstone interbedded with minor greenish-gray fine to coarse-grained metasandstone and rare thin lenses of calcite and dolomite marble; an interval of greenish-gray to dark-gray phyllitic quartzite or quartz-pebble metaconglomerate is locally present near the base. The Heflin underlies the Lay Dam Formation and overlies the rocks tentatively identified as the Chilhowee Group undifferentiated.
Higgins Ferry Group (Precambrian to Paleozoic)
Higgins Ferry Group - thinly layered coarse to fine-grained biotite-feldspar-quartz gneiss, sericite-feldspar-muscovite schist, +/- biotite +/- garnet-muscovite schist, and biotite-garnet feldspathic gneiss; locally common pegmatites.
Jackson Group undifferentiated (Eocene)
Jackson Group undifferentiated - The units of the Jackson Group are the Yazoo Clay and Crystal River and Moodys Branch Formations. Descriptions of the members of the Yazoo Clay follow in decending order. Shubuta Member - in western Alabama consists of light-greenish-gray to white plastic fossiliferous, calcareous clay containing irregular calcareous nodules. From the Tombigbee River eastward the Shubuta becomes more calcareous and grades into massive clayey glauconitic limestone. Eastward from the Alabama River , equivalent beds grade into the Crystal River Formation. Pachuta Marl Member - light-greenish-grey glauconitic, fossiliferous clayey sand and sandy limestone traceable from western Alabama eastward to Covington County where it grades into the Crystal River Formation. Cocoa Sand Member - yellowish-gray firm calcareous, fossiliferous fine to medium sand or sandy limestone or greenish-grey micaceous, calcareous, very clayey sand. Calcareous and clayey sand equivalent to the Cocoa is traceable from western Alabama to the Conecuh River area. North Twistwood Creek Clay Member - greenish-gray plastic calcareous, sparsely fossiliferous, blocky massive clay; grades into Crystal River formation in southeast AL. Crystal River Formation - white to yellowish-grey medium-grained to coquinoid limestone that is soft and chalky to compact and brittle; principally in southeastern AL but interfingers westward with members of the Yazoo Clay. Moodys Branch Formation - greenish-gray to pale-yellowish-orange glauconitic, calcareous, fossiliferous sand and sandy limestone; underlies the Yazoo Clay and the Crystal River Formation.
Jacksons Gap Group; Jacksons Gap Group undifferentiated in part (Precambrian to Paleozoic)
Jacksons Gap Group undivided - principally graphitic sericite (muscovite)-quartz schist; includes sericite-quartz phyllonite; sericite phyllonite, blastomylonite, porphyroclastic blastomylonite schist, and mylonite quartzite occur principally along margins in south and form most of unit northeast of Jacksons Gap, Tallapoosa County.
Jacksons Gap Group; Tallassee Metaquartzite (Precambrian to Paleozoic)
Jacksons Gap Group; Tallassee Metaquartzite - medium to fine-grained, massive to thin-bedded quartzite and metaconglomerate and thin beds of graphitic quartz schist, locally contains small garnets.
Kahatchee Mountain Group; Brewer Phyllite (Precambrian?-Cambrian?)
Brewer Phyllite - dusky-red micaceous slate and phyllite, locally containing interbedded micaceous arkosic quartzite and metasiltstone; locally at the base is interbedded calcite and dolomite marble.
Kahatchee Mountain Group; Sawyer Limestone Member of Brewer Phyllite (Precambrian?-Cambrian?)
Sawyer Limestone Member of Brewer Phyllite - light to medium-gray argillaceous, silty to siliceous calcite and dolomite marble interbedded with phyllite and quartzite, locally cherty.
Kahatchee Mountain Group; Waxahatchee Slate (Precambrian?-Cambrian?)
Waxahatchee Slate - dark-gray to grayish-green thin-bedded, micaceous metasiltstone, slate, and fine-grained quartzite.
Knox Group undifferentiated (Ordovician-Cambrian)
Knox Group undifferentiated - Light-gray to light-brown locally sandy dolomite, dolomitic limestone, and limestone; characterized by abundant light-colored chert.
Knox Group undifferentiated in part (Ordovician-Cambrian)
Knox Group undifferentiated in part - light-gray to light-brown locally sandy dolomite, dolomitic limestone, and limestone; characterized by abundant light-colored chert.
Little Oak and Lenoir Limestones undifferentiated (Ordovician)
Little Oak and Lenoir Limestones undifferentiated - dark-gray argillaceous, fossiliferous medium to thick-bedded limestone; locally contains rare chert in upper part and an interval of fenestral mudstone in lower part (Mosheim Limestone Member of the Lenoir Limestone). Between Siluria and Pelham in Shelby County, the Little Oak and Lenoir Limestones are separated by a tongue of the Athens Shale.
Little Oak and Newala Limestones undifferentiated (Ordovician)
Little Oak and Newala Limestones undifferentiated - Little Oak Limestone -- dark-gray medium to thick-bedded fossiliferous, argillaceous to silty limestone containing chert nodules. Locally includes thin beds of bentonite in the upper part. Newala Limestone -- light to dark-gray thick-bedded micritic and peloidal limestone and minor dolomite.
Little Oak Limestone (Ordovician)
Little Oak Limestone - dark-gray medium to thick-bedded fossiliferous, argillaceous to silty limestone containing chert nodules. Locally includes thin beds of bentonite in the upper part.
Mad Indian Group (Precambrian to Paleozoic)
Mad Indian Group - fine-grained feldspathic biotite gneiss; medium to coarse-grained muscovite-biotite-garnet schist; locally kyanite and sillimanite. Many of the schists have been retrograded to chlorite-garnet-quartz-sericite schist. Both mi and migr extensively cut by feldspathic dikes and pegmatites.
Metaclastic rocks of unknown affinity (Precambrian to Paleozoic)
Metaclastic rocks of unknown affinity - in the area south of Talladega, Talladega County, the unit includes greenish-gray chlorite-sericite phyllite; in small area south of Childersburg the unit consists of greenish-gray chlorite-sericite phyllite and slate locally containing interbeds of metagraywacke; and in the area east of Columbiana, Shelby County, the unit includes dark-greenish-gray slate and metasiltstone containing interbedded coarse-grained to conglomerate quartzite.
Midway Group; Clayton Formation (Paleocene)
Clayton Formation - (Midway Group), White to yellowsih-gray argillaceous limestone occurs in the upper part (McBryde Limestone Member): the lower part is medium-gray fossiliferous calcareous silt, glauconitic sand and thin beds of sandy limestone and calcareous sandstone (Pine Barren Member). At the base of the formation in southeast AL is a gravelly medium to coarse sand containing clay pebbles. The formation thins west of Wilcox County and westward from Thomaston in eastern Marengo County is mapped with the Porters Creek Formation. The formation is generally deeply weathered and fresh exposures are rare. In western areas exposures consist of weathered white to yellowish-gray argillaceous, fossiliferous sandy limestone, ferruginous sand, and fossiliferous sandstone. In eastern areas exposures consist of residual accumulations of chert boulders, moderate-reddish-orange sand, and clay containing masses and thin layers of iron minerals (limonite-goethite).
Midway Group; Naheola Formation (Paleocene)
Naheola Formation - (Midway Group), The Naheola Formation is restricted to western AL and pinches out in western Butler County. Descriptions of the members of the formation follow in descending order. Coal Bluff Marl Member - glauconitic sand, thin-bedded silty clay, and sandy fossiliferous marl; Oak Hill Member - laminated silt, clay, and fine sand; contains a prominent bed of lignite near the top. The Coal Bluff Marl Member in Sumter County and in parts of Marengo County is mostly cross-bedded fine to coarse sand that is indistinguishable from the overlying lower beds of the Nanafalia Formation. Therefore, in these areas, the contact between the two is mapped at the top of the Oak Hill Member of the Naheola.
Midway Group; Porters Creek Formation (Paleocene)
Porters Creek Formation - (Midway Group), dark-gray massive plastic clay in western AL with a thin bed of glauconitic shell marl at the top (Mathews Landing Marl Member). Becomes calcareous eastward grading into light-greenish-gray calcareous, micaceous, clayey fine to medium sand, medium-gray sandy, calcareous clay and white to light-gray thin bedded partly clayey, fossiliferous limestone. East of Crenshaw County, owing to lithologic similarity, beds correlative with the Porters Creek are included in the Clayton Formation.
Miocene Series undifferentiated (Miocene)
Miocene Series undifferentiated - Moderate-yellowish-orange thin-bedded to massive fine to coarse sand, gravelly sand, thin-bedded to massive clay and sandy clay. Clays are plastic in part. Limonite pellets occur in places along clay-sand contacts. Gravel is composed of quartz and chert granules and pebbles. Locally the upper part of the unit is Pliocene in age.
Moffits Mill Schist (Precambrian to Paleozoic)
Moffits Mill Schist - interlayered biotite-epidote-muscovite-quartz schist, metagraywacke, and quartzite.
Monteagle Limestone (Mississippian)
Monteagle Limestone - Light-gray oolitic limestone containing interbedded argillaceous, bioclastic, or dolomitic limestone, dolomite, and medium-gray shale.
Monteagle Limestone (Mississippian)
Monteagle Limestone - Light-gray oolitic limestone containing interbedded argillaceous, bioclastic, or dolomitic limestone, dolomite, and medium-gray shale.
Monteagle Limestone (Mississippian)
Monteagle Limestone - Light-gray oolitic limestone containing interbedded argillaceous, bioclastic, or dolomitic limestone, dolomite, and medium-gray shale.
Mylonitic and Cataclastic Rocks in the Brevard, Towaliga, and Goat Rock Fault Zones (Precambrian to Paleozoic)
Mylonitic and Cataclastic Rocks in the Brevard, Towaliga, and Goat Rock Fault Zones - mylonite and blastomylonite; contains minor ultramylonite, mylonite schist, and mylonite gneiss.
Mylonitic and Cataclastic Rocks in the Brevard, Towaliga, and Goat Rock Fault Zones (Precambrian to Paleozoic)
Mylonitic and Cataclastic Rocks in the Brevard, Towaliga, and Goat Rock Fault Zones - blastomylonite, mylonite gneiss, locally includes mylonite schist and mylonite quartzite in Towaliga fault zone.
Nashville and Stones River Groups undifferentiated (Ordovician)
Nashville and Stones River Groups undifferentiated - medium to dark-gray fossiliferous limestone, argillaceous in part; yellowish-gray laminated silty limestone in upper part. Contains one or more thin beds of bentonite and bentonitic shale.
Newala and Longview Limestones undifferentiated (Ordovician)
Newala and Longview Limestones undifferentiated - light to dark-grey thick-bedded limestone and dolomite, cherty in part.
Nichols Formation (Cambrian)
Nichols Formation - massive to laminated greenish-gray and black micaceous mudstone containing minor interbeds of siltstone and very fine-grained sandstone.
Oligocene Series undifferentiated (Oligocene)
Oligocene Series undifferentiated - Descriptions of the units of the Oligocene Series follow in descending order. Paynes Hammock Sand - locally fossiliferous, calcareous, argillaceous medium to coarse sand; pale-blue-green clay; and thin-bedded sandy limestone; exposed at Paynes Hammock and at St. Stephens. Chickasawhay Limestone - white to yellowish-gray fossiliferous, glauconitic limestone and soft marl. Byram Formation includes three members in descending order: Bucatunna Clay Member - dark, bentonitic, carbonaceous, sparsely fossiliferous clay and greyish-yellow sand; unnamed marl member - light-grey to yellowish-grey sandy, glauconitic , fossiliferous marl; Glendon Limestone Member - irregularly indurated coquinoid and crystalline limestone, weathering to indurated rock containing large tubular cavities, locally known as 'horsebone'. Marianna Limestone - white to yellowish-grey soft, porous, very fossiliferous limestone. Forest Hill sand - dark-greenish-grey carbonaceous clay with lenses of glauconitic fossiliferous sand; extends eastward from MS into Choctaw, Clarke and Washington Counties. Red Bluff Clay - greenish-gray calcareous clay locally containing selenite crystals, yellowish-grey glauconitic, fossiliferous limestone; and light-gray silty clay with interbeds of sand (Forest Hill equivalent); from Tombigbee River eastward grades into glauconitic fossiliferous limestone equivalent to the Bumpnose Limestone. Bumpnose Limestone - very light-gray to yellowish-gray chalky, subcoquinoid, glauconitic, argillaceous, fossiliferous limestone; intertongues with Red Bluff Clay in vicinity of the Alabama River and is readily differentiated eastward from the Sepulga River.
Opelika Complex; Auburn Gneiss (Precambrian to Paleozoic)
Auburn Gneiss - fine-grained biotite-oligoclase gneiss intermixed with coarse-grained muscovite-biotite schist; locally contains muscovite-rich pegmatite.
Paleozoic shale undifferentiated (Mississippian)
Paleozoic shale undifferentiated - Dark-gray shale and mudstone, locally containing thin interbeds and lenses of dark-greenish-gray sandstone includes Athens Shale and probable Floyd Shale in the structural windows near Anniston, Calhoun County.
Paleozoic shale undifferentiated (Mississippian)
Paleozoic shale undifferentiated - Dark-gray shale and mudstone, locally containing thin interbeds and lenses of dark-greenish-gray sandstone includes probable Floyd Shale in area east of Gadsden, Etowah County.
Parkwood and Pennington Formations (Pennsylvanian-Mississippian)
Parkwood and Pennington Formations undifferentiated - Interbedded medium to dark-gray shale and light to medium-gray sandstone, locally contains lithic conglomerate, dusky-red and grayish-green mudstone, argillaceous limestone, and clayey coal.
Parkwood and Pennington Formations undifferentiated (Pennsylvanian-Mississippian)
Parkwood and Pennington Formations undifferentiated - Interbedded medium to dark-gray shale and light to medium-gray sandstone, locally contains lithic conglomerate, dusky-red and grayish-green mudstone, argillaceous limestone, and clayey coal.
Parkwood Formation (Pennsylvanian-Mississippian)
Parkwood Formation - Interbedded medium to dark-gray shale and light to medium-gray sandstone; locally contains dusky-red and grayish-green mudstone, argillaceous limestone, and clayey coal.
Parkwood Formation (Pennsylvanian-Mississippian)
Parkwood Formation - Interbedded medium to dark-gray shale and light to medium-gray sandstone; locally contains dusky-red and grayish-green mudstone, argillaceous limestone, and clayey coal.
Parkwood Formation and Floyd Shale undifferentiated (Pennsylvanian-Mississippian)
Parkwood Formation and Floyd Shale undifferentiated - Parkwood Formation -- Interbedded medium to dark-gray shale and light to medium-gray sandstone; locally contains dusky-red and grayish-green mudstone, argillaceous limestone, and clayey coal. Floyd Shale -- Dark-gray shale, sideritic in part; thin beds of sandstone, limestone and chert are locally present; beds of partly bioclastic, partly argillaceous limestone are abundant in parts of Calhoun and Cherokee Counties.
Pennington Formation (Mississippian)
Pennington Formation - Medium-gray shale, containing interbedded limestone, dolomite, argillaceous sandstone, dusky-red and grayish-olive mudstone, and minor shaly coal. Mainly restricted to eastern part of Interior Low Plateaus province and where less than 100 feet thick the formation is included in the Bangor Limestone.
Pennington Formation (Mississippian)
Pennington Formation - Medium-gray shale, containing interbedded limestone, dolomite, argillaceous sandstone, dusky-red and grayish-olive mudstone, and minor shaly coal. Mainly restricted to northeastern AL and part of the Sequatchie anticline. Where less than 100 feet thick the formation is included in the Bangor Limestone.
Poe Bridge Mountain Group (Precambrian to Paleozoic)
Poe Bridge Mountain Group - coarse to fine-grained feldspathic graphite schist, +/- staurolite +/- kyanite +/- sillimanite-muscovite-biotite schist, and garnet-biotite-muscovite schist, and gneiss; locally common pegmatites. Rocks in the area of Turkey Heaven Mountain in Cleburne and Randolph Counties that are here assigned to the Poe Bridge Mountain Group also have been interpreted as part of the Wedowee Group.
Pottsville Formation (Pennsylvanian)
Pottsville Formation - Light-gray thin to thick-bedded quartzose sandstone and conglomerate containing interbedded dark-gray shale, siltstone, and coal. Mapped on Lookout Mountain, Blount and Chandler Mountains, and Sand Mountain northeats of Blount County, and on the mountains of Jackson, Marshall and Madison Counties north and west of the TN river.
Pottsville Formation (lower part) (Pennsylvanian)
Pottsville Formation (lower part) - Light-gray thick-bedded to massive pebbly quartzose sandstone, containing varying amounts of interbedded dark-gray shale, siltstone, and thin discontinuos coal. The Boyles Sandstone Member is a formally named unit in the lower part of the formation. Top of unit is mapped at the Black Creek coal.
Pottsville Formation (lower part) (Pennsylvanian)
Pottsville Formation (lower part) - Light-gray thick-bedded to massive pebbly quartzose sandstone, containing varying amounts of interbedded dark-gray shale, siltstone, and thin discontinuos coal. In both the Cahaba and Coosa synclinoria the members in descending order include: the Pine Sandstone Member and the Shades Sandstone Member. Top of unit is mapped at top of Pine Sandstone Member.
Pottsville Formation (upper part) (Pennsylvanian)
Pottsville Formation (upper part) - Interbedded dark-gray shale, siltstone, medium-gray sandstone, and coal in cyclic sequences. In descending order the members include: Razburg Sandstone Member, Camp Branch Sandstone Member, Lick Creek Sandstone Member, and the Bremen Sandstone Member.
Pottsville Formation (upper part) (Pennsylvanian)
Pottsville Formation (upper part) - Interbedded dark-gray shale, siltstone, medium-gray sandstone, and coal in cyclic sequences. The members present in the Cahaba synclinorium in descending order include: the Straven Conglomerate Member, Rocky Ridge Sandstone Member, and Chestnut Sandstone Member. The members present in the Coosa synclinorium in descending order include: Straight Ridge Sandstone Member and Wolf Ridge Sandstone Member.
Pride Mountain Formation (Mississippian)
Pride Mountain Formation - Medium to dark-gray shale, containing one to three units of a variable combination of sandstone and limestone in the lower part; locally contains rare interbeds of dusky-red and greenish-gray mudstone.
Pride Mountain Formation (Mississippian)
Pride Mountain Formation - Medium to dark-gray shale, containing one to three units of a variable combination of sandstone and limestone in the lower part; locally contains rare interbeds of dusky-red and greenish-gray mudstone.
Pride Mountain Formation (Mississippian)
Pride Mountain Formation - Medium to dark-gray shale, containing one to three units of a variable combination of sandstone and limestone in the lower part; locally contains rare interbeds of dusky-red and greenish-gray mudstone.
Red Mountain Formation (Silurian)
Red Mountain Formation - Interbedded yellowish-gray to moderate-red sandstone, siltstone and shale; greenish-gray to moderate-red fossiliferous partly silty and sandy limestone; few thin hematitic beds.
Red Mountain Formation (Silurian)
Red Mountain Formation - dark-reddish-brown to olive-gray partly fossiliferous, mostly fine-grained sandstone interbedded with siltstone and shale; minor amounts of bioclastic limestone and conglomerate sandstone; includes hematitic beds and beds of ferruginous sandstone, outcrops in northeastern AL are finer grained and include more limestone.
Red Mountain Formation (Silurian)
Red Mountain Formation - Interbedded yellowish-gray to moderate-red sandstone, siltstone and shale; greenish-gray to moderate-red fossiliferous partly silty and sandy limestone; few thin hematitic beds.
Rockford Granite (Precambrian to Paleozoic)
Rockford Granite - leucocratic granite, granodiorite, and trondhjemite; locally well foliated, numerous pegmatites. Includes unnamed granitoids in Chilton County.
Rome Formation (Cambrian)
Rome Formation - variegated thinly interbedded mudstone, shale, siltstone, and sandstone; limestone and dolomite occur locally. Quartzose sandstone commonly present near top of formation.
Selma Group; Blufftown Formation (Cretaceous)
Blufftown Formation - (Selma Group), The Blufftown extends from the Chattahoochee River Valley westward into central Russell County where it is divided into two westward-extending tongues by an eastward-extending tongue of the Mooreville Chalk. In the Chattahoochee River Valley the Blufftown is mainly glauconitic calcareous fine sand, micaceous clay and marl, fossiliferous clay, gray calcareous fossiliferous sandstone, and carbonaceous clay and silt. To the west the lower tongue of the Blufftown is gravelly sand, glauconitic sand, calcareous clay, and sandy clay and merges with the lower part of the Mooreville Chalk in southwestern Macon County. The upper tongue is mainly calcareous sandy clay and micaceous silty fine sand with thin layers of limestone and sandstone. The upper tongue merges with the Mooreville Chalk and the lower part of the Demopolis Chalk in western Bullock County.
Selma Group; Demopolis Chalk (Cretaceous)
Demopolis Chalk - (Selma Group), Light-gray to medium-light-gray compact, brittle chalk overlain by abundantly fossiliferous chalky marl, very clayey chalk, and calcareous clay (Bluffport Marl Member). In south-central Montgomery County the Demopolis is split into two eastward extending tongues by a westward-extending tongue of the Cusseta Sand Member of the Ripley Formation. The lower tongue is pale-olive to yellowish-gray silty to finely sand, micaceous, fossiliferous chalk that eastward becomes more sandy and merges with the Cusseta in central Bullock County. The upper tongue is yellowish-gray clayey, very finely sandy, micaceous chalk that merges with the Ripley in southeastern Montgomery County.
Selma Group; Mooreville Chalk (Cretaceous)
Mooreville Chalk - (Selma Group), Yellowish-gray to olive-gray compact fossiliferous clayey chalk and chalky marl. The unconformable contact at the base is characterized by a bed of glauconitic, chalky sand containing phosphate pellets and molds of fossils. The Arcola Limestone Member at the top consists of two to four beds of light-gray brittle, dense, fossiliferous limestone separated by beds of light-gray to pale-olive calcareous clay.
Selma Group; Prairie Bluff Chalk (Upper Cretaceous)
Prairie Bluff Chalk - (Selma Group), Very light-gray to light-bluish-gray firm sandy, fossiliferous brittle chalk and grayish-black silty sandy calcareous glauconitic, fossiliferous clay; semi-indurated beds of sandy, clayey limestone are present in some exposures. Abscent locally in parts of Marengo, Dallas and Wilcox Counties where overlapped by the Clayton Formation or eroded. The Prairie Bluff thins eastward from southwestern Lowndes County to northern Pike County where it interfingers with the Providence Sand.
Selma Group; Providence Sand (Cretaceous)
Providence Sand - (Selma Group), Upper part consists of cross-bedded fine to coarse sand and white, dark-gray and pale-red-purple mottled clay containing lignite, sand, and kaolin; lower part consists of dark-gray laminated to thin-bedded silty clay and abundantly micaceous, carbonaceous, fossiliferous very fine to fine sand. The Providence Sand extends eastward from southeastern Lowndes County into Georgia.
Selma Group; Ripley Formation (Cretaceous)
Ripley Formation - (Selma Group), Light-gray to pale-olive massive, micaceous, glauconitic, fossiliferous fine sand; sandy calcareous clay; and thin indurated beds of fossiliferous sandstone.
Sequatchie Formation (Ordovician)
Sequatchie Formation - dusky-red to light-olive-gray siltstone, sandstone, shale, and dolomite, regular but uneven bedding.
Sequatchie Formation (Ordovician)
Sequatchie Formation - Grayish-red, grayish-green, and yellowish-gray thin-bedded calcareous shale and calcareous mudstone containing interbedded fossiliferous limestone, and medium-gray to moderate-red partly sandy and glauconitic, medium to coarse-grained bioclastic limestone.
Sequatchie Formation (Ordovician)
Sequatchie Formation - Grayish-red, grayish-green, and yellowish-gray thin-bedded calcareous shale and calcareous mudstone containing interbedded fossiliferous limestone, and medium-gray to moderate-red partly sandy and glauconitic, medium to coarse-grained bioclastic limestone. In Jackson County, includes the Leipers Limestone and Inman Formation.
Sequatchie Formation, Colvin Mountain Sandstone, Greensport Formation undifferentiated (Ordovician)
Sequatchie Formation, Colvin Mountain Sandstone, Greensport Formation undifferentiated - variegated dusky-red and pale-yellowish-orange shale, calcareous mudstone, dolomite, siltstone, and minor sandstone. Mapped in areas of facies transition with the Chickamauga Limestone (Canoe Creek, Dunaway, and Hensley Mountains).
Sequatchie Formation, Colvin Mountain Sandstone, Greensport Formation undifferentiated (Ordovician)
Sequatchie Formation, Colvin Mountain Sandstone, Greensport Formation undifferentiated - variegated dusky-red and pale-yellowish-orange shale, calcareous mudstone, dolomite, siltstone, and minor sandstone. Mapped in areas of facies transition with the Chickamauga Limestone (Scraper Mountain) and in the structurally complex area at the east end of Dry Creek Mountain.
Silurian System undivided (Includes Wayne Group and Brassfield Limestone) (Silurian)
Silurian System undivided (Includes Wayne Group and Brassfield Limestone) - Wayne Group - medium-gray, greenish-gray, and moderate-red argillaceous limestone; moderate-red and greenish-gray shale; and grayish-green fossiliferous limestone with scattered pink calcite crystals. Brassfield Limestone - greenish-gray to light-brownish-gray argillaceous, dolomitic, cherty, sandy, glauconitic limestone.
Stones River Groups undifferentiated in part (Ordovician)
Stones River Groups undifferentiated in part - medium to dark-gray thick to thin-bedded limestone, argillaceous in part, locally very fossiliferous. Contains a zone of bentonite and bentonitic shale near the top. Mapped seperately from the Nashville Group only in Jackson County.
Sylacauga Marble Group; Fayetteville Phyllite (Cambrian?-Ordovician?)
Fayetteville Phyllite - dusky-red and medium-gray phyllite and slate interlayered with light-brown to light-gray feldspathic metasiltstone, fine-grained metasandstone and dolomite marble.
Sylacauga Marble Group; Jumbo Dolomite (Cambrian?-Ordovician?)
Jumbo Dolomite - light to medium-gray thin to thick-bedded dolomite marble; contains intraclast-bearing dolomite, locally sandy in middle part.
Talladega Group; Jemison Chert and Chulafinnee Schist undifferentiated (Silurian?-Devonian)
Jemison Chert and Chulafinnee Schist undifferentiated - grayish-white to yellowish-orange massive, thick-bedded, fine-grained, locally argillaceous, locally fossiliferous metachert and light to dark-greenish-gray fine to medium-grained fissile quartz-sericite-chlorite phyllite and schist which locally includes thin chlorite phyllite and quartzose phyllite beds.
Talladega Group; Lay Dam Formation (Silurian?-Devonian)
Lay Dam Formation (Talladega Group) - interbedded dark-green phyllite, medium-gray to light-brown and black metasiltstone, dark-green feldspathic metagraywacke, and light-gray and dark-gray medium to coarse-grained arkosic quartzite and metaconglomerate; graphitic phyllite common in upper part. In Cleburne and Calhoun Counties, rocks mapped as the Lay Dam include the Abel Gap Formation of Bearce (1973) and consist of interbedded greenish-gray metasiltstone and quartzite, black phyllitic metasiltstone, medium-gray to greenish-gray arkosic quartzite, and dark-gray pyritic quartzite. In Clay Chounty the upper part of the Lay Dam includes black graphitic sericite phyllite and slate reportedly containing plant fossils (Erin Slate Member).
Talladega Group; Lay Dam Formation, unnamed diamictite facies (Silurian?-Devonian)
Talladega Group; Lay Dam Formation, unnamed diamictite facies - Unnamed diamictite facies of Lay Day Formation in Coosa and Chilton Counties consists of cobbles and boulders of carbonate, pelitic rocks, quartzite, chert, felsic plutonic rocks, and gneiss in a metagraywacke matrix.
Tuscaloosa Group; Coker Formation (Cretaceous)
Coker Formation - (Tuscaloosa Group), Light-colored micaceous very fine to medium sand, cross-bedded sand, varicolored micaceous clay, and a few thin gravel beds containing quartz and chert pebbles. Beds of thinly laminated finely glauconitic very fine to fine sand, silt and dark-gray carbonaceous clay (Eoline Member) occur locally in the lower part in western AL. Locally quartz and chert gravels at the base of the formation range in size from very fine pebbles to large cobbles. In southeastern Elmore County the formation includes marine sediments consisting of glauconitic, fossiliferous, quartzose fine to medium sand and medium-gray carbonaceous silty clay. Not mapped east of the Tallapoosa River.
Tuscaloosa Group; Gordo Formation (Cretaceous)
Gordo Formation - (Tuscaloosa Group), Massive beds of cross-bedded sand, gravelly sand, and lenticular beds of locally carbonaceous partly mottled moderate-red and pale-red-purple clay; lower part is predominantly a gravelly sand consisting chiefly of chert and quartz pebbles. Not mapped east of the Tallapooza River.
Tuscaloosa Group undifferentiated (Cretaceous)
Tuscaloosa Group undifferentiated - Light-gray to moderate-reddish-orange clayey, gravelly fine to very coarse sand; massive mottled sandy clay; local wood and leaf beds; and thin beds of indurated sandstone. Gravel consists mainly of quartz and quartzite and range in size from very fine pebbles to large cobbles. Mapped eats of the Tallapoosa River.
Tuscumbia Limestone and Fort Payne Chert undifferentiated (Mississippian)
Tuscumbia Limestone and Fort Payne Chert undifferentiated - Tuscumbia Limestone -- light to dark-gray fossiliferous and oolitic partly argillaceous and cherty limestone, absent locally and too thin to map seperately. Fort Payne Chert -- dark-gray to light-gray limestone with abundant irregular light-gray chert nodules and beds. Commonly present below the Fort Payne is greenish-gray to grayish-red phosphatic shale (Maury Formation) which is mapped with the Tuscumbia Limestone and Fort Payne Chert undifferentiated.
Tuscumbia Limestone and Fort Payne Chert undifferentiated (Mississippian)
Tuscumbia Limestone and Fort Payne Chert undifferentiated - Tuscumbia Limestone -- light to dark-gray fossiliferous and oolitic partly argillaceous and cherty limestone. Apparently present only along part of the northwest limb of the Coosa synclinorium. Fort Payne Chert -- dark-gray to light-gray limestone with abundant irregular light-gray chert nodules and beds. Commonly present below the Fort Payne is greenish-gray to grayish-red phosphatic shale (Maury Formation) which is mapped with the Tuscumbia Limestone and Fort Payne Chert undifferentiated.
Tuscumbia Limestone and Fort Payne Chert undivided (Mississippian)
Tuscumbia Limestone and Fort Payne Chert undivided - Tuscumbia Limestone -- light-gray partly oolitic limestone; very coarse bioclastic crinoidal limestone common; light-gray chert nodules and concretions locally abundant. Fort Payne Chert -- very light to light-olive-gray, thin to thick-bedded fine to coarse-grained bioclastic (abundant pelmatozoans) limestone containing abundant nodules, lenses and beds of light to dark-grey chert. Upper part of formation locally consists of light-bluish-gray laminated siltstone containing vugs lined or filled with quartz and scattered throughout the formation are interbeds of medium to greenish-gray shale, shaly limestone and siltstone. Lenses of dark-gray siliceous shale occur locally at the base of the Fort Payne in Wills Valley. Commonly present below the Fort Payne is a ligh-olive-gray claystone or shale (Maury Formation) which is mapped with the Fort Payne. The Tuscumbia and Fort Payne are undifferentiated in Murphrees and Wills Valleys.
Uchee Complex; Phenix City Gneiss (Precambrian to Paleozoic)
Phenix City Gneiss - biotite-epidote quartz diorite gneiss and biotite-hornblende gneiss; locally includes migmatitic amphibolite; cut by numerous granitic veins.
Wacoochee Complex; Halawaka Schist (Precambrian to Paleozoic)
Halawaka Schist - feldspathic muscovite-biotite schist and quartz-diorite gneiss; locally contains lenses of muscovite-graphite schist and amphibolite; commonly cut by feldspathic veins and pegmatites.
Wacoochee Complex; Phelps Creek Gneiss (Precambrian to Paleozoic)
Phelps Creek Gneiss - quartz monzonite to granite gneiss in dikes and sheets with wide migmatite zones at contacts.
Wedowee Group; Wedowee Group undifferentiated (Precambrian to Paleozoic)
Wedowee Group undifferentiated - Wedowee Group undifferentiated includes the Cragford Phyllite and Cutnose Gneiss. Cragford Phyllite -- interbedded fine-grained graphite-chlorite-sericite schist and phyllite, garnet-sericite schist and phyllite, graphite-quartz-sericite phyllite, locally feldspathic biotite gneiss, calc-silicate rock, and quartzite. Cutnose Gneiss -- cyclically interbedded fine-grained quartz-biotite feldspathic gneiss, graphite-chlorite-sericite schist, locally thin interbeds of graphite-quartz-sericite phyllite, and quartzite. Rocks in the area northeast of Clanton in Chilton and Coosa Counties that are here assigned to the Wedowee Group also have been interpreted as part of the Higgins Ferry Group.
Weisner and Wilson Ridge Formations undifferentiated (Cambrian)
Weisner and Wilson Ridge Formations undifferentiated -- interbedded quartzose to slightly feldspathic sandstone and laterally continous conglomerate in ledge-forming units separated by greenish-gray silty mudstone.
Wilcox Group; Hatchetigbee Formation (Eocene)
Hatchetigbee Formation - (Wilcox Group), Light to dark-gray laminated carbonaceous clay, silt and very fine to fine sand, and cross-bedded glauconitic sand; one or more thin beds of fossiliferous marly glauconitic sand and sandstone occur in the upper part. Near the base is a prominent bed of glauconitic calcareous sand containing abundant fossils and spheroidal to pillow-shaped sandstone concretions (Bashi Marl Member). In parts of southeast AL the upper beds of the Th were either eroded or not deposited and the overlying Tt formation directly overlies the Bashi Marl Member.
Wilcox Group; Nanafalia Formation (Paleocene)
Nanafalia Formation - (Wilcox Group), Members of the Nanafalia Formation follow in descending order. Grampian Hills Member - medium-gray massive clay, claystone, sandy fossiliferous clay, and fossiliferous fine sand. "Ostrea thirsae beds" - glauconitic, abundantly fossiliferous, quartzose fine to medium sand. Gravel Creek Sand Member - pale-yellowish-orange to moderate-reddish-brown micaceous cross-bedded fine to very coarse sand containing gravel and clay pebbles in some exposures. Gravel Creek Member is absent locally and near the base may contain thin beds of lignite. Updip deposits in northern Henry County and southern Barbour County include beds of alternating medium-gray and white clay, carbonaceous clay, white and grayish-yellow fine to coarse sand and lenses of bauxite and bauxitic clay. Sand beds commonly are cross-bedded, gravelly, and contain numerous clay pebbles. The sequence of beds is often obscured by weathering and the collapse of beds into sinkholes in the underlying Clayton Formation.
Wilcox Group; Tuscahoma Sand (Paleocene)
Tuscahoma Sand - (Wilcox Group), Light-gray to light-olive-gray laminated and thin-bedded carbonaceous silt and clay interbedded with fine sand; thin lignite beds occur locally. Lower part of the formation includes beds of fossiliferous, glauconitic fine quartz sand containing speroidal sandstone concretions, gravel and clay pebbles.
Zana Granite (Precambrian to Paleozoic)
Zana Granite - quartz monzonite to granite with strong gneissic texture, cut by small pegmatites and aplite dikes, generally elongate; semiconcordant to foliation of country rock.
Arkansas
Arkadelphia Marl (Phanerozoic | Mesozoic | Cretaceous-Late)
Arkadelphia Marl
Atoka Formation, undivided (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Atokan] )
Atoka Formation, undivided
Blakely Sandstone (Middle and Lower Ordovician) (Phanerozoic | Paleozoic | Ordovician-Early Ordovician-Middle)
Blakely Sandstone (Middle and Lower Ordovician)
Bloyd Shale, and Prairie Grove Member of the Hale Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Morrowan])
Bloyd Shale, and Prairie Grove Member of the Hale Formation
Boone Formation (Phanerozoic | Paleozoic | Carboniferous Mississippian-Early [Meramecian Osagean])
Boone Formation
Brownstown Marl (Phanerozoic | Mesozoic | Cretaceous-Late)
Brownstown Marl
Cane Hill Member of Hale Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Early [Morrowan])
Cane Hill Member of Hale Formation
Cason Shale and Fernvale Limestone (Upper Ordovician) and Kimmswick Limestone, Plattin Limestone, and Joachim Dolomite (Middle Ordovician) (Phanerozoic | Paleozoic | Ordovician-Middle Ordovician-Late)
Cason Shale and Fernvale Limestone (Upper Ordovician) and Kimmswick Limestone, Plattin Limestone, and Joachim Dolomite (Middle Ordovician)
Chattanooga Shale (Lower Mississippian and Upper Devonian), Clifty Limestone (Middle Devonian), and Penters Chert (Lower Devonian) (Phanerozoic | Paleozoic | Devonian-Early Devonian-Middle(?) Devonian-Late(?) Carboniferous Mississippian-Early)
Chattanooga Shale (Lower Mississippian and Upper Devonian), Clifty Limestone (Middle Devonian), and Penters Chert (Lower Devonian)
Claibourne Group (Phanerozoic | Cenozoic | Tertiary | Eocene-Middle)
Claibourne Group
Collier Shale (Phanerozoic | Paleozoic | Ordovician-Early)
Collier Shale
Cotter and Jefferson City Dolomites (Phanerozoic | Paleozoic | Ordovician-Early)
Cotter and Jefferson City Dolomites
Crystal Mountain Sandstone (Phanerozoic | Paleozoic | Ordovician-Early)
Crystal Mountain Sandstone
Harthshorne Sandstone (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Des Moinesian])
Harthshorne Sandstone
Igneous rocks (Phanerozoic | Mesozoic | Cretaceous)
Includes undifferentiated altered sedimentary rocks of Paleozoic age at Granite Mountain, Pulaski County, and Mufreesboro, Pike County. Acid to intermediate - Nepheline syenite complexes at Magnet Cove and Potash Sulfur Springs, stocks at Granite Mtn., explosion breccias, and dikes and sills (principally trachyte,tinguaite, phonolite, some ranging from syenite to diabase.) Basic to ultrabasic - Lamproite pipes (Murfreesboro, Pike County) and dikes and sills (principally lamprophyres of fourchite, ouachitite, and monchiquite)
Jackson Group (Phanerozoic | Cenozoic | Tertiary | Eocene-Late)
Jackson Group
Johns Valley Shale (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Early [Morrowan])
Johns Valley Shale
Kiamichi Formation and Goodland Limestone (Phanerozoic | Mesozoic | Cretaceous-Early)
Kiamichi Formation and Goodland Limestone
Mazarn Shale (Phanerozoic | Paleozoic | Ordovician-Early)
Mazarn Shale
McAlester Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Des Moinesian])
McAlester Formation
Midway Group (Phanerozoic | Cenozoic | Tertiary | Paleocene)
Midway Group
Missouri Mountain Shale and Baylock Sandstone (Phanerozoic | Paleozoic | Silurian)
Missouri Mountain Shale and Baylock Sandstone - The Baylock Sandstone is present only in the Cross, Cossatot, and Trap Mountains. Missouri Mountain Shale is mapped with Polk Creek Shale and Bigfork Chert in the area between Paron, Saline County, and Little Rock
Nacatoch Sand (Phanerozoic | Mesozoic | Cretaceous-Late)
Nacatoch Sand
Pitkin Limestone, Fayetteville Shale (including the Wedington Sandstone member), and Batesville Sandstone (including the Hindsville Limestone Member) (Phanerozoic | Paleozoic | Carboniferous Mississippian-Late [Chesterian])
Pitkin Limestone, Fayetteville Shale (including the Wedington Sandstone member), and Batesville Sandstone (including the Hindsville Limestone Member)
Pole Creek Shale (Upper Ordovician) and Bigfork Chert (Upper and Middle Ordovician) (Phanerozoic | Paleozoic | Ordovician-Middle Ordovician-Late)
Polk Creek Shale (Upper Ordovician) and Bigfork Chert (Upper and Middle Ordovician)
Powell Dolomite (Phanerozoic | Paleozoic | Ordovician-Early)
Powell Dolomite
Savanna Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Des Moinesian])
Savanna Formation
Silt and sand (Phanerozoic | Cenozoic | Quaternary | Pleistocene-Early)
Silt and sand - Contains lenses of gravel and clay
Stanley Shale (Phanerozoic | Paleozoic | Carboniferous Mississippian-Early)
Stanley Shale - Includes Chickasaw Creek Chert equivalent of Harlton (1938) near top and Hatton Tuff Lentil and Hot Springs Sandstone Member near base
St. Peter Sanstone and Everton Formation (Middle Ordovician) (Phanerozoic | Paleozoic | Ordovician-Middle)
St. Peter Sanstone and Everton Formation (Middle Ordovician)
Tokio Formation (Phanerozoic | Mesozoic | Cretaceous-Late)
Tokio Formation
Trinity Group (Phanerozoic | Mesozoic | Cretaceous-Early)
Trinity Group
Wilcox Group (Phanerozoic | Cenozoic | Tertiary | Eocene-Early)
Wilcox Group
Womble Shale (Middle Ordovician) (Phanerozoic | Paleozoic | Ordovician-Middle)
Womble Shale (Middle Ordovician)
Woodbine Formation (Phanerozoic | Mesozoic | Cretaceous-Late)
Woodbine Formation
Arizona
Chinle Formation (Late Triassic)
Colorful mudstone, such as in the Painted Desert, and less abundant lenses of sandstone and conglomerate, deposited by a large river system. This unit typically is eroded into badlands topography and contains clays that are prone to shrinking and swelling. (210-230 Ma)
Cretaceous sedimentary rocks (Cretaceous)
Tan sandstone (Dakota Sandstone) overlain by gray shale (Mancos Shale); deposited in beach, river delta, and shallow sea settings. The Mancos Shale is overlain by the Mesaverde Group (map unit Kmv). This unit includes related sandstone and shale exposed near Show Low, Morenci (Pinkard Formation), and around Deer Creek south of Globe. (about 88-97 Ma)
Cretaceous to Late Jurassic sedimentary rocks with minor volcanic rocks (Late Jurassic to Cretaceous)
Sandstone and conglomerate, rarely forms prominent outcrops; massive conglomerate is typical near base of unit and locally in upper part. These deposits are nonmarine except in southeastern Arizona, where prominent gray marine limestone (Mural Limestone) forms the middle of the Bisbee Group. Sandstones are typically medium-bedded, drab brown, lithic-feldspathic arenites. Includes Bisbee Group (largely Early Cretaceous) and related rocks, Temporal, Bathtub, and Sand Wells formations, rocks of Gu Achi, McCoy Mountains Formation, and Upper Cretaceous Fort Crittenden Formation and equivalent rocks. (80-160 Ma)
Early Pleistocene to late Miocene basin deposits (Late Pliocene to Early Pleistocene)
Poorly sorted, variably consolidated gravel and sand that range widely in age. These sediments are generally light gray or tan. This unit is generally mapped in areas of deep late Cenozoic stream incision and landscape degradation where thin Quaternary deposits (map units Qy, Qm, Qo) discontinuously blanket older deposits (map units Tsy or Tsm) and the two cannot be differentiated at the scale of this map. (0.75-10 Ma)
Early Pleistocene to latest Pliocene surficial deposits (Late Pliocene to Early Pleistocene)
Coarse relict alluvial fan deposits that form rounded ridges or flat, isolated surfaces that are moderately to deeply incised by streams. These deposits are generally topographically high and have undergone substantial erosion. Deposits are moderately to strongly consolidated, and commonly contain coarser grained sediment than younger deposits in the same area. (0.75-3 Ma)
Early Proterozoic granitic rocks (Early Proterozoic)
Wide variety of granitic rocks, including granite, granodiorite, tonalite, quartz diorite, diorite, and gabbro. These rocks commonly are characterized by steep, northeast-striking foliation. (1600-1800 Ma)
Early Proterozoic metamorphic rocks (Early Proterozoic)
Undivided metasedimentary, metavolcanic, and gneissic rocks. (1600-1800 Ma)
Early Proterozoic metasedimentary rocks (Early Proterozoic)
Metasedimentary rocks, mostly derived from sandstone and shale, with minor conglomerate and carbonate rock. Includes quartz-rich, mostly nonvolcanic Pinal Schist in southeastern Arizona and variably volcanic-lithic sedimentary rocks in the Yavapai and Tonto Basin supergroups in central Arizona. (1600-1800 Ma)
Early Proterozoic metavolcanic rocks (Early Proterozoic)
Weakly to strongly metamorphosed volcanic rocks. Protoliths include basalt, andesite, dacite, and rhyolite deposited as lava or tuff, related sedimentary rock, and shallow intrusive rock. These rocks, widely exposed in several belts in central Arizona, include metavolcanic rocks in the Yavapai and Tonto Basin supergroups. (1650 to 1800 Ma)
Early Proterozoic quartzite (Early Proterozoic)
Brown to maroon, resistant quartzite and minor conglomerate of the Mazatzal Group, exposed primarily in the Payson area. (1650? -1700 Ma)
Early Tertiary to Late Cretaceous granitic rocks (Late Cretaceous to Early Tertiary)
Porphyritic to equigranular granite to diorite emplaced during the Laramide orogeny. Larger plutons are characteristically medium-grained, biotite +/- hornblende granodiorite to granite. Smaller, shallow-level intrusions are typically porphyritic. Most of the large copper deposits in Arizona are associated with porphyritic granitic rocks of this unit, and are thus named 'porphyry copper deposits'. (50-82 Ma)
Early Tertiary to Late Cretaceous muscovite-bearing granitic rocks (Late Cretaceous to Early Tertiary)
Light-colored peraluminous muscovite granite with or without garnet; commonly forms sills and is associated with abundant pegmatite dikes and sills. This unit includes granites in the Harcuvar and Harquahala Mountains of western Arizona and in the Santa Catalina, Rincon, Tortolita, Picacho, and Coyote Mountains of south-central Arizona. These granites typically represent the youngest phase of voluminous magmatism during the Laramide orogeny in Arizona. This unit also includes several muscovite-bearing granites in southern Arizona that are associated with calc-alkaline granites of unit TKg, and a batholith in the Cabeza Prieta area of southwestern Arizona. (50-80 Ma)
Early Tertiary to Late Cretaceous volcanic rocks (Late Cretaceous to Early Tertiary)
Rhyolite to andesite and closely associated sedimentary and near-surface intrusive rocks; commonly dark gray to dark greenish gray or greenish brown. In the ranges west of Tucson, this unit includes thick welded ash-flow tuffs. Volcanic rocks of this unit are inferred to be derived from vents and volcanoes above magma chambers that solidified to form the granitic rocks of map unit TKg. These rocks are restricted to southeastern Arizona except for a small outcrop near Bagdad. (50-82 Ma)
Glen Canyon Group (Early Jurassic)
Conspicuous red, cross-bedded Wingate Sandstone and the conspicuously cross-bedded, eolian, red to buff Navajo Sandstone form prominent cliffs in northern Arizona. These two sandstone units are separated by variably colored siltstone, silty sandstone, and sandstone of the Kayenta and Moenave Formations. (180-210 Ma)
Holocene river alluvium (Holocene)
Unconsolidated to weakly consolidated sand and gravel in river channels and sand, silt, and clay on floodplains. Also includes young terrace deposits fringing floodplains. (0-10 ka)
Holocene surficial deposits (Holocene)
Unconsolidated deposits associated with modern fluvial systems. This unit consists primarily of fine-grained, well-sorted sediment on alluvial plains, but also includes gravelly channel, terrace, and alluvial fan deposits on middle and upper piedmonts. (0-10 ka)
Holocene to middle Pliocene basaltic rocks (Middle Pliocene to Holocene)
Mostly dark-colored basaltic lava and cinders young enough that some original volcanic landforms are still apparent. Includes a small amount of andesite, dacite, and rhyolite. Rocks of this map unit are largely restricted to six areas widely distributed in Arizona: San Francisco and Uinkaret volcanic fields in northern Arizona (0-4 Ma); Springerville (0-4 Ma) and San Carlos (0-2 Ma) volcanic fields in east-central Arizona; and San Bernardino (0-1 Ma) and Sentinel (1-4 Ma) volcanic fields in southern Arizona. Rocks of this unit are also present in the extreme southwestern part of Arizona where they were erupted at the edge of the Pinacate volcanic field (0-2 Ma) in northwestern Sonora. (0-4 Ma)
Holocene to middle Pliocene volcanic rocks (Middle Pliocene to Holocene)
Rhyolite to andesite deposited as a sequence of lava flows and associated rocks; generally light to medium gray, tan, or reddish brown. These rocks are part of the San Francisco volcanic field. (0-4 Ma)
Jurassic and Triassic sedimentary and volcanic rocks (Triassic and Jurassic)
Undivided massive quartz-feldspar porphyry of the Jurassic Planet Volcanics, quartz-rich metasandstone of the Jurassic Vampire Formation, and quartzite, phyllite, and fine grained, variably calcareous metasiltstone of the Triassic Buckskin Formation; exposed primarily in the Buckskin and Rawhide Mountains of western Arizona. This unit also includes sandstone and conglomerate beneath Jurassic volcanic rocks in the central Dome Rock Mountains. (160-240 Ma)
Jurassic granitic rocks (Jurassic)
Granite to diorite, locally foliated and locally alkalic; includes Triassic(?) granitoids in the Trigo Mountains. This unit includes two dominant assemblages of igneous rocks. The Kitt Peak-Trigo Peaks superunit includes, from oldest to youngest: dark, foliated or gneissic diorite, medium-grained equigranular to porphyritic granodiorite, and small, irregular intrusions of light-colored, fine-grained granite. The Ko Vaya superunit, limited to south-central Arizona, includes texturally heterogeneous K-feldspar-rich granitic rocks. (150-180 Ma)
Jurassic sedimentary and volcanic rocks (Jurassic)
Sandstone and conglomerate derived from volcanic rocks with associated intermediate-composition lava flows, breccias, and tuffs. In southern Arizona this unit includes rocks of the Artesa sequence, Pitoikam Formation, Mulberry Wash volcanics, Rudolfo Red Beds, Recreation Red Beds, and Gardner Canyon Formation. In western Arizona it includes the Harquar Formation, rocks of Slumgullion, and related(?) unnamed units in the Kofa and Middle Mountains. This unit is characterized by maroon, brown, and purplish-gray volcanic-lithic sandstone and siltstone, with subordinate to abundant conglomerate, quartz-rich sandstone and sparse limestone. (150-170 Ma)
Jurassic to Cambrian metamorphosed sedimentary rocks (Cambrian to Jurassic)
Highly faulted and folded rocks of units Jv, J_, and Pz, deformed and metamorphosed in Jurassic, Cretaceous and Tertiary time. This unit is restricted to west-central Arizona. (160-540 Ma)
Jurassic volcanic rocks (Jurassic)
Massive quartz-feldspar porphyry, generally interpreted as thick, welded rhyolitic tuffs, with locally abundant lava, and sandstone and conglomerate derived from volcanic rocks. Rare eolian quartzite units are interbedded in southern Arizona. Includes Ali Molina Formation, Mount Wrightson Formation, part of the Canelo Hills Volcanics, Cobre Ridge tuff, Black Rock volcanics, Planet Volcanics, and equivalent rocks. (160-200 Ma)
Late and middle Pleistocene surficial deposits (Middle to Late Pleistocene)
Unconsolidated to weakly consolidated alluvial fan, terrace, and basin-floor deposits with moderate to strong soil development. Fan and terrace deposits are primarily poorly sorted, moderately bedded gravel and sand, and basin-floor deposits are primarily sand, silt, and clay. (10-750 ka)
Late to middle Miocene basaltic rocks (Middle to Late Miocene)
Mostly dark, mesa-forming basalt deposited as lava flows. Rocks of this unit are widely exposed south of Camp Verde (Hickey Formation basalts), in the Mohon Mountains north of Bagdad, "The Mesa" east of Parker, and at other scattered locations in western Arizona. Rocks of this unit were not tilted by middle-Tertiary normal faulting except in a narrow belt from north of Phoenix to the northwest corner of the state. (8-16 Ma)
Middle Miocene to Oligocene granitic rocks (Oligocene to Middle Miocene)
Granite to diorite representing solidified magma chambers that were the likely source of overlying and nearby volcanic rocks of map unit Tv. The granitic rocks are typically equigranular and fine- to medium-grained. (14-26 Ma)
Middle Miocene to Oligocene sedimentary rocks (Oligocene to Middle Miocene)
Con-glomerate, sandstone, mudstone, limestone, and rock-avalanche breccia (sheet-like deposits of crushed rock) deposited and tilted during widespread normal faulting and basin development. Sediments, mostly conglomerate and sandstone, are commonly medium to dark brown, reddish brown, or brownish gray; younger strata are generally lighter colors. Most deposits are 20 to 30 Ma in southeastern Arizona and 15 to 25 Ma in central and western Arizona. (11-32 Ma)
Middle Miocene to Oligocene shallow intrusions (Oligocene to Middle Miocene)
Generally very fine-grained, porphyritic rhyolite to dacite in small, irregular-shaped bodies formed as subvolcanic intrusions in volcanic fields of southern and western Arizona, or in concentrated zones of dikes in the Mohave and Black Mountains of northwestern Arizona. The unit consists of mafic tuff, breccia and shallow intrusions at Buell Park in northeastern Arizona. (14-35 Ma)
Middle Miocene to Oligocene volcanic and sedimentary rocks, undivided (Oligocene to Middle Miocene)
Sequences of diverse volcanic rocks with abundant interbedded sedimentary rocks. (11-32 Ma)
Middle Miocene to Oligocene volcanic rocks (Oligocene to Middle Miocene)
Lava, tuff, fine-grained intrusive rock, and diverse pyroclastic rocks. These compositionally variable volcanic rocks include basalt, andesite, dacite, and rhyolite. Thick felsic volcanic sequences form prominent cliffs and range fronts in the Black (Mohave County), Superstition, Kofa, Eagletail, Galiuro, and Chiricahua Mountains. This unit includes regionally extensive ash-flow tuffs, such as the Peach Springs tuff of northwestern Arizona and the Apache Leap tuff east of Phoenix. Most volcanic rocks are 20-30 Ma in southeastern Arizona and 15 to 25 Ma in central and western Arizona, but this unit includes some late Eocene rocks near the New Mexico border in east-central Arizona. (11-38 Ma)
Middle Proterozoic diabase (Middle Proterozoic)
Dark gray to black sills (intrusions mostly parallel to bedding) in strata of the Apache Group and irregular to sheet-like intrusions in other rocks. Present in east-central and southeastern Arizona. Some sills are more than 100 m thick. Exposures are extensive north of Globe. (1050-1150 Ma)
Middle Proterozoic granitic rocks (Middle Proterozoic)
Mostly porphyritic biotite granite with large microcline phenocrysts, with local fine-grained border phases and aplite. Associated pegmatite and quartz veins are rare. This unit forms large plutons, including the Oracle Granite, Ruin Granite, granite in the Pinnacle Peak - Carefree area northeast of Phoenix, and several bodies west of Prescott. (1400-1450 Ma)
Middle Proterozoic sedimentary rocks (Middle Proterozoic)
Red-brown shale and sandstone, buff to orange quartzite, limestone, basalt, black shale, and sparse conglomerate. This unit includes the Grand Canyon Supergroup, Apache Group, and Troy Quartzite. These rocks were deposited in shallow marine, coastal nonmarine, and fluvial settings. (700-1300)
Mississippian, Devonian, and Cambrian sedimentary rocks (Cambrian, Devonian, and Mississippian)
Brown to dark gray sandstone grades upward into green and gray shale, overlain by light to medium gray or tan limestone and dolostone. This unit includes the Tapeats Sandstone, Bright Angel Shale, Muav Limestone, Temple Butte Formation and Redwall Limestone in northern Arizona, and the Bolsa Quartzite, Abrigo Formation, Martin Formation, and Escabrosa Limestone in southern Arizona. These rocks record intermittent sea-level rise and inundation in early Paleozoic time. (330-540 Ma)
Moenkopi Formation (Early and Middle(?) Triassic)
Dark red sandstone and mudstone; includes gypsum beds in northwestern Arizona; deposited on a low-relief coastal plain. (230-245 Ma)
Morrison Formation (Late Jurassic)
Commonly cliff-forming, cross-bedded sandstone lenses alternating with slope-forming siltstone, mudstone and shale. Colors are highly variable, and include greenish gray, reddish brown, pink, white, and purple. Sands were deposited by braided streams with finer sediment representing overbank or lacustrine deposits. (145-160 Ma)
Oligocene to Paleocene[?] sedimentary rocks (Paleocene(?) to Oligocene)
Light colored, weakly to moderately consolidated conglomerate and sandstone deposited largely or entirely before mid-Tertiary volcanism and extensional faulting. Most sediment was deposited by early Cenozoic streams that flowed northeastward onto the Colorado Plateau from areas to the southwest that are now lower in elevation than the Plateau. Sediments of this map unit, other than the Chuska Sandstone in northeasternmost Arizona, are commonly referred to as "rim gravels" because they now rest on or near the Mogollon Rim, which is the southwestern edge of the Colorado Plateau. (30-65 Ma)
Orocopia Schist (Late Cretaceous to Early Tertiary)
Mostly gray, fine-grained quartz-feldspar-mica schist, with sparse metabasalt and metachert. The unit is exposed in tectonic windows in the southwestern corner of Arizona. It is interpreted as metamorphosed marine sandstone that was tectonically emplaced beneath southwestern Arizona during early Tertiary subduction of Pacific Ocean sea floor. (65-165 Ma)
Paleozoic sedimentary rocks (Paleozoic)
Undivided Paleozoic limestone, dolostone, quartzite, shale, and related sedimentary rocks. (248-544 Ma)
Permian sedimentary rocks (Permian)
Gray to tan, cherty limestone of Kaibab and Toroweap Formations, and underlying white to tan, fine-grained Coconino Sandstone. Limestone was deposited in a shallow sea, and sandstone was deposited in near-shore dunes and beach settings. (270-280 Ma)
Permian to Pennsylvanian sedimentary rocks (Pennsylvanian to Permian)
Interbedded sandstone, shale, and limestone usually characterized by ledgy outcrops. Orange to reddish sandstone forms cliffs near Sedona. This unit includes Supai Group and Hermit Shale in northern Arizona and Naco Group in southern Arizona. It was deposited in coastal-plain to shallow-marine settings during time of variable and changing sea level. Rocks of this map unit in southern Arizona may be in part equivalent to Permian rocks of map unit P in central and northern Arizona. (280-310 Ma)
Pliocene to late Miocene basaltic rocks (Late Miocene to Pliocene)
Mostly dark, inconspicuously flat, low-lying or mesa-forming basalt deposited as lava flows. Rocks included in this unit are located almost entirely in the large volcanic fields south and west of Flagstaff, in smaller fields in northwesternmost Arizona, and in the Hopi Buttes volcanic field on the Navajo and Hopi Indian Reservations north of Holbrook. Original volcanic landforms have been obscured by erosion. (4-8 Ma)
Pliocene to middle Miocene deposits (Middle Miocene to Pliocene)
Moderately to strongly consolidated conglomerate and sandstone deposited in basins during and after late Tertiary faulting. Includes lesser amounts of mudstone, siltstone, limestone, and gypsum. These deposits are generally light gray or tan. They commonly form high rounded hills and ridges in modern basins, and locally form prominent bluffs. Deposits of this unit are widely exposed in the dissected basins of southeastern and central Arizona. (2-16 Ma)
Pliocene to middle Miocene volcanic rocks (Middle Miocene to Pliocene)
Rhyolite to andesite deposited as lava flows and related rocks associated with basaltic rocks of map units Tby and Tb. (2-12 Ma)
Proterozoic granitic rocks (Proterozoic)
Undivided Early and Middle Proterozoic granitic rocks (units Xg and Yg). (1400-1800 Ma)
Quaternary surficial deposits, undivided (Quaternary)
Unconsolidated to strongly consolidated alluvial and eolian deposits. This unit includes: coarse, poorly sorted alluvial fan and terrace deposits on middle and upper piedmonts and along large drainages; sand, silt and clay on alluvial plains and playas; and wind-blown sand deposits. (0-2 Ma)
San Rafael Group (Middle to Late Jurassic)
Commonly cross-bedded, ledge-forming sandstone and slope-forming siltstone. Rock typically has a striped red and white aspect. The Carmel Formation and Entrada Sandstone are prominent members of this group. (Late to Middle Jurassic, about 160-180 Ma)
Sedimentary rocks of the Late Cretaceous Mesaverde Group (Late Cretaceous)
Gray to buff sandstone with interbedded shale and coal. These rocks, which are similar to slightly younger rocks that form Mesa Verde in southwestern Colorado, were deposited on the margin of a shallow sea. Rocks of this map unit host the only large coal deposits in Arizona. (84-88 Ma)
Shinarump Conglomerate Member, Chinle Formation (Late Triassic)
Basal conglomerate and pebbly sandstone of the Chinle Formation is relatively resistant to erosion and forms extensive benches in some parts of the Colorado Plateau. (210-230 Ma)
Tertiary to Early Proterozoic gneissic rocks (Early Proterozoic to Tertiary)
Gneissic rocks with complex histories, typically with well developed, light-colored granitoid layers and dark-colored biotite- and amphibole-rich layers. Protoliths are of Tertiary to Proterozoic age. This unit includes variably mylonitic gneisses in metamorphic core complexes that have been exhumed from middle crustal levels by large-displacement middle Tertiary normal faults, and gneiss exposed at scattered locations near the Colorado River in southwestern Arizona. These rocks are interpreted to record Proterozoic, Mesozoic, and Tertiary metamorphism and deformation. (15-1800 Ma)
California
Cambrian marine rocks (Late Proterozoic to Middle Devonian)
Sandstone, shale, limestone, dolomite, chert, quartzite, and phyllite; includes some rocks that are possibly Precambrian
Carboniferous marine rocks, unit 1 (Western Mojave Desert) (Late Proterozoic to Pennsylvanian)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Carboniferous marine rocks, unit 2 (SE California Carbonate Assemblage) (Mississippian to Early Permian)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Carboniferous marine rocks, unit 3 (SE California Clastic Assemblage) (Late Devonian to Early Permian)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Carboniferous marine rocks, unit 4 (Eastern Klamath Mountains) (Mississippian to Early Permian)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Carboniferous marine rocks, unit 6 (Northeastern Sierra Nevada) (Mississippian to Early Permian)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Carboniferous marine rocks, unit 7 (Bishop) (Mississippian to Early Permian)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Carboniferous marine rocks, unit 8 (Mono Lake) (Ordovician to Devonian)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Cenozoic (Tertiary) granitic rocks, unit 1 (Death Valley) (middle to late Miocene)
Cenozoic (Tertiary) granitic rocks--quartz monzonite, quartz latite, and minor monzonite, granodiorite, and granite; found in the Kingston, Panamint, Amargosa, and Greenwater Ranges in southeastern California.
Cretaceous marine rocks (in part nonmarine) (?), unit 1 (Blythe) (Middle Jurassic(?) to Late Cretaceous)
Undivided Cretaceous sandstone, shale, and conglomerate; minor nonmarine rocks in Peninsular Ranges (?)
Cretaceous marine rocks (in part nonmarine), unit 1 (Coast Ranges) (Early to Late Cretaceous)
Undivided Cretaceous sandstone, shale, and conglomerate; minor nonmarine rocks in Peninsular Ranges
Cretaceous marine rocks (in part nonmarine), unit 2 (West Walker River) (Triassic(?) and/or Jurassic(?))
Undivided Cretaceous sandstone, shale, and conglomerate; minor nonmarine rocks in Peninsular Ranges
Cretaceous marine rocks (in part nonmarine), unit 3 (Mescal Range) (Middle Jurassic to late Early Cretaceous)
Undivided Cretaceous sandstone, shale, and conglomerate; minor nonmarine rocks in Peninsular Ranges
Devonian marine rocks, unit 1 (Death Valley) (Middle to Late Devonian)
Limestone and dolomite, sandstone and shale; in part tuffaceous
Devonian marine rocks, unit 2 (Eastern Klamath Mountains) (Devonian)
Limestone and dolomite, sandstone and shale; in part tuffaceous
Eocene and Paleocene marine rocks, undivided (Paleocene to middle Eocene)
Eocene marine rocks (Paleocene to Oligocene)
Shale, sandstone, conglomerate, and minor limestone; in part Oligocene and Paleocene.
Eocene nonmarine rocks, unit 1 (Northern and Central California) (Eocene)
Sandstone, shale, and conglomerate.
Franciscan Complex, unit 1 (Coast Ranges) (Jurassic to Cretaceous)
Franciscan complex: Cretaceous and Jurassic sandstone with smaller amounts of shale, chert, limestone, and conglomerate. Includes Franciscan melange, except where separated--see KJfm.
Franciscan schist (Early Cretaceous)
Blueschist and semi-schist of Franciscan complex
Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains) (Triassic to Late Jurassic)
Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks
Jurassic marine rocks, unit 2 (Coast Ranges) (Late Jurassic to Early Cretaceous)
Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks
Jurassic marine rocks, unit 4 (Peninsular Ranges and Western Transverse Ranges) (Paleozoic(?) to Late Jurassic)
Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks
Jurassic marine rocks, unit 5 (Northern Sierra Nevada and Eastern Klamath Mountains) (Devonian to Late Jurassic)
Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks
Jurassic marine rocks, unit 6 (Mono Lake) (Ordovician(?) to Triassic(?))
Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks
Limestone of probable Paleozoic or Mesozoic age (Paleozoic to Mesozoic)
Limestone, dolomite, and marble whose age is uncertain but probably Paleozoic or Mesozoic
Lower Cretaceous marine rocks (Early Cretaceous)
Lower Cretaceous sandstone, shale, and conglomerate
Lower Cretaceous marine rocks (?) (Cretaceous (?))
Lower Cretaceous sandstone, shale, and conglomerate (?)
Mesozoic granitic rocks, unit 1 (Salinian Block) (Early to Late Cretaceous)
Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite
Mesozoic granitic rocks , unit 2 (Peninsular Ranges) (Middle Jurassic to Late Cretaceous)
Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite
Mesozoic granitic rocks, unit 3 (Sierra Nevada, Death Valley area, Northern Mojave Desert and Transverse Ranges) (Permian to Tertiary; most Mesozoic)
Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite
Mesozoic granitic rocks, unit 4 (Klamath Mountains and Northern Sierra Nevada) (Devonian)
Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite
Mesozoic granitic rocks, unit 5 (Klamath Mountains) (Jurassic to early Cretaceous)
Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite
Mesozoic volcanic rocks, unit 1 (Coast Ranges) (Jurassic to Cretaceous)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains) (Jurassic)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Mesozoic volcanic rocks, unit 3 (Mojave Desert, Death Valley area, and Eastern Sierra Nevada) (Triassic to Cretaceous)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Mesozoic volcanic rocks, unit 4 (Peninsular Ranges) (Late Jurassic to Early Cretaceous)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Mesozoic volcanic rocks, unit 5 (Northern Sierra Nevada and Eastern Klamath Mountains) (Late Permian(?) to Jurassic)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Miocene marine rocks (Oligocene to Pliocene)
Sandstone, shale, siltstone, conglomerate and breccia; in part Pliocene and Oligocene.
Miocene marine rocks and Franciscan schist (Cretaceous(?) to Miocene)
Miocene nonmarine rocks (Oligocene to Pleistocene)
Sandstone, shale, conglomerate, and fanglomerate; in part Pliocene and Oligocene.
Oligocene marine rocks (Eocene to Miocene)
Sandstone, shale, and conglomerate; in part Miocene and Eocene.
Oligocene nonmarine rocks, unit 1 (Northern California) (Oligocene to Miocene)
Sandstone, shale, and conglomerate; in part Miocene and Eocene.
Oligocene nonmarine rocks, unit 2 (Central and Southern California) (middle Eocene to early Miocene)
Sandstone, shale, and conglomerate; in part Miocene and Eocene.
Paleocene marine rocks, unit 1 (Central and Southern California) (Paleocene)
Sandstone, shale, and conglomerate; mostly well consolidated
Paleocene marine rocks, unit 2 (Northern California) (Paleocene to late Eocene)
Sandstone, shale, and conglomerate; mostly well consolidated
Paleocene marine rocks, unit 3 (La Panza Range) (Late Cretaceous(?) to Eocene(?))
Sandstone, shale, and conglomerate; mostly well consolidated
Paleozoic and Permo-Triassic granitic rocks, unit 1 (Eastern Klamath Mountains) (Permian)
Paleozoic and Permo-Triassic granitic rocks in the San Gabriel and Klamath Mountains
Paleozoic and Permo-Triassic granitic rocks unit 2 (San Gabriel Mountains) (Late Triassic)
Paleozoic and Permo-Triassic granitic rocks in the San Gabriel and Klamath Mountains
Paleozoic marine rocks, undivided, unit 1 (Mojave Desert and Death Valley area) (Late Proterozoic to Jurassic)
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 2 (Northern Mojave Desert and Southeastern Sierra Nevada) (Cambrian to Jurassic)
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 3 (Eastern Sierra Nevada) (Late Proterozoic(?) to Mesozoic(?))
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 4 (Western Sierra Nevada) (Ordovician to Triassic)
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 5 (Northeastern Sierra Nevada) (Ordovician to Jurassic)
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 6 (Northwestern Sierra Nevada) (Permian(?) to Jurassic(?))
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 9 (Western Klamath Mountains) (Devonian to Jurassic)
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic metavolcanic rocks, unit 1 (Eastern Klamath Mountains) (Devonian and Permian)
Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks
Paleozoic metavolcanic rocks, unit 2 (Northeastern Sierra Nevada) (Devonian and Permian)
Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks
Paleozoic metavolcanic rocks, unit 3 (Northwestern Sierra Nevada) (Permian to Jurassic)
Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks
Paleozoic metavolcanic rocks, unit 5 (Mono Lake) (Triassic to Jurassic)
Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks
Permian marine sedimentary rocks, unit 1 (Death Valley and Mojave Desert) (Pennsylvanian to Triassic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Permian marine sedimentary rocks, unit 2 (Northwestern Sierra Nevada) (Paleozoic or Mesozoic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Permian marine sedimentary rocks, unit 3 (Northeastern Sierra Nevada) (Early to Late Permian)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Pliocene marine rocks (Miocene to Pleistocene)
Sandstone, siltstone, shale, and conglomerate; in part Pleistocene and Miocene.
Plio-Pleistocene and Pliocene loosely consolidated deposits (Miocene to Pleistocene)
Pliocene and/or Pleistocene sandstone, shale, and gravel deposits; in part Miocene.
Precambrian granitic rocks, unit 1 (Eastern Mojave Desert) (Early Proterozoic to Miocene)
Precambrian granite, syenite, anorthosite, and gabbroic rocks in the San Gabriel Mountains; also various Precambrian plutonic rocks elsewhere in southeastern California
Precambrian granitic rocks, unit 2, (San Gabriel Mountains Anorthosite) (Middle Proterozoic)
Precambrian granite, syenite, anorthosite, and gabbroic rocks in the San Gabriel Mountains; also various Precambrian plutonic rocks elsewhere in southeastern California
Precambrian igneous and metamorphic rock complex (Early Proterozoic to Miocene)
Complex of Precambrian igneous and metamorphic rocks. Mostly gneiss and schist intruded by igneous rocks; may be Mesozoic in part.
Precambrian rocks, undivided, unit 1 (Death Valley) (Early Proterozoic to Mesozoic)
Conglomerate, shale, sandstone, limestone, dolomite, marble, gneiss, hornfels, and quartzite; may be Paleozoic in part
Precambrian rocks, undivided, unit 2 (Mojave Desert and Transverse Ranges) (Early Proterozoic to Miocene)
Conglomerate, shale, sandstone, limestone, dolomite, marble, gneiss, hornfels, and quartzite; may be Paleozoic in part
pre-Cenozoic granitic and metamorphic rocks undivided (Early Proterozoic to Late Cretaceous)
Granitic and metamorphic rocks, mostly gneiss and other metamorphic rocks injected by granitic rocks. Mesozoic to Precambrian.
pre-Cenozoic metasedimentary and metavolcanic rocks undivided (Early Proterozoic to Cretaceous)
Undivided pre-Cenozoic metasedimentary and metavolcanic rocks of great variety. Mostly slate, quartzite, hornfels, chert, phyllite, mylonite, schist, gneiss, and minor marble.
Quaternary alluvium and marine deposits (Pliocene to Holocene)
Alluvium, lake, playa, and terrace deposits; unconsolidated and semi-consolidated. Mostly nonmarine, but includes marine deposits near the coast.
Quaternary pyroclastic and volcanic mudflow deposits, unit 1 (Cascade Volcanic Field) (Quaternary)
Quaternary pyroclastic and volcanic mudflow deposits.
Quaternary pyroclastic and volcanic mudflow deposits, unit 1, questionably identified (Cascade Volcanic Field) (Quaternary)
Quaternary pyroclastic and volcanic mudflow deposits.
Quaternary pyroclastic and volcanic mudflow deposits, unit 2 (Long Valley Caldera) (Quaternary (0-1 Ma))
Quaternary pyroclastic and volcanic mudflow deposits.
Quaternary pyroclastic and volcanic mudflow deposits, unit 3 (Sutter Buttes) (Quaternary (1.5-2.5 Ma))
Quaternary pyroclastic and volcanic mudflow deposits.
Quaternary sand deposits, unit 2 (inland) (Quaternary)
Extensive marine and nonmarine sand deposits, generally near the coast or desert playas
Quaternary volcanic flow rocks, unit 1 (Cascade Volcanic Field) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 1, questionably identified (Cascade Volcanic Field) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 2 (Long Valley Caldera) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 3 (Clear Lake Volcanic Field) (Quaternary (0-4 Ma))
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 4 (Sutter Buttes) (Quaternary (1.5-2.5 Ma))
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 5 (Coso Volcanic Field) (Quaternary (0-4 Ma))
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 7 (Mojave Desert) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 7, questionably identified (Mojave Desert) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Recent (Holocene) pyroclastic and volcanic mudflow deposits, unit 1 (Cascade Volcanic Field) (Holocene)
Recent (Holocene) pyroclastic and volcanic mudflow deposits; in part Pleistocene.
Recent (Holocene) pyroclastic and volcanic mudflow deposits, unit 2 (Mono Craters) (Holocene)
Recent (Holocene) pyroclastic and volcanic mudflow deposits; in part Pleistocene.
Schist of various types and ages, unit 1 (Peninsular Ranges) (Triassic(?))
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian
Schist of various types and ages, unit 2 (Southern and West-central California) (Late Cretaceous to Eocene)
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Schist of various types and ages, unit 3 (Santa Cruz Island) (Jurassic)
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Schist of various types and ages, unit 5 (Slate Range) (Mesozoic)
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Schist of various types and ages, unit 6 (Santa Cruz Mountains) (Paleozoic or Mesozoic)
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Schist of various types and ages, unit 7 (Klamath Mountains) (Devonian)
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Schist of various types and ages, unit 8 (Condrey Mountain) (Jurassic(?))
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Schist of various types and ages, unit 9 (Cargo Muchacho Mountains) (Jurassic(?))
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Silurian and/or Ordovician marine rocks, unit 1 (Death Valley) (Ordovician to Early Devonian)
Sandstone, shale, conglomerate, chert, slate, quartzite, hornfels, marble, dolomite, phyllite; some greenstone
Silurian and/or Ordovician marine rocks, unit 2 (Bishop) (Late Cambrian(?) to Early Permian(?))
Sandstone, shale, conglomerate, chert, slate, quartzite, hornfels, marble, dolomite, phyllite; some greenstone
Silurian and/or Ordovician marine rocks, unit 3 (Eastern Klamath Mountains) (Ordovician to Early Devonian)
Sandstone, shale, conglomerate, chert, slate, quartzite, hornfels, marble, dolomite, phyllite; some greenstone
Silurian and/or Ordovician marine rocks, unit 4 (Northern Sierra Nevada) (Ordovician to Devonian)
Sandstone, shale, conglomerate, chert, slate, quartzite, hornfels, marble, dolomite, phyllite; some greenstone
Tertiary-Cretaceous Coastal Belt Rocks (Late Cretaceous to Pliocene)
Sandstone, shale and minor conglomerate in coastal belt of northwestern California; included by some in Franciscan Complex. Previously considered Cretaceous, but now known to contain early Tertiary microfossils in places.
Tertiary intrusive rocks (hypabyssal), unit 1 (Cascades Volcanic Field) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 2 (Quien Sabe Volcanic Field) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 4 (Tranquillon-Obispo) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 5 (Southern California Basin) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 6 (Southern Mojave Desert) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 7 (Northern Mojave Desert) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary nonmarine rocks, undivided (Paleocene to Pliocene)
Undivided Tertiary sandstone, shale, conglomerate, breccia, and ancient lake deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 1 (Sonoma Volcanic Field) (Tertiary (3-7 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 2 (Berkeley Hills) (Tertiary (8-12 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 3 (Pinnacles-Neenach) (Tertiary (22-24 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 4 (Tranquillon-Obispo) (Tertiary (16-18 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 5 (Southern California Basin) (Tertiary (8-25 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 6 (Jacumba) (Tertiary (12-19 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 7 (Southern Mojave Desert) (Tertiary (8-28 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 8 (Northern Mojave Desert) (Tertiary (4-22 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 9 (Cascade Range) (Tertiary (2-24 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary volcanic flow rocks, unit 10 (Alverson) (Tertiary (14-18 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 11 (Jacumba) (Tertiary (12-19 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 12 (Sam Emigdio) (Tertiary (22-25 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 13 (Plush Ranch-Vasquez-Diligencia) (Tertiary (19-23 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 14 (Tranquillon-Obispo) (Tertiary (16-18 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 15 (Southern Mojave Desert) (Tertiary (8-28 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 16 (Northern Mojave Desert) (Tertiary (4-22 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 17 (Cascade Range) (Tertiary (2-24 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 18 (San Joaquin-Kings Canyon) (Tertiary (3-4 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 1 (Quien Sabe-Burdell Mountain) (Tertiary (9.5-13 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 2 (Pinnacles-Neenach) (Tertiary (22-24 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 3 (Sonoma Volcanic Field) (Tertiary (3-7 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 4 (Berkeley Hills) (Tertiary (8-12 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 6 (Page Mill-Mindego) (Tertiary (12-15 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 8 (Southern California Basin) (Tertiary (8-25 Ma; most near 15))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Triassic marine rocks, unit 1 (Death Valley area and Mojave Desert) (Early to Middle Triassic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Triassic marine rocks, unit 2 (Eastern Klamath Mountains) (Middle to Late Triassic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Triassic marine rocks, unit 3 (Lake Almanor) (Permian to Jurassic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Triassic marine rocks, unit 4 (West Walker River) (Triassic(?))
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Triassic marine rocks, unit 5 (Northern Sierra Nevada) (Middle to Late Triassic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Triassic marine rocks, unit 6 (Southern Sierra Nevada) (Late Triassic to Early Jurassic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Triassic marine rocks, unit 7 (Mono Lake) (Paleozoic or Mesozoic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Ultramafic rocks, chiefly Mesozoic, unit 1 (Trinity Ophiolite) (Ordovician)
Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 1
Ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains) (Late Proterozoic(?) to Early Jurassic)
Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 2
Undivided pre-Cenozoic metavolcanic rocks, unit 1 (Southwestern Sierra Nevada) (Ordovician(?) to Permian(?))
Undivided pre-Cenozoic metavolcanic rocks. Includes latite, dacite, tuff, and greenstone; commonly schistose.
Undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided) (Paleozoic(?) to Mesozoic(?))
Undivided pre-Cenozoic metavolcanic rocks. Includes latite, dacite, tuff, and greenstone; commonly schistose.
Upper Cretaceous and Paleocene marine rocks, undivided (Late Cretaceous to Paleocene)
Sandstone, shale, and conglomerate
Upper Cretaceous marine rocks (?) (Cretaceous)
Upper Cretaceous sandstone, shale, and conglomerate (?)
Upper Cretaceous marine rocks, unit 1 (Upper Great Valley Sequence) (Late Cretaceous)
Upper Cretaceous sandstone, shale, and conglomerate
Upper Cretaceous marine rocks, unit 2 (Klamath Mountains) (late Early to Late Cretaceous)
Upper Cretaceous sandstone, shale, and conglomerate
Colorado
Alkalic and mafic rocks in small plutons, and diabase and gabbro dikes (Proterozoic | Mesoproterozoic)
Alkalic and mafic rocks in small plutons, and diabase and gabbro dikes
Animas Fm (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary)
Arkosic sandstone, shale, and conglomerate; contains abundant volcanic materials; Upper Cretaceous volcaniclastic McDermott Member at base
Arikaree Fm (Phanerozoic | Cenozoic | Tertiary)
Sandstone; contains abundant volcanically derived material
Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary)
Includes basalts of Hinsdale Fm in San Juan Mountains - Servilleta Fm in San Luis Valley and many other occurrences
Belden Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Shale, limestone, and sandstone. Includes Kerber Fm in south-central
Biotitic gneiss, schist, and migmatite (Proterozoic | Paleoproterozoic)
Locally contains minor hornblende gneiss, calc-silicate rock, quartzite, and marble. Derived principally from sedimentary rocks
Chinle and Chugwater Fms (Phanerozoic | Mesozoic | Triassic)
Chinle Fm (Phanerozoic | Mesozoic | Triassic)
Red siltstone, sandstone, and limestone-pellet conglomerate
Chinle, Moenkopi, and Park City Fms (Phanerozoic | Paleozoic Mesozoic | Permian Triassic)
Red and gray siltstone, shale, and sandstone
Chugwater Fm (Phanerozoic | Mesozoic | Triassic)
Red sandstone, siltstone, shale, and local limestone and gypsum
Coalmont Fm (Phanerozoic | Cenozoic | Tertiary)
Arkosic sandstone, conglomerate, and shale; coal in lower part; in North Park
Cutler Fm (Phanerozoic | Paleozoic | Permian)
Arkosic sandstone, siltstone, and conglomerate
Dakota and Morrison Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous)
Dakota, Burro Canyon, Morrison, and Junction Creek Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous)
Burro Canyon is locally absent
Dakota, Burro Canyon, Morrison, and Wanakah Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous)
Dakota, Purgatoire, Morrison, Ralston Creek, and Entrada Fms in southeast. Dakota, Morrison, and Entrada Fms in central mountains. Dakota, Burro Canyon, Morrison, Wanakah, and Entrada Fms in Gunnison River area. Dakota, Morriso (Phanerozoic | Mesozoic | Jurassic Cretaceous)
Dakota Sandstone and Burro Canyon Fm (Phanerozoic | Mesozoic | Cretaceous)
Sandstone, shale, and conglomerate. In northwest and west-central: Lower Cretaceous. In southwest: Lower and Upper Cretaceous.
Denver and Arapahoe Fms (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary)
Sandstone, mudstone, claystone, and conglomerate; Denver is characterized by andesitic materials
Denver Fm or lower part of Dawson Arkose (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary)
Arkosic sandstone, shale, mudstone, conglomerate, and local coal beds
Dockum Group (Phanerozoic | Mesozoic | Triassic)
Red sandstone, siltstone, and local limestone
Dolores Fm (Phanerozoic | Mesozoic | Triassic)
Red siltstone, shale, sandstone, and limestone-pellet conglomerate
Dolores Fm and Cutler Fm (Phanerozoic | Paleozoic Mesozoic | Permian Triassic)
Red siltstone, sandstone, and conglomerate
Dry Union Fm (Phanerozoic | Cenozoic | Tertiary)
Siltstone, sandstone, and conglomerate. Includes Wagontongue Fm (Miocene) in South Park
Eagle Valley Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Siltstone, shale, and local gypsum
Eagle Valley Fm - evaporitic facies (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Gypsum, siltstone, and shale; salt present in deep borings. Intertongues with Minturn and Lower Maroon Fms. Diapiric structure in many places
Eocene prevolcanic sedimentary rocks (Phanerozoic | Cenozoic | Tertiary)
South-central: Arkosic sand and bouldery gravel of Echo Park Alluvium. Southwest: includes Telluride Conglomerate and Blanco Basin Fm (arkosic mudstone, sandstone, and conglomerate)
Eolian deposits (Phanerozoic | Cenozoic | Quaternary)
Includes dune sand and silt and Peoria Loess
Evaporitic facies of Minturn And Belden Fms in South Park and southward (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Gypsum, siltstone, and shale
Felsic and hornblendic gneisses, either separate or interlayered (Proterozoic | Paleoproterozoic)
Includes metabasalt, metatuff, and interbedded metagraywacke; locally contains interlayered biotite gneiss. Derived principally from volcanic rocks
Fort Union Fm (Phanerozoic | Cenozoic | Tertiary)
Shale, sandstone, and local coal beds
Frontier Sandstone and Mowry Shale Members of Mancos Shale, and Dakota Sandstone (Phanerozoic | Mesozoic | Cretaceous)
Locally includes, at base, Burro Canyon Fm (shale and sandstone) or, in western Moffat County, Cedar Mountain Fm (conglomerate and shale)
Glen Canyon Group and Chinle Fm (Phanerozoic | Mesozoic | Triassic Jurassic)
In southwest, Glen Canyon Group consists of Navajo Sandstone, Kayenta Fm (red siltstone, shale, and sandstone) and Wingate Sandstone; Chinle is red siltstone
Granitic rocks of 1400-m.y. age group (Proterozoic | Mesoproterozoic)
Includes Silver Plume, Sherman, Cripple Creek, St. Kevin, Vernal Mesa, Curecanti, Eolus, and Trimble Granites or Quartz Monzonites; also, San Isabel Granite of Boyer (1962) and unnamed granitic rocks
Granitic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic)
Includes Boulder Creek -M.Y. AGE GROUP (AGE 1650-1730 M.Y.)--Includes Boulder Creek, Cross Creek, Denny Creek, Kroenke, Browns Pass, Powderhorn, Pitts Meadow, Bakers Bridge, and Tenmile Granites, Quartz Monzonites, or Granodiorites;
Green River Fm (Phanerozoic | Cenozoic | Tertiary)
Marlstone, sandstone, and oil shale
Green River Fm--Laney Member (Phanerozoic | Cenozoic | Tertiary)
Claystone, oil shale, and sandstone; in Sand Wash basin
Green River Fm--Lower Part (Phanerozoic | Cenozoic | Tertiary)
Shale, sandstone, marlstone, and limestone in Anvil Points, Garden Gulch, and Douglas Creek Members; in Piceance basin
Green River Fm--Parachute Creek Member (Phanerozoic | Cenozoic | Tertiary)
Parachute Creek Member--Oil shale, marlstone, and siltstone; in Piceance basin
Hermosa Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Arkosic sandstone, conglomerate, shale, and limestone; gypsum and salt in Paradox Member present in salt anticlines near Utah border
Huerfano Fm (Phanerozoic | Cenozoic | Tertiary)
Shale and sandstone. Includes Farisita Conglomerate in northwestern Huerfano County
Iles Fm (Phanerozoic | Mesozoic | Cretaceous)
Sandstone and shale. Trout Creek Sandstone Member at top; coal beds in upper half
Ingleside Fm and Fountain Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian)
Ingleside Fm: Limestone and calcareous sandstone. Fountain Fm: arkosic sandstone and conglomerate
Jelm, Lykins, Lyons, and Satanka Fms (Phanerozoic | Paleozoic Mesozoic | Permian Triassic)
Red siltstone, shale, and sandstone
Kayenta Fm, Wingate Sandstone, and Chinle Fm (Phanerozoic | Mesozoic | Triassic)
Kayenta Fm: red siltstone, shale, and sandstone. Chinle Fm: red siltstone and sandstone
Kirtland Shale and Fruitland Fm (Phanerozoic | Mesozoic | Cretaceous)
Shale, sandstone, and major coal beds
Lance Fm (Phanerozoic | Mesozoic | Cretaceous)
Shale, sandstone, and minor coal beds; Fox Hills equivalent at base
Landslide deposits (Phanerozoic | Cenozoic | Quaternary)
Locally includes talus, rock-glacier, and thick colluvial deposits
Laramie Fm (Phanerozoic | Mesozoic | Cretaceous)
Shale, claystone, sandstone, and major coal beds
Laramie Fm and Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous)
Leadville, Gilman, Dyer, Parting, and Sawatch Fms in west-central and south-central. Leadville Limestone, Ouray Limestone, Elbert Fm, and Ignacio Quartzite in far southwest (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous)
Elbert Fm: shale and sandstone.
Leadville Limestone, Gilman Sandstone, Dyer Dolomite, and Parting Fm (Phanerozoic | Paleozoic | Ordovician Silurian(?) Devonian)
Parting Fm: quartzite and shale.
Lodore Fm (Phanerozoic | Paleozoic | Cambrian)
Sandstone, shale, and conglomerate
Lykins Fm (Phanerozoic | Paleozoic Mesozoic | Permian Triassic)
Red siltstone, shale, and limestone
Lykins Fm and Lyons Sandstone (Phanerozoic | Paleozoic Mesozoic | Permian Triassic)
Lykins Lyons and Fountain Fms (Phanerozoic | Paleozoic Mesozoic | Carboniferous Pennsylvanian Permian(?) Triassic)
Red siltstone, sandstone, and conglomerate
Madison Limestone (Phanerozoic | Paleozoic | Carboniferous Mississippian)
Upper part includes equivalents of Upper Mississippian Doughnut and Humbug Fms (shale, limestone, and sandstone)
Madison Limestone and Lodore Fm (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous)
Mafic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic)
Gabbro and mafic diorite and monzonite
Manitou Limestone and Sawatch Quartzite in Southern Front Range and Wet Mountains. One or more Ordovician Fms (Fremont Limestone, Harding Sandstone, and Manitou Dolomite), Dotsero Fm, Peerless Fm, and Sawatch Quartzite in west-ce (Phanerozoic | Paleozoic | Cambrian Ordovician)
Dotsero Fm: Dolomite, in White River plateau only. Peerless Fm: sandstone and dolomite.
Maroon Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian)
Arkosic sandstone, siltstone, conglomerate, and local limestone
Menefee Fm and Point Lookout Sandstone (Phanerozoic | Mesozoic | Cretaceous)
sandstone, shale, and coal; sandstone
Mesaverde Fm, undivided (Phanerozoic | Mesozoic | Cretaceous)
In northwest and west-central: Major coal beds in lower part; Rollins Sandstone Member at base in Delta, Gunnison, and Pitkin Counties. In southwest: sandstone and shale.
Mesaverde Group or Fm--Lower part (Phanerozoic | Mesozoic | Cretaceous)
Sandstone, shale, and major coal beds
Mesaverde Group or Fm--Upper part (Phanerozoic | Mesozoic | Cretaceous)
In Moffat and Rio Blanco Counties, sandstone, shale, and coal beds above Sego Sandstone. Along Grand Hogback south of Colorado River, sandstone and shale above coal-bearing sequence
Middle Park Fm exclusive of Windy Gap Member (Phanerozoic | Cenozoic | Tertiary)
Arkosic sandstone and conglomerate containing abundant volcanic materials. Arbitrary line between Middle Park and Coalmont Formations is at Continental Divide
Minturn and Belden Fms (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Minturn Fm in west-central and south-central and other units (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Arkosic sandstone, conglomerate, shale, and limestone. Includes Madera Fm and Sharpsdale Fm of Chronic (1958) in Sangre de Cristo Range and Gothic Fm of Langenheim (1952) in Elk Mountains. Other units of Middle Pennsylvanian age.
Moenkopi Fm (Phanerozoic | Mesozoic | Triassic)
Red siltstone, mudstone, sandstone, and local gypsum
Morgan Fm and Round Valley Limestone (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Morgan Fm: limestone, sandstone, and shale. In far northwest.
Morrison and Ralston Creek Fms (Phanerozoic | Mesozoic | Jurassic)
Ralston Creek Fm: Claystone, sandstone, limestone, and gypsum
Morrison Fm (Phanerozoic | Mesozoic | Jurassic)
Variegated claystone, mudstone, sandstone, and local beds of limestone
Morrison Fm and Curtis Fm (Phanerozoic | Mesozoic | Jurassic)
Morrison Fm: Variegated claystone, mudstone, sandstone, and local beds of limestone. Curtis Fm: glauconitic sandstone and limestone
Morrison Fm and Sundance Fm (Phanerozoic | Mesozoic | Jurassic)
Sundance Fm: Sandstone, shale, claystone, and limestone
Morrison Fm and Wanakah Fm (Junction Creek Sandstone Member at or near top; Pony Express Limestone Member at base) (Phanerozoic | Mesozoic | Jurassic)
Wanakah Fm: Sandstone, shale, limestone, and local gypsum
Morrison, Wanakah, and Entrada Fms (Phanerozoic | Mesozoic | Jurassic)
Mount Garfield Fm and Sego Sandstone (Phanerozoic | Mesozoic | Cretaceous)
Sandstone and shale; major coal beds in lower part of Mount Garfield
North Park Fm (Phanerozoic | Cenozoic | Tertiary)
Sandstone, siltstone, and conglomerate; in North Park and Laramie basin
Older eolian deposits (Phanerozoic | Cenozoic | Quaternary)
Includes Loveland Loess
Oligocene sedimentary rocks (Phanerozoic | Cenozoic | Tertiary)
Northwest: includes Duchesne River Fm (sandstone and shale; includes some rocks of Eocene age) and Bishop Conglomerate near Utah border. South-central: includes Florissant Lake Beds (tuffaceous shale and tuff) and Antero Fm (lime
Parting, Fremont, and Harding Fms (Phanerozoic | Paleozoic | Ordovician Silurian(?) Devonian)
Poison Canyon Fm (Phanerozoic | Cenozoic | Tertiary)
Arkosic conglomerate, sandstone, and shale
Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Phanerozoic | Cenozoic | Tertiary)
Includes several named units
Quartzite, conglomerate, and interlayered mica schist (Proterozoic | Paleoproterozoic)
Quartzite, conglomerate, and interlayered mica schist
Raton Fm (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary)
Arkosic sandstone, siltstone, and shale; contains major coal deposits in Raton Basin
Red Creek Quartzite (Archean)
Metaquartzite, amphibolite, and mica schist. Present only in small area at Utah border in Uinta Mountains
Rico and Hermosa Fms (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Arkosic sandstone, conglomerate, shale, and limestone. Includes at base in some areas siltstone and shale of Molas Fm or Larsen Quartzite
Rocks of Pikes Peak Batholith (1000-m.y. age group) (Proterozoic | Mesoproterozoic)
Includes Pikes Peak, Mount Rosa, Windy Point, and Redskin Granites and unnamed rocks
Sangre de Cristo Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian)
Arkosic conglomerate, sandstone, and siltstone
San Jose Fm (Phanerozoic | Cenozoic | Tertiary)
Siltstone, shale, and sandstone
Santa Fe Fm (Phanerozoic | Cenozoic | Tertiary)
Siltstone, sandstone, and conglomerate
Sawatch Quartzite (Phanerozoic | Paleozoic | Cambrian)
Locally includes Peerless Fm
South Park Fm (Phanerozoic | Cenozoic | Tertiary)
Arkosic sandstone and shale, volcaniclastic conglomerate, and andesite flows and breccia
Triassic and Permian rocks (Phanerozoic | Paleozoic Mesozoic | Permian Triassic)
Red siltstone, shale, and sandstone. Includes various combinations of Nugget, Jelm, Popo Agie, Chugwater, Red Peak, Forelle, Satanka, and Goose Egg Fms near Wyoming border
Uinta Mountain Group (Proterozoic | Mesoproterozoic)
Quartzite, conglomerate, and shale
Uncompahgre Fm (Proterozoic | Paleoproterozoic Mesoproterozoic)
Quartzite, slate, and phyllite
Upper part of Dawson Arkose (Phanerozoic | Cenozoic | Tertiary)
Arkosic sandstone, conglomerate, and shale. Includes Green Mountain Conglomerate south of Golden
Upper Permian rocks, undivided (Phanerozoic | Paleozoic | Permian)
Siltstone, dolomite, and sandstone; in southeast
Vermejo Fm and Trinidad Sandstone (Phanerozoic | Mesozoic | Cretaceous)
Shale, sandstone, and major coal beds; sandstone
Wasatch Fm (Phanerozoic | Cenozoic | Tertiary)
Claystone, shale, and sandstone
Wasatch Fm--Cathedral Bluffs Tongue (Phanerozoic | Cenozoic | Tertiary)
Claystone, mudstone, and sandstone; in Sand Wash basin
Wasatch Fm (including Fort Union equivalent at base) and Ohio Creek Fm (Phanerozoic | Cenozoic | Tertiary)
Claystone, mudstone, sandstone, and conglomerate
Wasatch Fm--Niland Tongue (Phanerozoic | Cenozoic | Tertiary)
Mudstone, sandstone, and carbonaceous shale; in Sand Wash basin
Weber Sandstone and Maroon Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian)
White River Fm or Group (Phanerozoic | Cenozoic | Tertiary)
East: Ashy claystone and sandstone. Includes Castle Rock Conglomerate in region southeast of Denver. Northwest: Ashy claystone in North Park
Williams Fork Fm (Phanerozoic | Mesozoic | Cretaceous)
Sandstone, shale, and major coal beds
Wingate Sandstone and Chinle Fm (Phanerozoic | Mesozoic | Triassic)
Connecticut
Allingtown Metavolcanics plus Maltby Lakes Metavolcanics (Middle? Ordovician)
Allingtown Metavolcanics plus Maltby Lakes Metavolcanics - Allingtown Metavolcanics - Green, fine-grained, massive greenstone, composed of epidote, actinolite, albite, and chlorite, commonly with abundant megacrysts of saussurite, interlayered with minor green phyllite, generally containing quartz and sericite. Dark amphibole in western outcrops. Maltby Lakes Metavolcanics - Green to gray-green, fine-grained, massive to well-foliated and layered greenstone, greenschist, and schist; also dark amphibolite to west and southwest.
Basal member [of The Straits Schist] (Silurian)
Basal member [of The Straits Schist] ( = Russell Mountain Formation of Massachusetts) - Distinguished by presence of layers of amphibolite, marble, calc-silicate rock, and quartzite within more uniform schist like that on either side. Minor, unevenly distributed mineralization in W, Bi, Cu, Ni, and other metals.
Beardsley Member [of Harrison (Prospect) Gneiss] (Middle? Ordovician)
Beardsley (hornblendic) Member [of Harrison (Prospect) Gneiss] - Medium- to dark-gray, medium-grained, well-layered and lineated gneiss, composed of plagioclase, quartz, microcline, hornblende, biotite, and epidote. Microcline may occur as megacrysts 1 to 3 cm across. Minor layers of garnetiferous schist and rarely of calc-silicate rock or marble. Pumpkin Ground and Beardsley Members of Harrison Gneiss, formerly considered conformable metavolcanic members, are here recognized as juxtaposed metaplutonic units and are renamed the Beardsley and Pumpkin Ground orthogneisses. Isotopic dating yields crystallization ages of 428+/-2 Ma (Early Silurian) for the Pumpkin Ground and 446+/-2 Ma (Late Ordovician) for the Beardsley. Age of the Beardsley based on analysis of seven zircon and two sphene fractions. The Harrison Gneiss as described by Rodgers (1985) has no stratigraphic significance and cannot be correlated regionally (Sevigny and Hanson, 1993).
Brimfield Schist (Upper? and Middle Ordovician)
Brimfield Schist (includes Hamilton Resevoir Formation) - Gray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across. Minor layers and lenses of hornblende- and pyroxene-bearing gneiss, amphibolite, and calc-silicate rock.
Brimfield Schist (uncertain) (Upper? and Middle Ordovician)
Brimfield Schist (uncertain) (includes Hamilton Resevoir Formation) - Gray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across. Minor layers and lenses of hornblende- and pyroxene-bearing gneiss, amphibolite, and calc-silicate rock.
Brookfield Gneiss (Middle? Ordovician)
Brookfield (dioritic and granodioritic) Gneiss (including Newtown Gneiss of Crowley, 1968) - Dark and light, commonly speckled or banded, medium- to coarse-grained, massive to poorly foliated gneiss, composed of plagioclase, biotite, and hornblende, generally with quartz and K-feldspar, the latter commonly as megacrysts 1 to 3 cm across (also plagioclase megacrysts in darker rocks), locally associated with amphibolite or hornblende schist.
Buttress Dolerite (Middle? Jurassic)
Buttress Dolerite - Dark-gray to greenish-gray (weathers brown or gray), medium- to fine-grained, commonly porphyritic, generally massive with well-developed columnar jointing, grading from basalt near contacts to fine-grained gabbro in the interior, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.
Buttress Dolerite (uncertain) (Middle? Jurassic)
Buttress Dolerite (uncertain)- Dark-gray to greenish-gray (weathers brown or gray), medium- to fine-grained, commonly porphyritic, generally massive with well-developed columnar jointing, grading from basalt near contacts to fine-grained gabbro in the interior, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.
Carringtons Pond Member [of Trap Falls Formation] (Middle or Lower Ordovician)
Carringtons Pond Member [of Trap Falls Formation] - Interlayered medium- to dark-gray, rusty-weathering, medium-grained schist and light-gray, fine- to medium-grained gneiss, composed of quartz, sodic plagioclase, biotite, muscovite, and garnet; schist locally contains sillimanite or kyanite; gneiss locally contains K-feldspar; amphibolite layers common.
Cobble Mountain Formation (Middle Ordovician)
Cobble Mountain Formation - Gray to silver (not rusty), medium- to coarse-grained, generally layered schist and granofels, composed of quartz, oligoclase, muscovite, biotite, and garnet, and locally kyanite and staurolite or sillimanite. Some amphibolite layers.
Collins Hill Formation (Upper? and Middle Ordovician)
Collins Hill Formation ( = Partridge Formation of New Hampshire) - Gray, rusty-weathering, medium- to coarse-grained, poorly layered schist, composed of quartz, oligoclase, muscovite, biotite, and garnet, and commonly staurolite, kyanite, or sillimanite, generally graphitic, interlayered with fine-grained two-mica gneiss, especially to the west, and with calc-silicate and amphibolite layers, also rare quartz-spessartine (coticule) layers.
Collinsville Formation (Middle Ordovician)
Collinsville Formation - Mixture of rock types as described for the two members; in many areas felsic and mafic striped metavolcanic rocks predominate.
Dioritic phase [of Preston Gabbro] (Middle Ordovician or older)
Dioritic phase [of Preston Gabbro] - Medium- to dark-gray, streaked or speckled, medium-grained diorite and quartz diorite, gneissic where sheared near contact, composed of plagioclase, hornblende, and biotite, and locally quartz and relic pyroxene.
East Berlin Formation (Lower Jurassic)
East Berlin Formation - Maroon siltstone, silty and sandy shale, and fine-grained silty sandstone, generally well laminated and commonly well indurated, alternating with dark fissile shale; dolomitic carbonate common in cement, concretions, and thin argillaceous laminae. Local arkose; grades eastward into coarse conglomerate close to eastern border fault. The East Berlin Formation of the Hartford basin contains eight facies: trough cross-bedded sandstones, horizontally stratified sandstones, interbedded sandstones and mudrocks, ripple cross-laminated siltstones, black shales, stratified mudrocks, disrupted shales, and disrupted mudstones. These facies are interpreted as a continental depositional system and are divided into two assemblages. Sandflat/alluvial plain facies assemblage (sandstones and siltstones) is composed of sheet-flood deposits. The lacustrine assemblage (shales and mudrocks) represents a saline lake-playa system (Gierlowski-Kordesch and Rust, 1994).
Gneiss (metavolcanic) member [of Brimfield Schist] (Upper? and Middle Ordovician)
Gneiss (metavolcanic) member [of Brimfield Schist] - Medium-gray, medium-grained, layered gneiss and schist, composed of oligoclase, quartz, and biotite; some gneiss and most schist layers contain garnet and sillimanite; some gneiss layers contain garnet, hornblende or pyroxene or grade into amphibolite or calc-silicate rock. Probably includes metavolcanic rocks.
Gneiss of Highlands massifs (Proterozoic Y; may contain some older rocks)
Gneiss of Highlands massifs, (including Fordham Gneiss) - Mixture of rock types described below, where not separately mapped.
Hebron Gneiss (Silurian and Ordovician)
Hebron Gneiss - Interlayered dark-gray, medium- to coarse-grained schist, composed of andesine, quartz, biotite, and local K-feldspar, and greenish-gray, fine- to medium-grained calc-silicate rock, composed of labradorite, quartz, biotite, actinolite, hornblende, and diopside, and locally scapolite. Local lenses of graphitic two-mica schist.
Hornblende gneiss and amphibolite (Proterozoic Y)
Hornblende gneiss and amphibolite - Dark-gray to mottled, fine- to medium-grained, massive to foliated amphibolite and gneiss, composed of hornblende and plagioclase, also commonly biotite and minor quartz; commonly interlayered with banded felsic gneiss. Locally contains calc-silicate rock or diopsidic calcite marble.
Hornblende gneiss member [of Collinsville Formation] (Middle Ordovician)
Hornblende gneiss member [of Collinsville Formation] - Dark, fine- to medium-grained, well-layered amphibolite and hornblende gneiss, composed of hornblende and plagioclase, commonly with biotite, garnet, or epidote, interlayered with light-gray felsic gneiss and pink quartz-spessartine rock (coticule). Grades into Bristol Gneiss.
Layered gneiss (Proterozoic Y)
Layered gneiss - Gray, medium-grained, well-foliated and generally well layered, light and dark, but locally wispy gneiss, composed of quartz and plagioclase, with microcline locally in the light layers and abundant biotite and common hornblende in the dark layers; garnet or epidote locally. Layers and lenses of calc-silicate rock and amphibolite in some areas.
Lower part [of Maltby Lakes Metavolcanics] (Middle? Ordovician)
Lower part [of Maltby Lakes Metavolcanics] - Gray-green to green, fine-grained, generally well foliated greenschist, greenstone, and schist or phyllite, composed of albite and chlorite, plus quartz and sericite or epidote and actinolite. Mixed metavolcanics and metasedimentary rocks.
Maltby Lakes Metavolcanics (Middle? Ordovician)
Maltby Lakes Metavolcanics - Green to gray-green, fine-grained, massive to well-foliated and layered greenstone, greenschist, and schist; also dark amphibolite to west and southwest.
Mamacoke Formation (Proterozoic Z?)
Mamacoke Formation - Interlayered (but layers locally indistinct) light- to dark-gray, medium-grained gneiss, composed of plagioclase, quartz, and biotite; sillimanite, garnet, hornblende, or microcline in certain layers; in upper part locally contains quartz-sillimanite nodules or thin layers of quartzite, amphibolite, or calc-silicate rock.
Maromas Granite Gneiss (Devonian?)
Maromas Granite Gneiss - Light-gray to buff, medium- to fine-grained granitic gneiss, composed of quartz and microcline with minor plagioclase and biotite. Central body is massive, but outlying strips are foliated and have accessory hornblende or garnet. Massive parts may be young anatectic intrusive rocks; foliated parts may include older felsic metavolcanic rocks belonging to unit Ochv. Pegmatite bodies are common in the vicinity.
Metavolcanic member [of Collins Hill Formation] (Upper? and Middle Ordovician)
Metavolcanic member [of Collins Hill Formation] - Ranges from mafic to felsic, from dark layered amphibolite and hornblende schist, locally with garnet or epidote, to light-gray (in places purplish), laminated gneiss, composed of quartz, oligoclase, and biotite, in which some layers contain garnet (generally manganiferous) and hornblende or cummingtonite.
Middle member [of Bigelow Brook Formation] (Silurian or perhaps Ordovician)
Middle member [of Bigelow Brook Formation] - Greenish-gray, medium-grained calc-silicate rock, composed of plagioclase, quartz, and diopside (locally hornblende and scapolite), interbedded with schist and granofels composed of plagioclase, quartz, biotite, and commonly garnet and sillimanite.
Middletown Formation (Middle Ordovician)
Middletown Formation ( = Ammonoosuc Volcanics of New Hampshire) - Heterogeneously interlayered dark- to light-gray, generally medium grained gneiss and granofels, ranging from quartz-biotite gneiss through felsic amphibole gneiss to amphibolite and characteristically containing anthophyllite or cummingtonite with or without hornblende. Also layers of calc-silicate rock and of biotite gneiss with quartz-sillimanite nodules.
Middletown Formation (Middle Ordovician)
Middletown Formation ( = Ammonoosuc Volcanics of New Hampshire) - Heterogeneously interlayered dark- to light-gray, generally medium grained gneiss and granofels, ranging from quartz-biotite gneiss through felsic amphibole gneiss to amphibolite and characteristically containing anthophyllite or cummingtonite with or without hornblende. Also layers of calc-silicate rock and of biotite gneiss with quartz-sillimanite nodules.
Mount Pisgah Member of Littleton Formation (Devonian)
Mount Pisgah Member of Littleton Formation - Gray, medium-grained, well-layered (locally graded) granofels or micaceous quartzite with some schist, composed of quartz, oligoclase, biotite, garnet, and sillimanite.
New Haven Arkose (Upper Triassic; possibly Lower Jurassic at top)
New Haven Arkose - Red, pink, and gray coarse-grained, locally conglomeratic, poorly sorted and indurated arkose, interbedded with brick-red micaceous, locally shaly siltstone and fine-grained feldspathic clayey sandstone.
New Haven Arkose plus Buttress Dolerite (Upper Triassic; possibly Lower Jurassic at top plus Middle? Jurassic)
New Haven Arkose plus Buttress Dolerite - New Haven Arkose - Red, pink, and gray coarse-grained, locally conglomeratic, poorly sorted and indurated arkose, interbedded with brick-red micaceous, locally shaly siltstone and fine-grained feldspathic clayey sandstone. Buttress Dolerite (Middle? Jurassic) - Dark-gray to greenish-gray (weathers brown or gray), medium- to fine-grained, commonly porphyritic, generally massive with well-developed columnar jointing, grading from basalt near contacts to fine-grained gabbro in the interior, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.
Oronoque Schist (Lower? Ordovician)
Oronoque Schist - Gray to silver, medium- to fine-grained, well-layered to laminated schist and granofels, composed of quartz, oligoclase, or albite, muscovite or sericite, biotite, or chlorite, and in western belt local garnet, staurolite, and kyanite. Small lenses of amphibolite or greenstone.
Plainfield Formation (Proterozoic Z?)
Plainfield Formation - Interlayered light-gray, thin-bedded quartzite, in places with feldspar, mica, graphite, or pyrite, light- to medium-gray gneiss composed of quartz, oligoclase, and biotite (rarely microcline), medium- to dark-gray schist composed of quartz, oligoclase, biotite, sillimanite, and garnet, dark-gray or green gneiss composed of plagioclase, quartz, biotite, and hornblende (commonly with diopside), amphibolite, diopsite-bearing quartzite, and calc-silicate rock. In places contains quartz-sillimanite nodules.
Plainfield Formation plus Potter Hill Granite Gneiss plus Narragansett Pier Granite (Proterozoic Z? and Permian)
Plainfield Formation plus Potter Hill Granite Gneiss plus Narragansett Pier Granite - Plainfield Formation - Interlayered light-gray, thin-bedded quartzite, in places with feldspar, mica, graphite, or pyrite, light- to medium-gray gneiss composed of quartz, oligoclase, and biotite (rarely microcline), medium- to dark-gray schist composed of quartz, oligoclase, biotite, sillimanite, and garnet, dark-gray or green gneiss composed of plagioclase, quartz, biotite, and hornblende (commonly with diopside), amphibolite, diopsite-bearing quartzite, and calc-silicate rock. In places contains quartz-sillimanite nodules. Potter Hill Granite Gneiss - Light-pink to gray, tan-weathering, fine- to medium-grained, rarely porphyritic, well-foliated (not lineated) granitic gneiss, composed of microcline, quartz, oligoclase (or albite), biotite, and magnetite, minor muscovite, and local garnet. Narragansett Pier Granite - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.
Plainfield Formation plus Stony Creek Granite Gneiss plus Narragansett Pier Granite (Proterozoic Z? and Permian)
Plainfield Formation - Interlayered light-gray, thin-bedded quartzite, in places with feldspar, mica, graphite, or pyrite, light- to medium-gray gneiss composed of quartz, oligoclase, and biotite (rarely microcline), medium- to dark-gray schist composed of quartz, oligoclase, biotite, sillimanite, and garnet, dark-grey or green gneiss composed of plagioclase, quartz, biotite, and hornblende (commonly with diopside), amphibolite, diopside-bearing quartzite, and calc-silicate rock. In places contains quartz-sillimanite nodules. Stony Creek Granite Gneiss - Red to pink, unevenly medium to very coarse grained, variably foliated granite or granite gneiss, composed of oligoclase, K-feldspar, and quartz with minor biotite and magnetite, sporatic garnet (in foliated varieties), and local muscovite. Commonly contains granite and pegmatite of Narragansett Pier type (and probably age). In much of area both granites occur as innumerable veins penetrating other units or as larger bodies full of inclusions of those units, which can be mapped through the bodies of granite. Narragansett Pier Granite (Permian) - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.
Portland Arkose (Lower Jurassic)
Portland Arkose - Reddish-brown to maroon micaceous arkose and siltstone and red to black fissile silty shale. Grades eastward into coarse conglomerate (fanglomerate).
Potter Hill Granite Gneiss plus Narragansett Pier Granite (Proterozoic Z? and Permian)
Potter Hill Granite Gneiss plus Narragansett Pier Granite - Potter Hill Granite Gneiss - Light-pink to gray, tan-weathering, fine- to medium-grained, rarely porphyritic, well-foliated (not lineated) granitic gneiss, composed of microcline, quartz, oligoclase (or albite), biotite, and magnetite, minor muscovite, and local garnet. Narragansett Pier Granite (Permian) - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.
Preston Gabbro plus Quinebaug Formation (Middle Ordovician or older)
Preston Gabbro plus Quinebaug Formation - Preston Gabbro - Dark, medium- to coarse-grained, mainly massive gabbro, composed of labradorite, augite, and opaques, generally with hornblende, locally hypersthene, or olivine or both. Quinebaug Formation - Medium- to dark-gray, commonly greenish, medium-grained, well-layered gneiss, composed of hornblende, andesine, biotite, and epidote, commonly with quartz or garnet, interlayered with amphibolite.
Quartzite unit [in Plainfield Formation] plus Stony Creek Granite Gneiss plus Narragansett Pier Granite (Proterozoic Z? and Permian)
Quartzite unit [in Plainfield Formation] plus Stony Creek Granite Gneiss plus Narragansett Pier Granite - Quartzite unit [in Plainfield Formation] - light-gray, glassy, generally thin bedded quartzite, also feldspathic and micaceous quartzite containing quartz-sillimanite nodules. Stony Creek Granite Gneiss - Red to pink, unevenly medium to very coarse grained, variably foliated granite or granite gneiss, composed of oligoclase, K-feldspar, and quartz with minor biotite and magnetite, sporatic garnet (in foliated varieties), and local muscovite. Commonly contains granite and pegmatite of Narragansett Pier type (and probably age). In much of area both granites occur as innumerable veins penetrating other units or as larger bodies full of inclusions of those units, which can be mapped through the bodies of granite. Narragansett Pier Granite (Permian) - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.
Ratlum Mountain Schist (Lower? Ordovician)
Ratlum Mountain Schist - Gray, medium-grained, interlayered schist and granofels, composed of quartz, oligoclase, muscovite (in the schist), biotite, and garnet, also staurolite and kyanite in the schist. Numerous layers and lenses of amphibolite; also some of quartz-spessartine (coticule) and calc-silicate rock.
Ratlum Mountain Schist (Lower Ordovician)
Ratlum Mountain Schist - Gray, medium-grained, interlayered schist and granofels, composed of quartz, oligoclase, muscovite (in the schist), biotite, and garnet, also staurolite and kyanite in the schist. Numerous layers and lenses of amphibolite; also some of quartz-spessartine (coticule) and calc-silicate rock.
Ratlum Mountain Schist plus Amphibolite unit [in Ratlum Mountain Schist] (Lower Ordovician)
Ratlum Mountain Schist plus Amphibolite unit [in Ratlum Mountain Schist] - Ratlum Mountain Schist - Gray, medium-grained, interlayered schist and granofels, composed of quartz, oligoclase, muscovite (in the schist), biotite, and garnet, also staurolite and kyanite in the schist. Numerous layers and lenses of amphibolite; also some of quartz-spessartine (coticule) and calc-silicate rock. Amphibolite unit [in Ratlum Mountain Schist] (Lower? Ordovician) - Black or mottled, generally massive amphibolite and hornblende gneiss, composed of hornblende and andesine, commonly with minor quartz and magnetite, and locally with garnet, biotite, and epidote.
Rowe Schist (Lower Ordovician or Cambrian or both)
Rowe Schist - Light-gray to silvery, fine- to medium-grained, generally poorly layered schist, composed of quartz, muscovite, biotite, oligoclase, and generally garnet, staurolite, and kyanite or sillimanite. Layers of granofels common; also some layers of amphibolite, quartz-spessartine rock (coticule), and calc-silicate rock.
Rusty mica schist and gneiss (Proterozoic Y; may contain some older rocks)
Rusty mica schist and gneiss (equivalent in part to Washington Gneiss of Massachusetts) - Dark-gray, rusty-weathering, well-foliated and well- to poorly layered schist and gneiss composed of quartz, plagioclase, biotite, muscovite, sillimanite, and locally garnet; some layers of feldspathic quartzite and garnetiferous amphibolite.
Scotland Schist (Devonian or Silurian or both)
Scotland Schist - Gray to silvery, locally rusty, fine- to medium-grained schist, composed of quartz, muscovite, biotite, staurolite, and oligoclase, locally with kyanite or sillimanite; interlayered, especially below and to the west, with quartz-oligoclase-biotite schist and granofels and locally with quartzite.
Shelton Member [of Trap Falls Formation] (Middle or Lower Ordovician)
Shelton (white gneiss) Member [of Trap Falls Formation] - White, light-gray, or buff, fine- to medium-grained, generally well foliated granitic gneiss, composed of sodic plagioclase, quartz, microcline, muscovite, and garnet (in tiny almost ubiquitous grains), also commonly minor biotite; generally interlayered with mica schist, biotite gneiss, and calc-silicate rock. Thought to be metavolcanic equivalent of unit Og. Shelton Member of Trap Falls Formation (Rodgers, 1985) is here referred to as Shelton muscovite granite. On the basis of field and laboratory studies, Ansonia, Beardsley, Pumpkin Ground, and Shelton gneisses, previously considered stratigraphic units, are reinterpreted as plutonic. Shelton is a foliated, medium-grained, garnet-bearing muscovite leucogranite with a conspicuous white color and abundant garnets. Age of crystallization determined from U-Pb garnet analysis is 380+/-3 Ma (Middle Devonian). Southeast margin of the Shelton is in contact with the Trap Falls Formation (Sevigny and Hanson, 1993).
Shuttle Meadow Formation (Lower Jurassic)
Shuttle Meadow Formation - Maroon to dark-gray, silty shale, siltstone, and fine-grained silty sandstone, generally well and thinly laminated. In the southern part of the State includes a layer, up to 5 m thick, of blue, commonly sandy, fine-grained limestone or dolomitic limestone, grading laterally into calcareous siltstone. Coarser and more arkosic to east and south, grading into conglomerate near the eastern border fault.
Southbridge Formation (Silurian or Ordovician or both)
Southbridge Formation - Dark- to light-gray, locally rusty, fine- to medium-grained interlayered granofels and schist, composed of quartz, plagioclase, and biotite, with muscovite in schist, and amphibole, calc-silicate minerals, K-feldspar in certain layers; also locally mappable units and thinner layers of calc-silicate rock, amphibolite, and sillimanite-garnet and sillimanite-graphite-pyrrhotite schist.
Stockbridge Marble (Lower Ordovician and Cambrian)
Stockbridge Marble (including Inwood Marble) - White to gray, massive to layered marble, generally dolomitic but containing calcite marble in upper part, locally interlayered with schist or phyllite and with calcareous siltstone or sandstone.
Stony Creek Granite Gneiss plus Narragansett Pier Granite (Proterozoic Z? and Permian)
Stony Creek Granite Gneiss plus Narragansett Pier Granite - Stony Creek Granite Gneiss - Red to pink, unevenly medium to very coarse grained, variably foliated granite or granite gneiss, composed of oligoclase, K-feldspar, and quartz with minor biotite and magnetite, sporatic garnet (in foliated varieties), and local muscovite. Commonly contains granite and pegmatite of Narragansett Pier type (and probably age). In much of area both granites occur as innumerable veins penetrating other units or as larger bodies full of inclusions of those units, which can be mapped through the bodies of granite. Narragansett Pier Granite (Permian) - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.
Sweetheart Mountain Member [of Collinsville Formation] (Middle Ordovician)
Sweetheart Mountain Member [of Collinsville Formation] - Gray and silvery (not rusty), medium- to coarse-grained, poorly layered schist, composed of quartz, oligoclase, biotite, muscovite, and garnet, and in places kyanite or sillimanite. Amphibolite layers common; also layers of quartz-spessartine rock (coticule). In the Bristol quad., CT, Collinsville Formation is revised to include a basal unnamed hornblende gneiss member (was upper part of Stanley's (1964) Bristol Member), a middle unnamed metaquartzite member, and the upper Sweetheart Mountain Member. Bristol Member of Stanley (1964) is raised in rank to Bristol Gneiss in the report area. Collinsville unconformably underlies The Straits Schist. Inferred age is Middle Ordovician (Simpson, 1990).
Taine Mountain and Collinsville Formations undivided (Middle to Lower? Ordovician)
Taine Mountain and Collinsville Formations undivided - see Ot and Oc.
Talcott Basalt (Lower Jurassic)
Talcott Basalt - Greenish-gray to black (weathers bright orange to brown), fine- to medium-grained, grading from basalt near contacts to fine-grained gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass. Pillows in many places; volcanic breccia with fragmentary pillows in others.
Tatnic Hill Formation (Upper? and Middle Ordovician)
Tatnic Hill Formation - Medium- to dark-gray, medium-grained gneiss or schist composed of quartz, andesine, biotite, garnet, and sillimanite, locally kyanite, muscovite, or K-feldspar, interlayered with locally mappable units and thinner layers of rusty-weathering graphitic pyrrhotitic two-mica schist, amphibolite, and calc-silicate rock.
Trap Falls Formation (Middle or Lower Ordovician)
Trap Falls Formation (may be equivalent in part to Golden Hill Schist) - Gray to silvery, partly rusty weathering, medium-grained generally well layered schist, composed of quartz, sodic plagioclase, biotite, muscovite, and garnet, locally with sillimanite or kyanite, interlayered with two-mica gneiss and granulite and with amphibolite.
Trap Falls Formation plus Ordovician? granitic gneiss (Middle or Lower Ordovician)
Trap Falls Formation plus Ordovician? granitic gneiss - Trap Falls Formation (may be equivalent in part to Golden Hill Schist) - Gray to silvery, partly rusty weathering, medium-grained generally well layered schist, composed of quartz, sodic plagioclase, biotite, muscovite, and garnet, locally with sillimanite or kyanite, interlayered with two-mica gneiss and granulite and with amphibolite. Ordovician? granitic gneiss (including local terms Ansonia, Mine Hill, "Tyler Lake," "Siscowit") - White, light-gray, buff, or pink, generally foliated granitic gneiss, composed of sodic plagioclase, quartz, microcline, muscovite, and biotite, and locally garnet or sillimanite. Commonly contains numerous inclusions or layers of mica schist and gneiss.
Unit b [of Stockbridge Marble] (Upper and Middle? Cambrian)
Unit b [of Stockbridge Marble] - White, pink, cream, and light-gray, generally well bedded dolomitic marble interlayered with phyllite and schist and with siltstone, sandstone, or quartzite, commonly dolomitic.
Units e and d [of Stockbridge Marble] (Lower Ordovician)
Units e and d [of Stockbridge Marble] - White to gray massive calcite marble, commonly mottled with dolomite and locally interlayered with dolomite marble and calcareous siltstone and sandstone.
Upper member [of Middletown Formation] (Middle Ordovician)
Upper member [of Middletown Formation] - Light-gray, generally rusty weathering, well-layered gneiss and granofels, composed of oligoclase, quartz, biotite, and amphibole (cummingtonite, anthophyllite, gedrite, or hornblende, or several of these), also garnet and chlorite. Many layers of amphibolite and biotite gneiss throughout.
Upper part [of Maltby Lakes Metavolcanics] (Middle? Ordovician)
Upper part [of Maltby Lakes Metavolcanics] - Green to gray-green, fine-grained, layered and foliated to massive greenstone and greenschist, composed of epidote, albite, actinolite, and chlorite, and locally minor quartz, sericite, garnet, pyrite, or calcite. Mainly metavolcanic.
Upper slice of Canaan Mountain Schist (Cambrian?)
Upper slice of Canaan Mountain Schist - Dark-gray to silvery, generally rusty weathering, medium- to coarse-grained, well-foliated, massive to well-layered schist and schistose gneiss, composed of quartz, plagioclase, biotite, muscovite, and generally garnet and sillimanite; also layers of amphibolite.
Waterford Group and Branford Gneiss (Proterozoic Z?)
Waterford Group (may be equivalent in part to Monson Gneiss) - Interlayered part (but layers locally distinct) of Waterford Group, light to dark, generally medium grained gneiss, composed of plagioclase, quartz, and biotite, with hornblende in some layers and microcline in others. Some layers of amphibolite. Branford Gneiss - Gray to white but rarely pink., medium-grained, well-foliated granitic gneiss, composed of oligoclase, K-feldspar, quartz, biotite, garnet, magnetite, and muscovite.
Waterford Group plus Stony Creek Granite Gneiss plus Narragansett Pier Granite (Proterozoic Z? and Permian)
Waterford Group plus Stony Creek Granite Gneiss plus Narragansett Pier Granite - Waterford Group (may be equivalent in part to Monson Gneiss) - Interlayered part (but layers locally distinct) of Waterford Group, light to dark, generally medium grained gneiss, composed of plagioclase, quartz, and biotite, with hornblende in some layers and microcline in others. Some layers of amphibolite. Stony Creek Granite Gneiss - Red to pink, unevenly medium to very coarse grained, variably foliated granite or granite gneiss, composed of oligoclase, K-feldspar, and quartz with minor biotite and magnetite, sporatic garnet (in foliated varieties), and local muscovite. Commonly contains granite and pegmatite of Narragansett Pier type (and probably age). In much of area both granites occur as innumerable veins penetrating other units or as larger bodies full of inclusions of those units, which can be mapped through the bodies of granite. Narragansett Pier Granite (Permian) - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.
Wepawaug Schist (Devonian or Silurian or both)
Wepawaug Schist - Medium- to dark-gray, medium- to fine-grained, well-layered schist or phyllite and metasiltstone, composed of quartz, muscovite or sericite, plagioclase, biotite, and in appropriate metamorphic zones chlorite, garnet, staurolite, and kyanite. Schist or phyllite generally graphic.
West Rock Dolerite (Lower Jurassic)
West Rock Dolerite - Dark-gray to greenish-gray (weathers bright orange to brown), medium- to fine-grained, grading from basalt near contacts to fine-grained gabbro in the interior, generally massive with well-developed columnar jointing, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.
Delaware
Bryn Mawr Formation (?)
Bryn Mawr Formation - Red and brown quartz sand with silt, clay and fine gravel.
Columbia Formation (Pleistocene)
Columbia Formation - Yellow and reddish brown quartz sand with gravel and little clay
Potomac Formation (Cretaceous)
Potomac Formation - Variegated silts and clays with beds of quartz sand.
Wissahickon Schist (Paleozoic)
Wissahickon Schist - Dense micaceous schist, gneiss and migmatite.
Florida
Alluvium (Pleistocene/Holocene)
Alluvium - Undifferentiated Quaternary Sediments - Much of Florida's surface is covered by a varying thickness of undifferentiated sediments consisting of siliciclastics, organics and freshwater carbonates. Where these sediments exceed 20 feet (6.1 meters) thick, they were mapped as discrete units. In an effort to subdivide the undifferentiated sediments, those sediments occurring in flood plains were mapped as alluvial and flood plain deposits (Qal). Sediments showing surficial expression of beach ridges and dunes were mapped separately (Qbd) as were the sediments composing Trail Ridge (Qtr). Terrace sands were not mapped (refer to Healy [1975] for a discussion of the terraces in Florida). The subdivisions of the Undifferentiated Quaternary Sediments (Qu) are not lithostratigraphic units but are utilized in order to facilitate a better understanding of the State's geology. The siliciclastics are light gray, tan, brown to black, unconsolidated to poorly consolidated, clean to clayey, silty, unfossiliferous, variably organic-bearing sands to blue green to olive green, poorly to moderately consolidated, sandy, silty clays. Gravel is occasionally present in the panhandle. Organics occur as plant debris, roots, disseminated organic matrix and beds of peat. Freshwater carbonates, often referred to as marls in the literature, are scattered over much of the State. In southern Florida, freshwater carbonates are nearly ubiquitous in the Everglades. These sediments are buff colored to tan, unconsolidated to poorly consolidated, fossiliferous carbonate muds. Sand, silt and clay may be present in limited quantities. These carbonates often contain organics. The dominant fossils in the freshwater carbonates are mollusks.
Alum Bluff Group (Miocene)
Alum Bluff Group - West of the Apalachicola River, the Hawthorn Group is replaced by the Alum Bluff Group. The Alum Bluff Group includes the Chipola Formation, Oak Grove Sand, Shoal River Formation, Choctawhatchee Formation and the Jackson Bluff Formation (Huddlestun, 1984; Braunstein et al., 1988). The formations included in this group are generally defined on the basis of their molluscan faunas and stratigraphic position (Schmidt and Clark, 1980). Puri (1953) described sediment facies as they relate to the formations of the Alum Bluff Group These sediments are lithologically distinct as a group, not as individual units. Brooks (1982) mapped much of the Alum Bluff Group as the Shoal River Formation. The Alum Bluff Group crops out or is beneath a thin overburden in the western panhandle from river valleys in Okaloosa County eastward to western Jackson County. The Alum Bluff Group consists of clays, sands and shell beds which may vary from fossiliferous, sandy clays to unfossiliferous sands and clays and occasional carbonate beds (Huddlestun, 1984). Mica is a common constituent and glauconite and phosphate occur sporadically. Induration varies from essentially nonindurated in sands to well indurated in carbonate lenses. Colors range from cream to olive gray with mottled reddish brown in weathered sections. Sand grain size varies from very fine to very coarse with sporadic occurrences of gravel. These sediments generally have low permeabilities and are part of the intermediate confining unit/aquifer system.
Anastasia Formation (Pleistocene)
Anastasia Formation - The Atlantic Coastal Ridge is underlain by the Anastasia Formation from St. Johns County southward to Palm Beach County. Excellent exposures occur in Flagler County in Washington Oaks State Park, in Martin County at the House of Refuge on Hutchinson Island and at Blowing Rocks in Palm Beach County. An impressive exposure of Anastasia Formation sediments occurs along Country Club Road in Palm Beach County (Lovejoy, 1992). The Anastasia Formation generally is recognized near the coast but extends inland as much as 20 miles (32 kilometers) in St. Lucie and Martin Counties. The Anastasia Formation, named by Sellards (1912),is composed of interbedded sands and coquinoid limestones. The most recognized facies of the Anastasia sediments is an orangish brown, unindurated to moderately indurated, coquina of whole and fragmented mollusk shells in a matrix of sand often cemented by sparry calcite. Sands occur as light gray to tan and orangish brown, unconsolidated to moderately indurated, unfossiliferous to very fossiliferous beds. The Anastasia Formation forms part of the surficial aquifer system.
Avon Park Formation (Eocene)
Avon Park Formation - Middle Eocene carbonate sediments of peninsular Florida, as originally described by Applin and Applin (1944), were subdivided, in ascending order, into the Lake City Limestone and the Avon Park Limestone. Miller (1986) recommended combining the Lake City Limestone with the Avon Park Limestone and, due to the common occurrence of dolostone, referred to the unit as the Avon Park Formation. Carbonates of the Avon Park Formation are the oldest sediments exposed in the state. The Avon Park Formation crops out in a limited area in west-central peninsular Florida in Levy and Citrus Counties on the crest of the Ocala Platform. The Avon Park Formation consists of cream to light-brown or tan, poorly indurated to well indurated, variably fossiliferous, limestone (grainstone, packstone and wackestone, with rare mudstone). These limestones are interbedded with tan to brown, very poorly indurated to well indurated, very fine to medium crystalline, fossiliferous (molds and casts), vuggy dolostones. The fossils present include mollusks, foraminifers, echinoids, algae and carbonized plant remains. Molds and casts of gypsum crystals occur locally. The Avon Park Formation is part of the Floridan aquifer system (FAS). Parts of the Avon Park Formation comprise important, subregional confining units within the FAS (Miller, 1986).
Beach ridge and dune (Pleistocene/Holocene)
Beach ridge and dune - Undifferentiated Quaternary Sediments - Much of Florida's surface is covered by a varying thickness of undifferentiated sediments consisting of siliciclastics, organics and freshwater carbonates. Where these sediments exceed 20 feet (6.1 meters) thick, they were mapped as discrete units. In an effort to subdivide the undifferentiated sediments, those sediments occurring in flood plains were mapped as alluvial and flood plain deposits (Qal). Sediments showing surficial expression of beach ridges and dunes were mapped separately (Qbd) as were the sediments composing Trail Ridge (Qtr). Terrace sands were not mapped (refer to Healy [1975] for a discussion of the terraces in Florida). The subdivisions of the Undifferentiated Quaternary Sediments (Qu) are not lithostratigraphic units but are utilized in order to facilitate a better understanding of the State's geology. The siliciclastics are light gray, tan, brown to black, unconsolidated to poorly consolidated, clean to clayey, silty, unfossiliferous, variably organic-bearing sands to blue green to olive green, poorly to moderately consolidated, sandy, silty clays. Gravel is occasionally present in the panhandle. Organics occur as plant debris, roots, disseminated organic matrix and beds of peat. Freshwater carbonates, often referred to as marls in the literature, are scattered over much of the State. In southern Florida, freshwater carbonates are nearly ubiquitous in the Everglades. These sediments are buff colored to tan, unconsolidated to poorly consolidated, fossiliferous carbonate muds. Sand, silt and clay may be present in limited quantities. These carbonates often contain organics. The dominant fossils in the freshwater carbonates are mollusks.
Chattahoochee Formation (Miocene)
Chattahoochee Formation - The Chattahoochee Formation, originally named by Dall and Stanley-Brown (1894), is predominantly a yellowish gray, poorly to moderately indurated, fine-grained, often fossiliferous (molds and casts), silty to finely sandy dolostone (Huddlestun, 1988). Siliciclastic beds and limestones may be present. The Chattahoochee Formation is exposed in Jackson County, central panhandle, on the Chattahoochee "Anticline". It grades laterally across the Gulf Trough into the St. Marks Formation through a broad transition area (Scott, 1986). The Chattahoochee Formation forms the upper part of the FAS in the central panhandle.
Citronelle Formation (Pliocene)
Citronelle Formation - The Citronelle Formation is widespread in the Gulf Coastal Plain. The type section for the Citronelle Formation, named by Matson (1916), is near Citronelle, Alabama. The Citronelle Formation grades laterally, through a broad facies transition, into the Miccosukee Formation of the eastern Florida panhandle. Coe (1979) investigated the Citronelle Formation in portions of the western Florida panhandle. The Citronelle Formation is a siliciclastic, deltaic deposit that is lithologically similar to, and time equivalent with, the Cypresshead Formation and, at least in part, the Long Key Formation (Cunningham et al., 1998) of the peninsula. In the western panhandle, some of the sediments mapped as Citronelle Formation may be reworked Citronelle. The lithologies are the same and there are few fossils present to document a possible younger age. The Citronelle Formation consists of gray to orange, often mottled, unconsolidated to poorly consolidated, very fine to very coarse, poorly sorted, clean to clayey sands. It contains significant amounts of clay, silt and gravel which may occur as beds and lenses and may vary considerably over short distances. Limonite nodules and limonite-cemented beds are common. Marine fossils are rare but fossil pollen, plant remains and occasional vertebrates are found. Much of the Citronelle Formation is highly permeable. It forms the Sand and Gravel Aquifer of the surficial aquifer system.
Hawthorn Group (Miocene)
Hawthorn Group - Undifferentiated Hawthorn Group - The undifferentiated Hawthorn Group occurs at or near the surface near the southern flank of the Ocala Platform from Gilchrist County southward to Pasco County with isolated occurrences in Pinellas County. Correlation of these sediments to the formations of the Hawthorn Group exposed to the east and in the subsurface is uncertain. There is little to no phosphate present in these sediments and fossils are rare. Ages have not been documented but stratigraphic position suggests inclusion in the Hawthorn Group. These sediments may be residual from the weathering and erosion of the Hawthorn Group. The Hawthorn Group sediments on the Brooksville Ridge are deeply weathered and in some outcrops look like Cypresshead Formation siliciclastics. The undifferentiated Hawthorn Group sediments are light olive gray and blue gray in unweathered sections to reddish brown in deeply weathered sections, poorly to moderately consolidated, clayey sands to silty clays and relatively pure clays. These sediments are part of the intermediate confining unit/aquifer system and provide an effective aquitard for the FAS, except where perforated by karst features. Hard-rock phosphate deposits are associated with the undifferentiated Hawthorn Group sediments on the eastern flank of the Brooksville Ridge. The hard rock phosphate deposits were formed by the dissolution of phosphate in the Hawthorn sediments and redeposition in karst features.
Hawthorn Group, Arcadia Formation (Oligocene/Miocene)
Hawthorn Group, Arcadia Formation - The undifferentiated Arcadia Formation and the Tampa Member crop out on the southwestern flank of the Ocala Platform from Pasco County southward to Sarasota County. Although ages of the outcropping sediments have not been accurately determined, stratigraphic position suggests that the Upper Oligocene parts of the Arcadia Formation and Tampa Member are exposed in this region, particularly from Hillsborough County northward to Pasco County. The Arcadia Formation, named by Scott (1988), is predominantly a carbonate unit with a variable siliciclastic component, including thin beds of siliciclastics. Within the outcrop area, the Arcadia Formation, with the exception of the Tampa Member, is composed of yellowish gray to light olive gray to light brown, micro to finely crystalline, variably sandy, clayey, and phosphatic, fossiliferous limestones and dolostones. Thin beds of sand and clay are common. The sands are yellowish gray, very fine to medium grained, poorly to moderately indurated, clayey, dolomitic and phosphatic. The clays are yellowish gray to light olive gray, poorly to moderately indurated, sandy, silty, phosphatic and dolomitic. Molds and casts of mollusks are common in the dolostones. Silicified carbonates and opalized claystone are found in the Arcadia Formation.
Hawthorn Group, Arcadia Formation, Tampa Member (Oligocene/Miocene)
Hawthorn Group, Arcadia Formation, Tampa Member - The Tampa Member consists predominantly of limestone with subordinate dolostone, sand and clay (Scott, 1988). The lithology of the Tampa Member is very similar to that of the subsurface limestone part of the Arcadia Formation except that the Tampa Member contains noticeably less phosphate (Scott, 1988). The limestone in the Tampa is white to yellowish gray, fossiliferous and variably sandy and clayey mudstone, wackestone and packstone with minor to no phosphate grains. Sand and clay beds are like those in the undifferentiated Arcadia Formation. Mollusks and corals are common in the Tampa Member as molds and casts, silicified pseudomorphs and original shell material. The Tampa Member and the lower part of the Arcadia Formation form the upper part of the Floridan aquifer system (FAS) in parts of southern Florida (Miller, 1986; Scott, 1991).
Hawthorn Group, Coosawhatchie Formation (Miocene)
Coosawhatchie Formation - The Coosawhatchie Formation is exposed or lies beneath a thin overburden on the eastern flank of the Ocala Platform from southern Columbia County to southern Marion County. Within the outcrop region, the Coosawhatchie Formation varies from a light gray to olive gray, poorly consolidated, variably clayey and phosphatic sand with few fossils, to an olive gray, poorly to moderately consolidated, slightly sandy, silty clay with few to no fossils. Occasionally the sands will contain a dolomitic component and, rarely, the dominant lithology will be dolostone or limestone. Silicified nodules are often present in the Coosawhatchie Formation sediments in the outcrop region. The sediment may contain 20 percent or more phosphate (Scott, 1988). Permeability of the Coosawhatchie sediments is generally low, forming part of the intermediate confining unit/aquifer system.
Hawthorn Group, Coosawhatchie Formation, Charlton Member (Miocene/Pliocene)
Hawthorne Group, Coosawhatchie Formation, Charlton Member - The Charlton Member (originally the Charlton formation, Veatch and Stevenson, 1911), crops out only in northern Nassau County near and along the St. Marys River. The Charlton Member in this area consists primarily of light gray to greenish gray, poorly to moderately consolidated, dolomitic to calcareous, silty, sandy, locally fossiliferous clays. Few carbonate beds occur.
Hawthorn Group, Peace River Formation (Miocene/Pliocene)
Hawthorne Group, Peace River Formation - The Peace River Formation crops out or is beneath a thin overburden on the southern part of the Ocala Platform extending into the Okeechobee Basin. These sediments were mapped from Hillsborough County southward to Charlotte County. Within this area, the Peace River Formation is composed of interbedded sands, clays and carbonates. The sands are generally light gray to olive gray, poorly consolidated, clayey, variably dolomitic, very fine to medium grained and phosphatic. The clays are yellowish gray to olive gray, poorly to moderately consolidated, sandy, silty, phosphatic and dolomitic. The carbonates are usually dolostone in the outcrop area. The dolostones are light gray to yellowish gray, poorly to well indurated, variably sandy and clayey, and phosphatic. Opaline chert is often found in these sediments. The phosphate content of the Peace River Formation sands is frequently high enough to be economically mined. Fossil mollusks occur as reworked casts, molds, and limited original shell material. Silicified corals and wood, and vertebrate fossils are also present. The Peace River Formation is widespread in southern Florida. It is part of the intermediate confining unit/aquifer system.
Hawthorn Group, Peace River Formation, Bone Valley Member (Miocene/Pliocene)
Hawthorn Group, Peace River Formation, Bone Valley Member - The Bone Valley Member (originally the Bone Valley Formation of Matson and Clapp, 1909), Peace River Formation occurs in a limited area on the southern part of the Ocala Platform in Hillsborough, Polk and Hardee Counties. Throughout its extent, the Bone Valley Member is a clastic unit consisting of sand-sized and larger phosphate grains in a matrix of quartz sand, silt and clay. The lithology is highly variable, ranging from sandy, silty, phosphatic clays and relatively pure clays to clayey, phosphatic sands to sandy, clayey phosphorites (Webb and Crissinger, 1983). In general, consolidation is poor and colors range from white, light brown and yellowish gray to olive gray and blue green. Mollusks are found as reworked, often phosphatized casts. Vertebrate fossils occur in many of the beds within the Bone Valley Member. Shark's teeth are often abundant. Silicified corals and wood are occasionally present as well. The Bone Valley Member is an extremely important, unique phosphate deposit and has provided much of the phosphate production in the United States during the twentieth century. Mining of phosphate in the outcrop area began in 1888 (Cathcart, 1985) and continues to the present.
Hawthorn Group, Statenville Formation (Miocene)
Hawthorn Group, Statenville Formation - The Statenville Formation occurs at or near the surface in a limited area of Hamilton, Columbia and Baker Counties on the northeastern flank of the Ocala Platform. The formation consists of interbedded sands, clays and dolostones with common to very abundant phosphate grains. The sands predominate and are light gray to light olive gray, poorly indurated, phosphatic, fine to coarse grained with scattered gravel and with minor occurrences of fossils. Clays are yellowish gray to olive gray, poorly consolidated, variably sandy and phosphatic, and variably dolomitic. The dolostones, which occur as thin beds, are yellowish gray to light orange, poorly to well indurated, sandy, clayey and phosphatic with scattered mollusk molds and casts. Phosphate occurs in the Statenville Formation in economically important amounts. Silicified fossils and opalized claystones are found in the Statenville Formation. Permeability of these sediments is generally low, forming part of the intermediate confining unit/aquifer system.
Hawthorn Group, Torreya Formation (Miocene)
Hawthorn Group, Torreya Formation - Torreya Formation - The Torreya Formation is exposed or near the surface from western Gadsden County eastward to western-most Hamilton County. It is informally subdivided into a lower carbonate unit and an upper siliciclastic unit (Scott, 1988). The majority of Torreya Formation outcrops expose the siliciclastic part of the unit. The carbonate sediments are white to light olive gray, generally poorly indurated, variably sandy and clayey, fossiliferous (molds and casts) limestone (mudstone and wackestone). The limestones often grade into calcareous-cemented sands. Phosphate is present in the carbonate sediments, particularly in the Sopchoppy Member. The siliciclastics vary from white to light olive gray, unconsolidated to poorly indurated, slightly clayey sands with minor phosphate to light gray to bluish gray, poorly consolidated, variably silty clay (Dogtown Member). The siliciclastics are sporadically fossiliferous. The Torreya Formation overlies the FAS and forms part of the intermediate confining unit/aquifer system.
Holocene sediments (Holocene)
Holocene sediments - the Holocene sediments in Florida occur near the present coastline at elevations generally less than 5 feet (1.5 meters). The sediments include quartz sands, carbonate sands and muds, and organics.
Jackson Bluff Formation (Pliocene)
Jackson Bluff Formation - The Jackson Bluff Formation, named by Vernon and Puri (1964), occurs at or near the surface in a limited area of the panhandle in Leon, Liberty and Wakulla Counties. It has attracted much attention due to its abundant fossil molluscan fauna (Huddlestun, 1984; Schmidt, 1984). In the outcrop area, the Jackson Bluff Formation is described as a sandy, clayey shell bed (Schmidt, 1984). It is composed of tan to orange-brown to gray green, poorly consolidated, fossiliferous, sandy clays to clayey sands. Fossils present include abundant mollusks, corals, foraminifers and occasional vertebrate remains.
Miami Limestone (Pleistocene)
Miami Limestone - The Miami Limestone (formerly the Miami Oolite), named by Sanford (1909), occurs at or near the surface in southeastern peninsular Florida from Palm Beach County to Dade and Monroe Counties. It forms the Atlantic Coastal Ridge and extends beneath the Everglades where it is commonly covered by thin organic and freshwater sediments. The Miami Limestone occurs on the mainland and in the southern Florida Keys from Big Pine Key to the Marquesas Keys. From Big Pine Key to the mainland, the Miami Limestone is replaced by the Key Largo Limestone. To the north, in Palm Beach County, the Miami Limestone grades laterally northward into the Anastasia Formation. The Miami Limestone consists of two facies, an oolitic facies and a bryozoan facies (Hoffmeister et al. [1967]). The oolitic facies consists of white to orangish gray, poorly to moderately indurated, sandy, oolitic limestone (grainstone) with scattered concentrations of fossils. The bryozoan facies consists of white to orangish gray, poorly to well indurated, sandy, fossiliferous limestone (grainstone and packstone). Beds of quartz sand are also present as unindurated sediments and indurated limey sandstones. Fossils present include mollusks, bryozoans, and corals. Molds and casts of fossils are common. The highly porous and permeable Miami Limestone forms much of the Biscayne Aquifer of the surficial aquifer system.
Miccosukee Formation (Pliocene)
Miccosukee Formation - The Miccosukee Formation, named by Hendry and Yon (1967), is a siliciclastic unit with a limited distribution in the eastern panhandle. It occurs in the Tallahassee Hills from central Gadsden County to eastern Madison County, often capping hills. The Miccosukee Formation grades to the west, through a broad facies transition, in central Gadsden County into the Citronelle Formation. The Miccosukee Formation is a prodeltaic deposit. The Miccosukee Formation is composed of grayish orange to grayish red, mottled, poorly to moderately consolidated, interbedded clay, sand and gravel of varying coarseness and admixtures (Hendry and Yon, 1967). The unit is relatively impermeable but is considered a part of the surficial aquifer system (Southeastern Geological Society, 1986).
Residuum on Eocene sediments (Eocene)
Residuum on Eocene sediments - The post-Eocene residuum lying on Eocene sediments in the panhandle consists of reddish brown, sandy clays and clayey sands with inclusions of weathered Eocene limestones. Some of the inclusions are silicified carbonates.
Residuum on Miocene sediments (Miocene)
Residuum on Miocene sediments - The undifferentiated Miocene residuum, mapped on parts of the Chattahoochee "Anticline", characteristically consists of reddish brown, variably sandy clay with inclusions of variably fossiliferous, silicified limestone. The residuum includes Lower to Upper Miocene and younger weathered sediments.
Residuum on Oligocene sediments (Oligocene)
Residuum on Oligocene sediments - The undifferentiated Oligocene residuum, mapped on parts of the Chattahoochee "Anticline", characteristically consists of reddish brown, variably sandy clay with inclusions of variably fossiliferous, silicified limestone (Huddlestun, 1993). The residuum includes Lower and Upper Oligocene weathered sediments (Huddlestun, 1993).
Reworked Cypresshead sediments (Pliocene/Pleistocene)
Reworked Cypresshead sediments - Undifferentiated reworked Cypresshead Formation- This unit is the result of post depositional reworking of the Cypresshead siliciclastics. The sediments are fine to coarse quartz sands with scattered quartz gravel and varying percentages of clay matrix.
Shelly sediments of Plio-Pleistocene age (Pliocene/Pleistocene)
Shelly sediments of Plio-Pleistocene age - Tertiary-Quaternary Fossiliferous Sediments of Southern Florida - Molluskbearing sediments of southern Florida contain some of the most abundant and diverse fossil faunas in the world. The origin of these accumulations of fossil mollusks is imprecisely known (Allmon, 1992). The shell beds have attracted much attention due to the abundance and preservation of the fossils but the biostratigraphy and lithostratigraphy of the units has not been well defined (Scott, 1992). Scott and Wingard (1995) discussed the problems associated with biostratigraphy and lithostratigraphy of the Plio-Pleistocene in southern Florida. These "formations" are biostratigraphic units. The "formations" previously recognized within the latest Tertiary-Quaternary section of southern Florida include the latest Pliocene - early Pleistocene Caloosahatchee Formation, the early Pleistocene Bermont formation (informal) and the late Pleistocene Fort Thompson Formation. This section consists of fossiliferous sands and carbonates. The identification of these units is problematic unless the significant molluscan species are recognized. Often exposures are not extensive enough to facilitate the collection of representative faunal samples to properly discern the biostratigraphic identification of the formation. In an attempt to alleviate the inherent problems in the biostratigraphic recognition of lithostratigraphic units, Scott (1992) suggested grouping the latest Pliocene through late Pleistocene Caloosahatchee, Bermont and Fort Thompson Formations in to a single lithostratigraphic entity, the Okeechobee formation (informal). In mapping the shelly sands and carbonates, a generalized grouping as Tertiary-Quaternary shell units (TQsu) was utilized. This is equivalent to the informal Okeechobee formation. The distribution of the Caloosahatchee and Fort Thompson Formation are shown on previous geologic maps by Cooke (1945), Vernon and Puri (1964) and Brooks (1982). The Nashua Formation occurs within the Pliocene - Pleistocene in northern Florida. However, it crops out or is near the surface is an area too small to be shown on a map of this scale. Lithologically these sediments are complex, varying from unconsolidated, variably calcareous and fossiliferous quartz sands to well indurated, sandy, fossiliferous limestones (both marine and freshwater). Clayey sands and sandy clays are present. These sediments form part of the surficial aquifer system
Tamiami Formation (Pliocene)
Tamiami Formation - The Tamiami Formation (Mansfield, 1939) is a poorly defined lithostratigraphic unit containing a wide range of mixed carbonate-siliciclastic lithologies and associated faunas (Missimer, 1992). It occurs at or near the land surface in Charlotte, Lee, Hendry, Collier and Monroe Counties in the southern peninsula. A number of named and unnamed members are recognized within the Tamiami Formation. These include: the Buckingham Limestone Member; an unnamed tan clay and sand; an oyster (Hyotissa) facies, a sand facies, the Ochopee Limestone Member, the Bonita Springs Marl Member; an unnamed limestone facies; the Golden Gate Reef Member; and the Pinecrest Sand Member (Missimer, 1992). The individual members of the Tamiami Formation were not separately mapped on the geological map. Lithologies of the Tamiami Formation in the mapped area include: 1) light gray to tan, unconsolidated, fine to coarse grained, fossiliferous sand; 2) light gray to green, poorly consolidated, fossiliferous sandy clay to clayey sand; 3) light gray, poorly consolidated, very fine to medium grained, calcareous, fossiliferous sand; 4) white to light gray, poorly consolidated, sandy, fossiliferous limestone; and 5) white to light gray, moderately to well indurated, sandy, fossiliferous limestone. Phosphate is present in virtually all lithologies as limited quantities of sand- to gravel-sized grains. Fossils present in the Tamiami occur as molds, casts and original material. The fossils present include barnacles, mollusks, corals, echinoids, foraminifers and calcareous nannoplankton. The Tamiami Formation has highly permeable to impermeable lithologies that form a complex aquifer. Locally, it is part of the surficial aquifer system. In other areas, it forms a part of the intermediate confining unit/aquifer system.
Trail Ridge sands (Pleistocene)
Trail Ridge Sands - Undifferentiated sediments - Undifferentiated Quaternary Sediments - Much of Florida's surface is covered by a varying thickness of undifferentiated sediments consisting of siliciclastics, organics and freshwater carbonates. Where these sediments exceed 20 feet (6.1 meters) thick, they were mapped as discrete units. In an effort to subdivide the undifferentiated sediments, those sediments occurring in flood plains were mapped as alluvial and flood plain deposits (Qal). Sediments showing surficial expression of beach ridges and dunes were mapped separately (Qbd) as were the sediments composing Trail Ridge (Qtr). Terrace sands were not mapped (refer to Healy [1975] for a discussion of the terraces in Florida). The subdivisions of the Undifferentiated Quaternary Sediments (Qu) are not lithostratigraphic units but are utilized in order to facilitate a better understanding of the State's geology. The siliciclastics are light gray, tan, brown to black, unconsolidated to poorly consolidated, clean to clayey, silty, unfossiliferous, variably organic-bearing sands to blue green to olive green, poorly to moderately consolidated, sandy, silty clays. Gravel is occasionally present in the panhandle. Organics occur as plant debris, roots, disseminated organic matrix and beds of peat. Freshwater carbonates, often referred to as marls in the literature, are scattered over much of the State. In southern Florida, freshwater carbonates are nearly ubiquitous in the Everglades. These sediments are buff colored to tan, unconsolidated to poorly consolidated, fossiliferous carbonate muds. Sand, silt and clay may be present in limited quantities. These carbonates often contain organics. The dominant fossils in the freshwater carbonates are mollusks.
Undifferentiated sediments (Pleistocene/Holocene)
Undifferentiated sediments - Undifferentiated Quaternary Sediments - Much of Florida's surface is covered by a varying thickness of undifferentiated sediments consisting of siliciclastics, organics and freshwater carbonates. Where these sediments exceed 20 feet (6.1 meters) thick, they were mapped as discrete units. In an effort to subdivide the undifferentiated sediments, those sediments occurring in flood plains were mapped as alluvial and flood plain deposits (Qal). Sediments showing surficial expression of beach ridges and dunes were mapped separately (Qbd) as were the sediments composing Trail Ridge (Qtr). Terrace sands were not mapped (refer to Healy [1975] for a discussion of the terraces in Florida). The subdivisions of the Undifferentiated Quaternary Sediments (Qu) are not lithostratigraphic units but are utilized in order to facilitate a better understanding of the State's geology. The siliciclastics are light gray, tan, brown to black, unconsolidated to poorly consolidated, clean to clayey, silty, unfossiliferous, variably organic-bearing sands to blue green to olive green, poorly to moderately consolidated, sandy, silty clays. Gravel is occasionally present in the panhandle. Organics occur as plant debris, roots, disseminated organic matrix and beds of peat. Freshwater carbonates, often referred to as marls in the literature, are scattered over much of the State. In southern Florida, freshwater carbonates are nearly ubiquitous in the Everglades. These sediments are buff colored to tan, unconsolidated to poorly consolidated, fossiliferous carbonate muds. Sand, silt and clay may be present in limited quantities. These carbonates often contain organics. The dominant fossils in the freshwater carbonates are mollusks.
Undifferentiated sediments (Pliocene/Pleistocene)
Undifferentiated sediments - Undifferentiated Tertiary-Quaternary Sediments - These sediments are siliciclastics that are separated from undifferentiated Quaternary sediments solely on the basis of elevation. Based on the suggestion that the Pleistocene sea levels reached a maximum of approximately 100 feet (30 meters) msl (Colquhoun, 1969), these sediments, which occur above 100 feet (30 meters) msl, are predominantly older than Pleistocene but contain some sediments reworked during the Pleistocene. This unit may include fluvial and aeolian deposits. The undifferentiated Tertiary-Quaternary sediments occur in a band extending from the Georgia-Florida state line in Baker and Columbia Counties southward to Alachua County. These sediments are gray to blue green, unconsolidated to poorly consolidated, fine to coarse grained, clean to clayey, unfossiliferous sands, sandy clays and clays. Organic debris and disseminated organics are present in these sediments. The undifferentiated Tertiary-Quaternary sediments are part of the surficial aquifer system.
Georgia
Amphibolite/ Biotitic Gneiss/ Quartz Sericite Schist (Precambrian-Paleozoic)
Amphibolite/ Biotitic Gneiss/ Quartz Sericite Schist
Amphibolite/ Epidote Quartzite/ Granite Gneiss (Precambrian-Paleozoic)
Amphibolite/ Epidote Quartzite/ Granite Gneiss
Amphibolite/ Metagraywacke/ Mica Schist (Precambrian-Paleozoic)
Amphibolite/ Metagraywacke/ Mica Schist
Amphibolite/ Mica Schist/ Biotitic Gneiss (Precambrian-Paleozoic)
Amphibolite/ Mica Schist/ Biotitic Gneiss
Amphibolitic Schist/ Amphibolite-Metagraywacke/ Mica Schist (Precambrian-Paleozoic)
Amphibolitic Schist/ Amphibolite-Metagraywacke/ Mica Schist
Biotite Gneiss/ Hornblende Gneiss/ Granite Gneiss (Age not given)
Biotite Gneiss/ Hornblende Gneiss/ Granite Gneiss
Biotite Granite Gneiss/ Feldspathic Biotite Gneiss/ Amphibolite Hornblende Gneiss (Precambrian-Paleozoic)
Biotite Granite Gneiss/ Feldspathic Biotite Gneiss/ Amphibolite Hornblende Gneiss
Biotitic Gneiss / Mica Schist/ Amphibolite (Precambrian-Paleozoic)
Biotitic Gneiss / Mica Schist/ Amphibolite
Chilhowee Formation (Cambrian)
Chilhowee Formation, includes Weisner Formation of Kesler, 1950
Claiborne undifferentiated (Eocene)
Claiborne undifferentiated, up-dip equivalent of Lisbon and Tallahatta Formations
Clayton Formation (Paleocene)
Clayton Formation
Cusseta Sand (Cretaceous)
Cusseta Sand
Epidote Quartzite/ Amphibolite/ Sericite Schist/ Biotite Granite Gneiss (Precambrian-Paleozoic)
Epidote Quartzite/ Amphibolite/ Sericite Schist/ Biotite Granite Gneiss
"Hawthorn Formation" (Miocene)
"Hawthorn Formation", includes Marks Head Formation; Parachucia Beds (Sloan, 1905); and Alum Bluff Formation (Veatch and Stephenson, 1911).
Hornblende Gneiss/ Amphibolite/ Granite Gneiss (Precambrian-Paleozoic)
Hornblende Gneiss/ Amphibolite/ Granite Gneiss
Hornblende Gneiss/ Granite Gneiss/ Biotite Gneiss (Precambrian-Paleozoic)
Hornblende Gneiss/ Granite Gneiss/ Biotite Gneiss
Lookout Sandstone; Gizzard Formation (Pennsylvanian)
Lookout Sandstone; Gizzard Formation
Meta-argillite/ Sericite phyllite/ Metavolcanics (Precambrian-Paleozoic)
Meta-argillite/ Sericite phyllite/ Metavolcanics
Metagraywacke/ Mica Schist/ Calc-silicate Gneiss (Precambrian-Paleozoic)
Metagraywacke/ Mica Schist/ Calc-silicate Gneiss
Metagraywacke/ Mica Schist-Quartzite/ Amphibolite (Precambrian-Paleozoic)
Metagraywacke/ Mica Schist-Quartzite/ Amphibolite
Mica Schist/ Gneiss/ Amphibolite (Precambrian-Paleozoic)
Mica Schist/ Gneiss/ Amphibolite
Mica Schist/ Quartzite/ Gneiss/ Amphibolite (Precambrian-Paleozoic)
Mica Schist/ Quartzite/ Gneiss/ Amphibolite
Miccosukee Formation (Neogene)
Miccosukee Formation
Mississippian undifferentiated (Mississippian)
Mississippian undifferentiated: Includes Pennington Shale, Bangor Limestone (except in Floyd County), Hartselle Sandstone, Golconda Formation, Gasper Limestone, Ste. Genevieve Limestone and St. Louis Limestone
Pennsylvanian undifferentiated (Pennsylvanian)
Pennsylvanian undifferentiated
Phyllite/ Quartzite/ Calc-silicate gneiss (Precambrian-Paleozoic)
Phyllite/ Quartzite/ Calc-silicate gneiss
Quartzite/ Mica Schist/ Amphibolite (Precambrian-Paleozoic)
Quartzite/ Mica Schist/ Amphibolite
Quartz Mica Schist/ Hornblende Schist/ Biotitic Gneiss (Precambrian-Paleozoic)
Quartz Mica Schist/ Hornblende Schist/ Biotitic Gneiss
Ripley Formation (Cretaceous)
Ripley Formation
Sericite Schist/ Amphibolite/ Granite gneiss (Precambrian-Paleozoic)
Sericite Schist/ Amphibolite/ Granite gneiss
Sericite Schist/ Micaceous Quartzite/ Sericite Phyllite (Precambrian-Paleozoic)
Sericite Schist/ Micaceous Quartzite/ Sericite Phyllite
Sillimanite Schist/ Gneiss/ Amphibolite (Precambrian-Paleozoic)
Sillimanite Schist/ Gneiss/ Amphibolite
Slate/ Quartzite/ Conglomerate (Precambrian-Paleozoic)
Slate/ Quartzite/ Conglomerate
Tallahatta Formation (Eocene)
Tallahatta Formation
Tuscaloosa Formation (Cretaceous)
Tuscaloosa Formation
Undifferentiated Metavolcanics/ Sericite phyllite/ Meta-argillite/ Quartz mica schist (Precambrian-Paleozoic)
Undifferentiated Metavolcanics/ Sericite phyllite/ Meta-argillite/ Quartz mica schist
Undifferentiated pelitic rocks (Precambrian-Paleozoic)
Undifferentiated pelitic rocks, includes mica schists, metasiltstones, metaconglomerates, and metagraywackes
Iowa
Cherokee Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Des Moines])
Cyclic deposits with carbonaceous shale, clay, siltstone, with lesser sandstone, and thick coal beds; minor but persistent limestone beds; may include parts of Atoka or Morrow Series.
Colorado and Dakota Groups (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late)
Sandstone and shale with minor limestone; includes Carlile, Greenhorn, Graneros, and Dakota FMs. Full section present in only the extreme NW part of Iowa; in southern and easternmost areas only Dakota is present.
Cretaceous Undifferentiated (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late)
Variably calcareous, serverely deformed shales, minor sandstone and carbonate rock; in Manson anomalous area only
Douglas Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Virgil])
Cyclic deposits with shale, siltstone and minor thin limestone beds; Lawrence Formation at top and Stranger Formation at base.
Ft. Dodge Beds (Phanerozoic | Mesozoic | Jurassic)
Gypsum and red and green shale; in Webster CO only
Galena-Decorah-Platteville Formations (Phanerozoic | Paleozoic | Ordovician-Middle [Mohawkian])
Galena FM- dolomite, minor limestone; chert in lower half. Approx thickness 230 ft. Decorah FM- brown limestone and dolomite; gray-green and brown shales at top and base. Approx thickness 60 ft. Platteville FM- fossiliferous gray limestone and brown dolomite; grayish-green shale at base (Glenwood). Fine- to medium-grained sandstone occurs above the Glenwood in the subsurface of southeastern Iowa. Approx thickness 110 ft
Kinderhook Series (Phanerozoic | Paleozoic | Carboniferous Mississippian-Early)
Gilmore City Limestone- light gray fossiliferous limestone, commonly oolitic. Approx thickness 155 ft. Hampton Formation- limestone and dolomite; fossiliferous gray chert in lower portion. Approx. thickness 150 ft. Starrs Cave Formation- bio-fragmental limestone; oolitic in part. Approx thickness 15 ft. Prospect Hill Formation- greenish-gray siltstone. Approx thickness 90 ft. McCraney Limestone- very pale orange to pale yellowish-brown sublithographic limestone and brown dolomite. Approx thickness 65 ft.
LaPort City Chert (Phanerozoic | Paleozoic | Devonian-Early)
Predominantly chert with limestone and dolomite; minor shale and sandstone. Found in subsurface only.
Lime Creek Formation (Phanerozoic | Paleozoic | Devonian-Late)
Fossiliferous limestone or dolomite in upper part with local stromatoporoid biostromes in north-central Iowa; extremely fossiliferous gray shale and argillaceous limestone in middle; gray shale in lower part with spore carps toward base.
Maquoketa Formation (Phanerozoic | Paleozoic | Ordovician-Late [Cincinnatian])
Predominantly grayish-green shale in east-central area; predominantly brown dolomite and chert in the subsurface of north-central and western areas; red shale with limonite or hematite pellets (Neda) occurs locally at top.
Marmaton Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Des Moines])
Alternating shale and limestone, with some sandstone and coal; Lenapah FM at top and Fort Scott at base.
Meramec Series (Phanerozoic | Paleozoic | Carboniferous Mississippian-Late)
Ste. Genevieve Limestone- fossiliferous limestone and red and green shale. Approx. thickness 50 ft. St. Louis Limestone- limestone and dolomite, sandstone locally perdominant; locally contains chert. Spergen Formation- sandy micaceous dolomite.
Osage Series (Phanerozoic | Paleozoic | Carboniferous Mississippian-Early)
Warsaw Formation- gray, dolomitic shale and argillaceous dolomite; chalcedonic chert. Locally contains many geodes.Approx thickness 85 ft. Keokuk Limestone- fossiliferous, gray or brown limestone and dolomite; gray and brown chert with white spicules, locally predominant in lower portion; minor brown or gray shale. Approx thickness 90 ft. Burlington Limestone- gray, fossiliferous limestone and darker gray dolomite; white and gray mottled fossiliferous chert, locally contains dolomite crystals; two widespread glauconite zones; basal sandstone locally in southeastern Iowa. Approx thickness 80 ft.
Pleasanton Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Missouri])
Shale with some sandstone, thin limestone beds and minor coal; Exline Limestone near top Chariton Conglomerate at base. .
Prairie du Chien Formation (Phanerozoic | Paleozoic | Ordovician-Early [Beekmantown])
Sandy dolomite in upper postion; sandstone in middle portion; dolomite with oolitic and tripolitic chert in lower portion.
Shell Rock Formation (Phanerozoic | Paleozoic | Devonian-Late)
Predominantly stromatoporoid biostromes in upper part; argillaceous limestone and gray shale in middle; massive limestone and dolomite in lower part with stromatoporoid biostromes near base; in north-central Iowa only.
St. Croixan Series (Phanerozoic | Paleozoic | Cambrian-Furongian)
Jordan Sandstone- fine- to medium-grained, well sorted, frosted sandstone (includes Madison Sandstone). Approx thickness 120 ft. St. Lawrence Formation- coarsely crystalline, gray, silty dolomite; glauconite common (includes Lodi Sandstone).Approx thickness 230+ ft Franconia Sandstone- glauconitic, dolomitic siltstone and shale and glauconitic sandstone. Approx thickness 280 ft Galesville Sandstone- medium- to coarse-grained, white to gray sandstone. Eau Claire Sandstone- fissile, gray, silty shale and dolomitic siltstone and fine-grained sandstone. Mt. Simon Sandstone- medium- to coarse-grained sandstone with minor shale stringers. Galesville+Eau Claire+Mt. Simon=Approx thickness 1000 ft
Wabaunsee Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Virgil])
Cyclic deposits, principally shale with limestone, siltstone, minor sandstone units and thin coal seams.
Wapsipinicon Formation (Phanerozoic | Paleozoic | Devonian-Middle)
In descending order, finely crystalline limestone; brown dolomite with gypsum; gray, sandy shale and argillcceous limestone; and massive, finely crystalline, dolomitic limestone and pale-orange dolomite.
Yellow Spring Group (Phanerozoic | Paleozoic | Devonian-Late)
English River Formation- gray siltstone; southeastern Iowa; locally in north-central Iowa. Approx thickness 23 ft. Maple Mill Shale- greenish-gray shale, silty in upper part; contains spore carps; discoidal, concentrically laminated limonite pellets at top in the subsurface of central and southwestern Iowa. Approx thickness 300 ft. Aplington Formation- argillaceous, silty dolomite and minor chert; quartz geodes. Approx thickness 40 ft. Sheffield Formation- greenish-gray shale in central Iowa and in the subsurface of southwestern Iowa; in decending order, dusky yellowish-brown shale followed by greenish-gray shale, very light olive-gray shale, and dark olive-gray shale in the subsurface of southeastern Iowa. Approx thickness 95 ft.
Idaho
Amphibolite after gabbro, diabase, and diorite; Middle Proterozoic sill-like intrusions; southern and northern Belt provinces (Middle Proterozoic)
Younger or Intermediate Precambrian age intrusive rock undifferentiated; Intrusive rock of eastern Idaho; appears older than Cretaceous, possibly Precambrian; Highly metamorphosed rock of central Idaho; age and origin of rock questionable.
Arenite, carbonate, conglomerate, and shale; Late Proterozoic rifted continental margin; southeastern Idaho (Late Proterozoic)
Uppermost Younger Precambrian massive quartzite with carbonate beds of central and southeastern Idaho; overlies (Z1s).
Arenite, dolostone, limestone, siltstone, and shale; Cambrian marine outer continental-shelf deposits; central Idaho (Cambrian)
Cambrian thrusted quartzite, fine-grained detritus, and dolomite of central Idaho.
Arenite, shale, dolostone, siltstone, conglomerate, chert, and limestone; Lower Ordovician marine outer continental-shelf deposits; central Idaho (Early Ordovician)
Lower Ordovician dolomite, nodular cherty limestone, and intraformational conglomerate.
Argillite, quartzite, and calc-silicate rock; Middle Proterozoic Yellowjacket Formation; southern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, dark-colored, feldspathic quartzite with minor limestone beds of southern Idaho.
Argillite, siltite, and quartzite; Middle Proterozoic Ravalli Group; northern Belt Province (Middle Proterozoic)
Intermediate Precambrian sediments, multicolored siltite and argillite overlying quartzite and siltite of northern Idaho.
Argillite, siltite, quartzite, carbonate; Middle Proterozoic Belt metasedimentary rocks (subunits are Y1s, Y2s, Y3s, and Y4s); southern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, northern and southern Idaho; northern Idaho subdivisions are (Y4n, Y3n, Y2n, Y1n) and southern Idaho subdivisions are (Y4s, Y3s, Y2s, Y1s).
Argillite, siltstone, quartzite, and dolostone; Middle Proterozoic Missoula Group; northern Belt province (Middle Middle Proterozoic)
Intermediate Precambrian sediments, light-colored siltite overlying multicolored fine-grained detrital beds of northern Idaho.
Basalt, andesite, diorite, lamprophyre intrusions; Tertiary to Cretaceous, undivided; northern Idaho, central Idaho (Cretaceous or Eocene)
Eocene intrusions including large granitic plutons and dike swarms of central Idaho
Basalt and gravel; Late Pleistocene basalt flows and interlayered gravel of subunit 2b; Snake River Plain (Late Pleistocene)
Upper Pleistocene Snake Plain basaltic lava flows, unit 2.
Basalt and silt; Late Pleistocene basalt flows and interlayered lacustrine silt beds of subunit 1b; Snake River Plain (Late Pleistocene)
Upper Pleistocene Snake Plain basaltic lava flows, unit 1.
Basalt, clay, and gravel; Late Pleistocene basalt flows with interlayered alluvial and lacustrine sediments; Snake River Plain and vicinity (subunits are Qpu1b, Qpu2b, Qpu3b, and Qpu4b) (Late Pleistocene)
Upper Pleistocene Snake Plain lava flows; local stratigraphic position shown by (Qpu4b, Qpu3b, Qpu2b, Qpu1b).
Basalt, clay, and pumice; Late Pleistocene basalt flows, volcaniclastic debris, and ponded sediments of subunit 4b; Snake River Plain; (Late Pleistocene)
Upper Pleistocene Snake Plain basaltic lava flows, unit 4.
Basalt flows and incidental andesite, and latite flows; Miocene mafic to intermediate volcanics; subunits are Tmib, Tm1b, Tm2b, Tm3b; Columbia Plateau, Owyhee Plateau (Miocene)
Miocene plateau basalt flows of western Idaho; subdivisions are (Tm3b, Tm2b, Tm1b).
Basalt flows, basaltic pyroclastic and clastic debris; Middle Pleistocene canyon-filling and plateau lava flows, pyroclastic debris, alluvium, and colluvium; Snake River Plain (Middle Pleistocene)
Middle Pleistocene plateau and canyon-filling basalt in and near Snake Plain.
Basalt flows, pumice, and tuff; Early Pleistocene to Pliocene basaltic volcanics; Snake River Plain (Early Pleistocene)
Lower Pleistocene to Pliocene basalts with associated tuffs and volcanic detritus.
Basalt flows, pyroclastic debris, clastic sediments, and diatomite; Pliocene basaltic volcanics and clastic sediments; Snake River Plain and vicinity (Pliocene)
Pliocene olivine basalt flows and associated tuff and detritus of southern Idaho.
Basalt, gravel, and pumice; Late Pleistocene basaltic volcanics and interlayered sedimetnsof subunit 3b; Snake River Plain (Late Pleistocene)
Upper Pleistocene Snake Plain basaltic lava flows, unit 3.
Basalt, pumice; Holocene basaltic lava flows and cinder cones; Snake River Plain and vicinity (Holocene)
Recent, relatively unweathered Snake Plain basalt flows and cinder cones.
Biotite schist, hornfels, amphibolite, and mylonite; Middle Proterozoic rocks of the Prichard Formation, metamorphosed near the Cretaceous Kaniksu batholith; northern Belt province (Eocene to Middle Proterozoic)
Intermediate Precambrian age metasediments; generally low-to-medium grade; argillite, siltite and minor quartzite of northern Idaho.
Black argillite, quartzite, siltite, marble, chert, and syngenetic silver-lead-zinc deposits; Devonian euxinic marine-basin deposits; central Idaho (Devonian)
Devonian thrusted, deep-water siliceous argillite and quartzite of central Idaho.
Chert, shale, phosphorite, and carbonates; Permian restricted marine epicontinental-basin deposits; southeastern Idaho (Permian)
Permian phosphatic sandstone, mudstone and chert of east-central Idaho.
Clastic debris; Quaternary colluvium, fanglomerate, talus, and glacial deposits; upland-valley margins (Quaternary)
Quaternary colluvium, fanglomerate, and talus plus some glacial debris in upland valleys.
Clay, silt, and minor sand; Late Pleistocene distal glacial-flood deposits; western Snake River Plain (Late Pleistocene)
Pleistocene waterlaid detritus; may be distal deposits of glacial floods and outwash.
Clay, silt, sand, and gravel; Late Pleistocene glacial-lake sediments; Basin and Range province (Late Pleistocene)
Pleistocene glacial-lake, ponded-water, and shoreline sediments.
Conglomerate, sandstone, and siltstone; Eocene to Late Cretaceous alluvial-fan deposits; east-central Idaho, Cordilleran fold-thrust belt, piggyback basins (Eocene to Late Cretaceous )
Lower Tertiary to Upper Mesozoic breccia, conglomerate and sandstone; syntectonic in part.
Coralline Limestone, sandstone, siltstone, shale, chert, and phosphorite; Mississippianshallow marine inner continental-shelf deposits; east-central Idaho, central Idaho (Mississippian )
Mississippian shallow-water coralline limestone interval of southern Idaho.
Dacite to rhyolite (or rhodacite) ignimbrites; Eocene rhyodacitic cauldron complex; east-central Idaho, central Challis volcanic field (Eocene)
Eocene mixed silicic and basaltic volcanic ejecta, flows and reworked debris.
Diorite, gabbro, and granite; Jurassic to Triassic plutons; western Idaho, Blue Mountains island-arc complex (Jurassic to Triassic)
Lower Mesozoic intrusions; localized near the Snake Canyon of western Idaho.
Dolostone, arenite, conglomerate, and chert; Silurian to Middle Ordovician marine outer continental-shelf deposits; east-central Idaho (Silurian to Middle Ordovician)
Silurian to Middle Ordovician marine carbonate-to-clastic strata of east-central Idaho.
Dolostone, limestone, arenite, and chert: Devonian to Ordovician marine outer continental-shelf deposits; east-central Idaho (Devonian to Ordovician)
Devonian to Ordovician marine calcareous sediments north of the Snake Plain.
Dolostone, limestone, arenite, chert, and conglomerate; Ordovician marine continental-shelf deposits; southeastern Idaho (Ordovician)
Ordovician marine dolomite, quartzite, and limestone; subdivisions are (Ou and Ol).
Dolostone, limestone, sandstone, shale, and conglomerate; Devonian marine continental-shelf deposits; east-central and southeastern Idaho (Devonian)
Devonian bedded dolomite and limestone interval of eastern and southern Idaho.
Dolostone, limestone, siltstone, arenite, and chert; Devonian and Silurian marine upper continental-slope deposits; east-central and central Idaho; (Devonian and Silurian)
Devonian and Silurian shallow-water marine carbonate units of east-central Idaho.
Dolostone, quartzite, shale, and limestone; Upper to Middle Ordovician marine continental-shelf deposits; east central Idaho (Late and Middle Ordovician)
Upper and Middle Ordovician dolomite and quartzite unconformably overlying (Ol).
Dolostone, shale, and chert; Silurian marine inner continental-shelf deposits (Late and Middle Silurian)
Upper and Middle Silurian fossiliferous dolomite; clay, silt and sand near base.
Dolostone, shale, arenite, siltstone, limestone, conglomerate, and chert; Ordovician and Cambrian marine outer continental-shelf deposits; central Idaho (Ordovician and Cambrian)
Ordovician and Cambrian thrusted dolomite, siltstone, and quartzite of central Idaho.
Felsic augen gneiss after porphyritic granite; Middle Proterozoic; southern Belt province (Middle Proterozoic)
Augen gneiss, amphibolite and other metamorphosed igneous rocks; possibly Precambrian.
Felsic gneiss, mafic gneiss, orthogneiss, and calc-silicate rock; Early Proterozoic metamorphic rocks; central Idaho; Pioneer Mountains metamorphic core complex (Early Proterozoic)
Precambrian, high-grade metamorphic rock; metasediment subdivisions are (PC3, PC2, PC1).
Gabbro, diorite, amphibolite, lamprophyre; Tertiary to Late Proterozoic, undivided; northern Idaho (Tertiary to Late Proterozoic)
Younger Precambrian dioritic and amphibolitic sills of northern Idaho.
Gabbro, diorite, quartz diorite, aplite; Late to Middle Proterozoic sills injected into sedimentary strata of the Belt Basin; northern Belt province (Late to Middle Proterozoic)
Younger Precambrian dioritic and amphibolitic sills of northern Idaho; basaltic or mafic; as gabbro.
Garnet-mica schist, gneiss, and quartzite; Proterozoic high-grade metasedimentary rocks; trans-Idaho metamorphic province (Late to Early Proterozoic)
Precambrian high-grade metamorphic rock; metasediment; Kyanite-sillimanite-garnet-mica schist and gneiss; minor quartzite
Garnet-sillimanite-biotite gneiss, quartzite, and amphibolite; Middle Proterozoic Lemhi Group; southern Belt trans-Idaho metamorphic provinces (Middle Proterozoic)
Precambrian high-grade metamorphic rock; metasediment; kyanite-sillimanite-garnet-mica coarse-grained schist and gneiss; minor quartzite
Garnet-sillimanite-biotite schist; Middle Proterozoic Prichard Formation, northern Belt province (Early Middle Proterozoic)
Precambrian high-grade metamorphic rock; metasediment; kyanite-sillimanite-garnet-mica coarse-grained schist and gneiss; minor quartzite
Glacial debris; Late Pleistocene glacial till, outwash, and alluvium of continental glaciers; northern Idaho (Late Pleistocene )
Pleistocene till, moraines and similar unsorted glacial debris.
Glacial debris; Late Pleistocene till, outwash, and alluvium of valley glaciers; high mountain valleys (Late Pleistocene )
Pleistocene upland valley deposits; commonly derived from alpine glaciation.
Granitoid intrusions, metasedimentary rocks, and migmatite, undivided; Cretaceous intrusions and Proterozoic host rocks, undivided; northern and central Idaho (Cretaceous to Early Proterozoic)
Mixed, highly altered and migmatitic rocks; derived from imbrication and dynamic events
Granodiorite, quartz monzonite, granite, alaskite, quartz monzodioirte, diorite; Tertiary to Cretaceous, intrusions, undivided; northern, west-central, and southwestern Idaho (Eocene to Cretaceous)
Eocene intrusions; Cretaceous plutons, intermediate, Cretaceous plutons, felsic; metamorphosed granitic intrusive rock
Gravel and sand; Middle Pleistocene alluvial pediment gravel (Pleistocene )
Middle Pleistocene deposits; outwash, fanglomerate, flood and terrace gravels.
Gravel; Early Pleistocene alluvium; western Snake River Plain (Pleistocene)
Lower Pleistocene deposits; outwash, fanglomerate, flood and terrace gravels.
Gravel, sand, and clay; Quaternary-Tertiary colluvium and fanglomerate; western Idaho (Pleistocene and Pliocene)
Pleistocene and Pliocene fanglomerate, colluvium, and poorly sorted gravel deposits.
Gravel, sand, and silt; glacial outburst flood deposits, outwash, fanglomerate, and alluvium, undivided; Pleistocene (Pleistocene)
Pleistocene outwash, fanglomerate, flood and terrace gravels; sudivisions are: (Qpug, Qpmg, and Qplg).
Gravel, sand, and silt; Quaternary; alluvium (Quaternary)
Quaternary alluvium; may contain some glacial deposits and colluvium in uplands
Gravel, sand, and silt; Quaternary basin-filling alluvium; Snake River Plain, Basin and Range provinces (Quaternary)
Quaternary detritus; generally basin-filling deposits of central and southern Idaho.
Gravel, sand, silt, clay; Late Pleistocene glacio-alluvial and lacustrine deposits; Basin and Range, and Snake River Plain (Late Pleistocene)
Upper Pleistocene deposits; outwash, fanglomerate, flood and terrace gravels.
High-grade metasedimentary biotite schist, biotite gneiss, and calc-silicate gneiss; Middle Proterozoic northern Belt province near Idaho batholith (Middle Proterozoic)
Precambrian high-grade metamorphic rock; kyanite-sillimanite calc-silcate bearing schist and gneiss; scapolite common
Intermediate intrusions; mostly Late Cretaceous dioritic to granodioritic plutons of the Idaho batholithic assemblage (Cretaceous)
Cretaceous plutons; intermediate; as granodiorite or diorite; probably includes unmapped older and younger crystalline bodies.
Intrusive andesite, basalt, and diorite; Quaternary to Pliocene subvolcanic intrusions; southeastern Idaho (Quaternary to Pliocene)
Intrusive rocks: mostly Late Cretaceous granodioritic to granitic plutons of the Idaho batholithic assemblage, but including some Eocene intrusions; northern Idaho and Atlanta batholith (Cretaceous to Eocene)
Cretaceous plutons; probably includes unmapped older and younger crystalline bodies.
Limestone, arenite, and shale; Cambrian marine continental-shelf deposits; northern Idaho (Middle Cambrian)
Middle Cambrian thinly laminated claystone overlying coarse-grained pebbly quartzite of northern Idaho.
Limestone, arenite, dolostone, chert, siltstone, shale; Upper Paleozoic marine continental-shelf deposits; southeastern Idaho (Late Paleozoic)
Upper Paleozoic marine sediments in southern Idaho.
Limestone, arenite, shale, dolostone, and siltstone; Upper Proterozoic to Cambrian marine continental-shelf deposits; southeastern Idaho (Cambrian)
Cambrian marine dolomite, limestone, claystone, and quartzite; grades into Precambrian.
Limestone, dolostone, arenite, shale, and siltstone; Lower Paleozoic marine continental-shelf deposits; southeastern Idaho; (Early Paleozoic)
Lower Paleozoic marine carbonate and clastic units southeast of the Snake Plain.
Limestone, dolostone, sandstone, siltstone, and chert; Lower Permian to Lower Pennsylvanian marine continental-shelf deposits; east-central Idaho (Early Permian to Early Pennsylvanian)
Lower Permian to Lower Pennsylvanian (Carboniferous) shallow-water detritus.
Limestone, dolostone, shale, and arenite; Ordovician and Cambrian shallow marine inner continental-shelf deposits; southeastern Idaho (Ordovician and Cambrian)
Ordovician, commonly Lower, and Cambrian marine sediments of eastern and southern Idaho.
Limestone, sandstone, dolostone, and chert; Permian to Pennsylvanian marine epicontinental-basin deposits; southeastern Idaho; (Early Permian to Early Pennsylvanian)
Lower Permian to Lower Pennsylvanian chert, limestone, and sandstone of southern Idaho; subdivisions are (Ps, and PNs).
Limestone, sandstone, shale, and chert; Pennsylvanian marine epicontinental-basin deposits; southeastern Idaho (Pennsylvanian)
Pennsylvanian beds; lowermost portion of the southern Idaho sequence (PPNs).
Limestone, shale, siltstone, chert, and conglomerate; Mississippian western turbiditic flysch to eastern shallow-water carbonates; east-central Idaho (Mississippian)
Mississippian shallow-water carbonate-to-clastic sequence of east-central Idaho.
Limestone, slate; Upper Triassic greenschist-facies metamorphic rocks; western Idaho, Blue Mountains island-arc complex; (Late Triassic)
Upper Triassic shale overlying reefal limestone and dolomite in west-central Idaho.
Meta-conglomerate mafic metavolcanic rocks, siltite, argillite, and limestone; Late Proterozoic rifted continental margin; northwestern Idaho (Late Proterozoic)
Younger Precambrian mafic volcanic flows and conglomerates of northern Idaho.
Metamorphosed granitoid plutonic rocks and metasedimentary rocks, undivided; Cretaceous orthogneiss in Middle Proterozoic metasedimentary host rocks; west-central Idaho (Cretaceous to Middle Proterozoic)
Highly metamorphosed rock of central Idaho; age and origin of rock questionable.
Metamorphosed granodiorite, quartz monzonitek tonalite, quartz diorite; mostly Cretaceous orthogneiss and migmatite; northern and Atlanta batholith; margins of Bitterroot and Atlanta batholiths (Cretaceous)
Metamorphosed granitic intrusive rock; associated with pluton margins and stress areas.
Metasedimentary and meta-igneous rocks; Triassic to Mississippian greenschist-facies dismembered ophiolite, western Idaho, Blue Mountains island-arc complex (Triassic to Mississippian)
Jurassic marine wacke, volcanic, or carbonate metasediments of western Idaho.
Metasedimentary and metavolcanic rocks; Permian greenschist-facies rocks; western Idaho, Blue Mountains island-arc complex (Late Permian)
Upper Permian submarine volcanic complex in the Snake Canyon of western Idaho.
Metavolcanic and metasedimentary rocks, diorite, trondhjemite, and migmatite; Cretaceous to Jurassic quartz dioritic plutons in Mesozoic to Permian greenschist-facies rocks; western Idaho, Blue Mountains island-arc complex (Cretaceous to Permian)
Triassic and possibly Permian submarine metavolcanic rocks of west-central Idaho.
Metavolcanic and metasedimentary rocks; Jurassic greenschist-facies metamorphic rocks; western Idaho, Blue Mountains island-arc complex (Jurassic)
Jurassic mixed marine detrital and volcanic rocks of western Idaho.
Metavolcanic and metasedimentary rocks; Middle to Lower Triassic greenschist-facies metamorphic rocks; western Idaho, Blue Mountains island-arc complex (Middle and Early Triassic)
Middle and Lower Triassic metabasalt and submarine volcaniclastics of western Idaho
Mica schist, marble, quartzite, and amphibolite; Early Middle to Early Proterozoic metasedimentary rocks; southern Belt province (Early Middle Proterozoic to Early Proterozoic)
Older Precambrian high-grade metamorphic complex of eastern Idaho.
Mica schist, quartzite, and calc-silcicate rock; Proterozoic high-grade metasedimentary rocks; trans-Idaho metamorphic province (Proterozoic)
Precambrian high-grade metamorphic rock; metasediment; kyanite-sillimanite calc-silicate schist and gneiss, scapolite common
Mica schist, quartzite, gneiss, and amphibolite; Late to Early Proterozoic high-grade metasedimentary rocks (subunits are ZXmhs, ZXmhq, and ZXmhc); trans-Idaho metamorphic province (Proterozoic)
Precambrian high-grade metamorphic rock; metasediment
Mica schist, quartzite, migmatite, amphibolite; Middle to Early Proterozoic metamorphic rocks; northern Belt province, Spokane dome of Priest River metamorphic core complex (Middle Proterozoic to Early Proterozoic)
Precambrian, high-grade metamorphic rock; metasediment; kyanite-silimanite garnet-mica coarse-grained schist and gneiss; minor quartzite
Migmatitic paragneiss, quartzite, orthogneiss, and amphibolite; Early Proterozoic to Late Archean metamorphic rocks; northern Belt province; Settlement antiform in Priest River metamorphic core complex (Early Proterozoic to Late Archean)
Precambrian, high-grade metamorphic rock; metasediment; kyanite-sillimanite garnet-mica coarse-grained schist and gneiss; minor quartzite
Monzogranite, granodiorite, syenite, monzodiorite, monzonite, and diorite; Eocene phaneritic to porphyro-aphanitic intrusions (subunits are Teif and Teii); northern Idaho to central Idaho (Eocene)
Eocene intrusions including large granitic plutons and dike swarms of central Idaho
Orthogneiss, mica schist, and amphibolite; Early Proterozoic to Late Archean metamorphic rocks; south-central Idaho; Albion Range metamorphic core complex (Early Proterozoic to Late Archean)
Precambrian, high-grade metamorphic rock; metasediment subdivisions are (PC3, PC2, PC1).
Peraluminous monzogranite, granodiorite, pegmatite, aplite, and migmatite; mostly Cretaceous intrusions of the Kaniksu batholithic assemblage, but with minor Eocene intrusions, undivided; northern Idaho (Cretaceous to Eocene)
Cretaceous plutons; felsic; as granite or quartz monzonite; probably includes unmapped older and younger crystalline bodies.
Quartz diorite, metasedimentary rock, metavolcanic rock, and migmatite; Cretaceous to Jurassic plutons in Triassic to Permian metamorphic host rocks, undivided; western Idaho (Cretaceous to Permian)
Mixed, highly altered and migmatitic rocks; derived from imbrication and dynamic events
Quartz diorite, tonalite, granodiorite, orthogneiss, migmatite; Cretaceous to Jurassic quartz dioritic plutons; western Idaho, Blue Mountains island-arc complex (Early Cretaceous to Late Jurassic)
Lower Cretaceous to Upper Jurassic intrusions in west-central Idaho.
Quartzite and biotite schist in fault contact; Middle Proterozoic metasedimentary rocks; southern Belt province (Middle Proterozoic)
Intermediate Precambrian age metasediments; dominantly quartzite with minor micaceous layers and mica schists of northern Idaho
Quartzite, argillite, carbonate, meta-conglomerate, siltite, intermediate volcanic rock; Late Proterozoic rifted continental margin; southeastern Idaho (Late Proterozoic)
Younger Precambrian detrital units of central and southeastern Idaho; subdivisions are (Z2s and Z1s).
Quartzite, marble, Calc-silicate rock, schist, and meta-conglomerate; Ordovician to Middle Proterozoic metasedimentary rocks; central Idaho, Pioneer Mountains metamorphic core complex (Ordovician to Middle Proterozoic)
Ordovician to Middle Proterozoic metasedimentary rocks, undivided
Quartzite, meta-conglomerate, dolostone, argillite; Middle Proterozoic Swauger quartzite; southern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, red-tinted quartzite with minor conglomeratic and dolomitic lenses of southern Idaho
Quartzite, mica schist, and calc-silicate rock; Proterozoic high-grade metasedimentary rocks; trans-Idaho metamorphic province (Proterozoic)
Precambrian, high-grade metamorphic rock; metasediments; kyanite-sillimanite schist, and micaceous quartzite
Quartzite, mica schist, and marble; Cambrian and Late Proterozoic metasedimentary rocks; south-central Idaho, Albion-Range metamorphic core complex (Cambrian to Late Proterozoic)
Schist, quartzite and other metasediments of probable Lower Ordovician to Cambrian age.
Quartzite, siltite, argillite, and mica schist; Middle Proterozoic Lemhi Group; southern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, feldspathic quartzite and siltstone of southern Idaho.
Quartzite, siltstone, conglomerate, and metavolcanic rocks; Late and Middle Proterozoic, undivided; Atlanta batholith roof pendants (Late and Middle Proterozoic, undivided)
Precambrian, high-grade metamorphic rock
Quartz monzodiorite, monzogranite, granodiorite, monzonite, diorite; Eocene phaneritic to porphyro-aphanitic intrusions of the quartz monzodiorite suite; Challis magmatic belt (Eocene)
Eocene intrusions of intermediate (mafic to felsic) composition
Rhyolite, andesite, dacite, quartz latite; Oligocene to Eocene volcanics; northern Idaho; (Paleogene, possibly Oligocene)
Lower Tertiary, possibly Oligocene, flows and tuffs of northern Idaho.
Rhyolite flows and ignimbrites; Late Pleistocene felsic volcanics of subunit 3f; Yellowstone Plateau (Late Pleistocene)
Upper Pleistocene silicic volcanic unit 3 in eastern Idaho.
Rhyolite flows and ignimbrites; Late Pleistocene felsic volcanics; Yellowstone Plateau (subunits are Qpu1f and Qpu2f) (Late Pleistocene)
Upper Pleistocene silicic volcanic units; in eastern Idaho subdivisions are (Qpu3f, Qpu2f, Qpu1f)
Rhyolite ignimbrites, basalt flows, andesitic flows and tuffs, mudstone, conglomerate, and limestone; Quaternary to Tertiary volcanics and sediments; east-central Idaho (Pliocene)
Pliocene silicic welded tuff, ash, and flow rock; most common in southwestern Idaho.
Rhyolite ignimbrites, latite and basalt lava flows, late Eocene rhyolitic ignimbrite cauldron complex; east-central Idaho, northern Challis volcanic field (Eocene)
Eocene mixed silicic and basaltic volcanic ejecta, flows and reworked debris.
Rhyolite ot trachyte ignimbrites and flows; Pliocene felsic volcanics; eastern Snake River Plain and vicinity (Pliocene)
Pliocene silicic welded tuff, ash, and flow rock; most common in southwestern Idaho.
Rhyolite, quartz latite, and latite ignimbrites and flows; Miocene felsic volcanics; Owyhee Plateau; (Miocene)
Miocene silicic flows, tuffs; most common in southwestern Idaho.
Rhyolitic domes, flows, pyroclastic debris, and basalt flows; Early Pleistocene subvolcanic to volcanic features; eastern Snake River Plain (Early Pleistocene)
Lower Pleistocene to Pliocene silicic volcanic units near the Snake Plain.
Rhyolitic tuffs, ignimbrites, and flows, basaltic flows, conglomerate and marlstone; Pliocene to Miocene volcano-sedimentary deposits; eastern Snake River Plain and southeastern Idaho (Pliocene-Miocene)
Pliocene volcanic units, generally air-fall or pyroclastic in origin; grade into (Tpd).
Sandstone, conglomerate, siltstone, tuff, claystone, limestone, and diatomite; Pliocene tuffaceous alluvial and lacustrine deposits; Snake River Plain and vicinity, southeastern Idaho (Pliocene )
Pliocene stream and lake deposits; may be due to volcanic and block-faulting events.
Sandstone, limestone, and shale; Upper Triassic marine to non-marine epicontinental deposits; southeastern Idaho (Late Triassic)
Upper Triassic shallow-marine to non-marine sediments; oxidized shale, siltstone, limestone, and conglomeratic sandstone of eastern Idaho.
Sandstone, limestone, siltstone, shale, and conglomerate; Lower Permian to Middle Pennsylvanian deltaic turbidites; central Idaho; (Early Permian)
Lower Permian to Middle Pennsylvanian thrusted, marine detritus of central Idaho.
Sandstone, shale, siltstone, limestone, and coal; Late Cretaceous Cordilleran retroarc-foreland-basin deposits; southeastern Idaho (Late Cretaceous)
Upper Cretaceous thick detrital and fresh-water limestone beds of southeastern Idaho.
Sandstone, siltstone, dolostone, and chert; Pennsylvanian to Mississippian shallow marine inner continental-shelf deposits; eastern east-central Idaho (Pennsylvanian and Mississippian )
Pennsylvanian and Mississippian shallow-water carbonates of eastern Idaho.
Sandstone, siltstone, shale, limestone, and coal ; Early Cretaceous Cordilleran retroarc-foreland-basin deposits; southeastern Idaho (Early Cretaceous)
Lower Cretaceous shale, siltstone, red-bed sandstone and fresh-water limestone.
Schist, phyllite, quartzite, and calc-silicate rock; Middle Proterozoic metasedimentary rocks of Wallace Formation; northern Belt province (Middle Proterozoic)
Intermediate Precambrian age metasediments; generally low-to-medium grade; carbonate bearing argillite and siltite of northern Idaho.
Schist, quartzite, marble, skarn, and mafic gneiss; Jurassic to Mississippian amphibolite-facies rocks; southwestern Idaho, western accreted island-arc complex (Jurassic to Mississippian)
Metamorphic complex of probable Paleozoic units of southwestern Idaho.
Shale, arenite, conglomerate, intermediate and felsic volcanic rocks; Late Proterozoic rifted continental margin; southeastern Idaho (Late Proterozoic)
Younger Precambrian volcanic and diamictic units of central and southeastern Idaho.
Shale, arenite, siltstone, limestone, and chert; thrust-bounded Devonian to Ordovician deep-marine-basin deposits; central Idaho (Devonian and Silurian)
Devonian and Silurian thrusted, deep-water argillite beds of central Idaho.
Shale, conglomerate, sandstone, siltstone, limestone, and chert; Mississippian turbidite flysch from a western source; central Idaho (Mississippian)
Mississippian thrusted, shallow-to-deep marine detrital units of central Idaho.
Shale, limestone, and sandstone; Triassic marine to non-marine epicontinental deposits (subunits are TRl and TRu) (Triassic)
Triassic shallow-marine to non-marine sediments of eastern Idaho; subdivisions are (TRu and TRl).
Silt, clay, and diatomite; Middle Pleistocene lacustrine sediments of lava-dammed lakes; western Snake River Plain (Middle Pleistocene)
Middle Pleistocene lava-dammed Snake Plain lake beds of silt, clay and diatomite.
Silt, clay, sand, and gravel; Quaternary-Tertiary alluvial and lacustrine deposits; western Snake River Plain (Early Pleistocene and Late Pliocene)
Pleistocene and Pliocene stream and lake deposits.
Siltite, argillite, and quartzite; Middle Proterozoic Prichard Formation; northern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, gray interlaminated siltite and argillite with minor quartzite of northern Idaho.
Siltite, argillite, dolostone, and quartzite; Middle Proterozoic Wallace Formation; northern Belt province (Early Middle Proterozoic)
Intermediate Precambrian sediments, dark-colored calcareous and dolomitic argillite and siltite of northern Idaho.
Siltstone, evaporites, and redbeds; Late Jurassic Cordilleran retroarc-foreland-basin deposits; southeastern Idaho (Late Jurassic)
Upper Jurassic shallow-marine to non-marine sediments; glauconitic and variegated sandstone, siltstone and oolitic limestone of eastern Idaho.
Siltstone, sandstone, and dolostone; Early Permian marine epicontinental-basin deposits; southeastern Idaho (Early Permian)
Lower Permian beds; uppermost portion of the southern Idaho sequence (PPNs).
Siltstone, shale, and limestone; Early Triassic marine to non-marine epicontinental deposits; southeastern Idaho (Early Triassic)
Lower Triassic shallow-marine to non-marine sediments; limestone and chert above shaley sandstone, siltstone, and limestone of eastern Idaho.
Siltstone, shale, sandstone, and limestone; Jurassic Cordilleran retroarc-foreland-basin deposits (subunits are Jl and Ju); southeastern Idaho (Jurassic)
Jurassic shallow-marine to non-marine sediments of eastern Idaho; subdivisions are (Jl and Ju).
Syenite, granite, quartz syenite, and gabbro; Ordovician to Cambrian plutons; east-central Idaho (Ordovician to Cambrian)
Intrusive rock of eastern Idaho; appears older than Cretaceous; possibly Precambrian
Syenite, monzonite, quartz syenite; Late to Early Cretaceous syenitic intrusions; northern Idaho (Cretaceous)
Cretaceous syenitic to monzonitic intrusions
Syenite, quartz syenite, monzodiorite, quartz diorite, gabbro, pyroxenite, and hornblendite; Late Proterozoic plutons; east-central Idaho (Late Proterozoic)
Younger or Intermediate Precambrian age intrusive rock undifferentiated.
Trachyandesite, latite, trachybasalt flows, dikes, and volcaniclastic debris; Eocene intermediate volcanics; central Idaho, southern Challis volcanic field (Eocene)
Eocene mixed silicic and basaltic volcanic ejecta, flows and reworked debris.
Tuffaceous shale, sandstone, conglomerate, and lignite; Eocene to Pliocene alluvial and lacustrine deposits; central and southern Idaho (Tertiary)
Tertiary continental sediments; predominantly Upper Tertiary in age; subdivisions are:(Tpd, Tmd, and Ted).
Tuff, arkose, claystone, siltstone, conglomerate, lignite; Miocene alluvial and lacustrine deposits (Miocene)
Miocene stream and lake deposits; generally associated with volcanic episodes.
Illinois
Abbott Formation (Pennsylvanian)
Abbott Formation
Ancell Group (Ordovician)
Ancell Group
Bond Formation (Pennsylvanian)
Bond Formation
Cambrian (Cambrian)
Cambrian
Carbondale Formation (Pennsylvanian)
Carbondale Formation
Caseyville Formation (Pennsylvanian)
Caseyville
Cretaceous (Cretaceous)
Cretaceous
Galena-Platteville Groups (Ordovician)
Galena-Platteville Groups
Kinderhookian Series (Mississippian)
Kinderhookian Series
Lower Chesterian (Glen Dean - Renault) Series (Mississippian)
Lower Chersterian (Glen Dean - Renault) Series
Lower Devonian (Devonian)
Lower Devonian
Maquoketa Group (Ordovician)
Maquoketa Group
Mattoon Formation (Pennsylvanian)
Mattoon Formation
Middle Devonian (Devonian)
Middle Devonian
Middle Valmeyeran (Salem, Warsaw, Borden, Springville; includes thin Mvl and Mk in south and east) Series (Mississippian)
Middle Valmeyeran (Salem, Warsaw, Borden, Springville; includes thin Mvl and Mk in south and east) Series
Modesto Formation (Pennsylvanian)
Modesto Formation
Silurian (Silurian)
Silurian
Spoon Formation (Pennsylvanian)
Spoon (includes Pa in northeast)
Tertiary - Paleocene, Eocene (Tertiary)
Tertiary - Paleocene, Eocene
Upper Chesterian (Grove Church - Tar Springs) Series (Mississippian)
Upper Chesterian (Grove Church - Tar Springs) Series
Upper Devonian (Devonian)
Upper Devonian
Upper Valmeyeran (Aux Vases, Ste. Genevieve, St. Louis) Series (Mississippian)
Upper Valmeyeran (Aux Vases, Ste. Genevieve, St. Louis) Series
Indiana
Antrim Shale (Devonian)
Antrim Shale - Black shale; gray shale and limestone in lower part
Black River and Ancell Groups (Ordovician)
Black River and Ancell Groups - Dolomite, limestone, and sandstone
Bond Formation (Pennsylvanian)
Bond Formation - Mostly shale and sandstone; also includes thin beds of limestone and coal
Borden Group (Mississippian)
Borden Group - Mostly siltstone; lenses of crinodial limestone in upper part. Much cherty and silty limestone and dolomite in northwest. NP, top of New Providence Shale
Buffalo Wallow Group (Mississippian)
Buffalo Wallow Group - Mostly shale and sandstone; also includes thin beds of micritic limestone. L, Leopold Limestone member
Carbondale Group (Pennsylvanian)
Carbondale Group - Mostly shale and sandstone; also includes thin beds of limestone, clay, and coal. S, Springfield Coal Member
Knox Supergroup (Cambrian-Ordovician)
Knox Supergroup - P, base of Prairie du Chien Group
Mattoon Formation (Pennsylvanian)
Mattoon Formation - Mostly shale and sandstone; also includes thin beds of coal
Munising Group (Cambrian)
Munising Group - Shale, sandstone, limestone, and dolomite
Ordovician rocks, undifferentiated (Silurian)
Ordovician rocks, undifferentiated - Shale and limestone; upper part of Maquoketa Group in deep buried valleys; Maquoketa to upper part of Knox Supergroup in Kentland area
Patoka and Shelburn Formations (Pennsylvanian)
Patoka and Shelburn Formations - Mostly shale and sandstone; also includes thin beds of limestone and coal. WF, top of West Franklin member
Raccoon Creek Group (Pennsylvanian)
Raccoon Creek Group - Mostly shale and sandstone; also includes thin beds of limestone, clay, and coal. B, Buffaloville Coal Member; LB, Lower Block Coal Member
Salamonie Dolomite, Cataract Formation, and Brassfield Limestone (Silurian)
Salamonie Dolomite, Cataract Formation, and Brassfield Limestone
Stephensport Group (Mississippian)
Stephensport Group - Sandstone, micritic and skeletal limestone, and shale
West Baden Group (Mississippian)
West Baden Group - Shale, sandstone, and micritic and skeletal limestone
Whitewater Formation (Ordovician)
Whitewater Formation - Skeletal limestone and calcareous shale; dolomitic mudstone (S, Saluda Member) at base
Kansas
Admire Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late)
Includes: Grenola Limestone, Roca Shale, Red Eagle Limestone (base RE), Johnson Shale, Foraker Limestone (base FO), Janesville Shale with Five Point Limestone Member (base FP), Falls City Limestone, and Onaga Shale.
Alluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
unconsolidated sand, silt, clay, and gravel
Alluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
unconsolidated sand, silt, clay, and gravel
Carlile Shale (Phanerozoic | Mesozoic | Cretaceous-Late)
chalky shale with bentonite and thick chalk beds, dark gray fissile shale containing septarian concretions, and fine-grained sandstone.
Cherokee Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Early [Desmoinesian])
Includes: Cabaniss FM (base CA) with Verdigris Limestone Member (base V) and Mineral coal bed (base MC), Krebs FM with Bluejacket Sandstone Member (base BJ) and Warner Sandstone Member (base WR).
Dakota Formation (Phanerozoic | Mesozoic | Cretaceous-Early)
White, gray, red, brown and tan kaolinitic claystone, mudstone, shale and siltstone interbedded with grayish to yellowish brown thick lenticular sandstone beds. It also contains lignite and sandstone is commonly well cemented with iron oxide and calcite.
Douglas Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Virgilian])
Lawrence FM (base LA)- mostly gray shale and sandstone with minor red shale, coal, gray limestone and conglomerate, thickness ranges from 140ft to 250 ft. Stranger FM- five members containing sandstone, shale, and minor limestone, coal and conglomerate ranging from 100 ft. to 180 ft. thickness.
Drift (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
sand, silt, clay, and some gravel
Greenhorn Limestone and Graneros Shale (Phanerozoic | Mesozoic | Cretaceous-Late)
Greenhorn FM- thin bedded gray, chalky limestone and calcareous shale. Graneros Shale- fissile, noncalcareous, gray shale locally contains sandstone and siltstone beds.
Guadalupia Series: Big Basin Formation, Day Creek Dolomite, and Whitehorse Formation (Phanerozoic | Paleozoic | Permian [Custerian Cimarronian])
Big Basin FM- red silty shale, siltstone, dolomitic siltstone and fine-grained feldspathic sandstone. Day Creek Dolomite- light gray to pink, dense, fine-grained dolomite. Whitehorse FM- mostly red beds of feldspathic sandstone with some beds of siltstone and shale and minor dolomite.
Kansas City Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Missourian])
Includes: Lane Shale,Wyandotte Limestone (base WY), Liberty Memorial Shale, Iola Limestone (base I), Chanute Shale (base CH), Dewey Limestone, Nellie Bly FM, Cherryvale FM, Dennis Limestone (base DN), Galeburg Shale, Mound Valley Limestone, Ladore Shale, Swope Limestone (base SW), Elm Branch Shale, Hertha Limestone.
Kiowa Shale and Cheyenne Sandstone (Phanerozoic | Mesozoic | Cretaceous-Early)
Kiowa Shale or FM- light -gray to black illitic shale with thin coquinoidal limestone beds at the base; sandstone lenses common. Cheyenne Sandstone- massive to crossbedded, light-gray to buff fine-grained sandstone with lenses of gray sandy shale and conglomerate.
Lansing Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Missourian])
Stanton Limestone- three limestone and two shales members, ranges from 15 to 130 ft. thick. Vilas Shale- sandy, carbonaceous gray shale with some sandstone and limestone locally, ranges from 5 to 120 ft. thick. Plattsburg Limestone- two limestone members separated by shale, ranging from 25 to 115 ft. thick.
Marmaton Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Early [Desmoinesian])
Includes: Lost Branch FM, Memorial Shale, Lenapah Limestone (base LE), Nowata Shale, Altamont Limestone (base PA), Bandera Shale, Pawnee Limestone (base PA), Labette Shale and Fort Scott Limestone.
Meramecian and Osagian Series: Warsaw Limestone and Keokuk Limestone (Phanerozoic | Paleozoic | Carboniferous Mississippian [Osagian])
Warsaw Limestone- semigranular limestone interlaminated with saccharoidal dolomite with large amounts of gray chert; glauconite occurrs in the lower part. Keokuk Limestone- white tripolitic, chert, siliceous limestone, and dolomite
Nippewalla Group (Phanerozoic | Paleozoic | Permian [Custerian Cimarronian])
Dog Creek FM- maroon silty shale, siltstone, fine-grained feldspathic sandstone. Blaine FM- (base B) gypsum beds separated by dolomite and red shale. Flower Pot Shale -(base FL) red gypsiferous shale silty shale and minor sandstone and siltstone. Cedar Hills Sandstone- feldspathic sandstone, siltstone, and silty shale. Salt Plain FM- red flaky, silty shale and some siltstone with thick salt beds at base. Harper Sandstone with Kingman Sandstone member (base K)- red argillaceous siltstone and fine silty sandstone with a few beds of res shale and white sandstone. Stone Coral FM- dolomite, anhydrite, gypsum and salt.
Ogallala Formation (Phanerozoic | Cenozoic | Tertiary | Miocene)
massive to cross-bedded, generally arkosic sand, silt and gravel, locally cemented with calcium carbonate; also contains limestone, volcanic ash, diatomaceous marl, opaline sandstone and bentonitic clay
Pleasanton Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Missourian])
Includes: Shale Hill FM (base SH), and Hepler FM. Chiefly gray to very dark gray or yellowish gray shale with sandstone members and some limestone and coal.
Shawnee Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Virgilian])
Includes: Topeka Limestone, Calhoun Shale, Deer Creek Limestone (base DC), Tecumseh Shale, Lecompton Limestone (base LC), Kanwaka Shale, Oread Limestone with Plattsmouth Limestone Member (base PL).
Sumner Group (Phanerozoic | Paleozoic | Permian [Cimarronian])
Ninnescah Shale (base N)- mostly red silty shale with some gray shale , argillaceous limestone and dolomite. Wellington FM with Carlton Limestone Member (base CR)-mostly gray and some red shale with minor limestone and dolomite, siltstone, gypsum and anhydrite
Wabaunsee Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Virgilian])
Includes: Wood Siding FM, Root Shale, Stotler Limestone (base ST), Pillsbury Shale, Zeandale Limestone (base Z), Willard Shale, Emporia Limestone (base E), Auburn Shale, Bern Limestone (base BR), Scranton Shale, Howard Limestone (base H), and Severy Shale.
Kentucky
Alluvium (Pleistocene to Holocene)
Alluvium; includes glacial deposits along the Ohio River and its tributaries west of Cannelton locks
Ashlock Formation, Grant Lake and Calloway Creek Limestones, and Fairview Formation, undivided (Ordovician)
Ashlock Formation, Grant Lake and Calloway Creek Limestones, and Fairview Formation, undivided
Breathitt Formation, lower part (Pennsylvanian)
Breathitt Formation, lower part; lower part which includes Livingston Conglomerate Member of Lee Formation in eastern Rockcastle County
Breathitt Formation, middle part (Pennsylvanian)
Breathitt Formation, middle part
Breathitt Formation, upper part (Pennsylvanian)
Breathitt Formation, upper part
Carbondale Formation (Middle Pennsylvanian)
Carbondale Formation
Caseyville Formation (Lower to Middle Pennsylvanian)
Caseyville Formation
Continental deposits and loess, undifferentiated (Tertiary to Quaternary)
Continental deposits and loess, undifferentiated; West of the Tennessee River
Continental deposits, undifferentiated (Tertiary to Quaternary)
Continental deposits, undifferentiated; East of the Tennessee River
Cumberland Formation and Leipers and Catheys (?) Limestones, undivided (Ordovician)
Cumberland Formation and Leipers and Catheys (?) Limestones, undivided; in southernmost Kentucky
Drakes Formation (Ordovician)
Drakes Formation
Drakes Formation and Grant Lake and Calloway Creek Limestones, undivided (Ordovician)
Drakes Formation and Grant Lake and Calloway Creek Limestones, undivided; in Boyle, Casey, and Marion Counties
Garrard Siltstone and Kope and Clays Ferry Formations, undivided (Ordovician)
Garrard Siltstone and Kope and Clays Ferry Formations, undivided
High Bridge Group (Ordovician)
High Bridge Group
Jackson and Claiborne Formations, undivided (Tertiary)
Jackson and Claiborne Formations, undivided; includes some rocks of Oligocene age
Lee Formation (Mississippian to Pennsylvanian )
Lee Formation
Louisville Limestone and Waldron Shale, undivided (Silurian)
Louisville Limestone and Waldron Shale, undivided
Mauzy Formation (Lower Permian)
Mauzy Formation
Monongahela and Conemaugh Formations, undivided (Pennsylvanian)
Monongahela and Conemaugh Formations, undivided
New Albany, Chattanooga, and Ohio Shales, Boyle Dolomite (Limestone), and Sellersburg Limestone, undivided (Devonian to Mississippian)
New Albany, Chattanooga, and Ohio Shales, Boyle Dolomite (Limestone), and Sellersburg Limestone, undivided
Pennington Formation and Newman Limestone (Mississippian)
Pennington Formation and Newman Limestone; includes Carter Caves Sandstone in Carter County and vicinity
Pennington Formation, Newman Limestone, Fort Payne Chert, Grainger Formation, Sunbury Shale, Berea Sandstone, and Bedford Shale, undivided; Pennington Formation locally includes sandstone tongue of Lee Formation (Devonian to Pennsylvanian)
Pennington Formation, Newman Limestone, Fort Payne Chert, Grainger Formation, Sunbury Shale, Berea Sandstone, and Bedford Shale, undivided; Pennington Formation locally includes sandstone tongue of Lee Formation
Pennington Formation (Paragon Formation), Bangor Limestone, Hartselle Formation, and Kidder Limestone Member of Monteagle Limestone, undivided (Mississippian)
Pennington Formation (Paragon Formation), Bangor Limestone, Hartselle Formation, and Kidder Limestone Member of Monteagle Limestone, undivided
Preachersville Member of Drakes Formation and Bull Fork Formation, undivided (Ordovician)
Preachersville Member of Drakes Formation and Bull Fork Formation, undivided; in Bath and Montgomery Counties
Renfro and Muldraugh Members of Borden Formation and Fort Payne Formation, undivided (Mississippian)
Renfro and Muldraugh Members of Borden Formation and Fort Payne Formation, undivided
Rocks of Chesterian age, lower part (Upper Mississippian)
Rocks of Chesterian age, lower part
Rocks of Chesterian age, upper part (Upper Mississippian)
Rocks of Chesterian age, upper part
Salem, Warsaw, and Harrodsburg Limestones, undivided (Mississippian)
Salem, Warsaw, and Harrodsburg Limestones, undivided
Ste. Genevieve and St. Louis Limestones, undivided (Mississippian)
Ste. Genevieve and St. Louis Limestones, undivided; includes Salem Limestone west of Christian County
Sturgis Formation (Middle to Upper Pennsylvanian)
Sturgis Formation
Tradewater Formation (Middle Pennsylvanian)
Tradewater Formation
Wildie, Nada, Halls Gap, Holtsclaw Siltstone, Cowbell, Nancy, Kenwood Siltstone, New Providence Shale, Sunbury Shale, Berea Sandstone, and Bedford Shale, undivided; Borden Formation locally includes Renfro Member in eastern Kentucky (Devonian to Mississippian)
Wildie, Nada, Halls Gap, Holtsclaw Siltstone, Cowbell, Nancy, Kenwood Siltstone, New Providence Shale, Sunbury Shale, Berea Sandstone, and Bedford Shale, undivided; Borden Formation locally includes Renfro Member in eastern Kentucky
Louisiana
Alluvium (Phanerozoic | Cenozoic | Quaternary | Holocene)
gray to brownish gray clay and silty clay, reddish brown in the Red River Valley, some sand and gravel locally.
Blounts Creek Member (Phanerozoic | Cenozoic | Tertiary | Miocene Pliocene)
gray to green silty clays, siltstones, and silts with abundant sand beds; some lignite and lenses of black chert gravel.
Braided Stream Terraces (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
light gray, tan and brown fine to coarse sand; some clay silt and gravel.
Braided Stream Terraces (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
light gray, tan and brown fine to coarse sand; some clay silt and gravel. Overlain by 1-9 meters of loess.
Carnahan Bayou Member (Phanerozoic | Cenozoic | Tertiary | Miocene)
yellow to gray siltstones, sandstones, and clays with thin tuffaceous beds; some lenses of black chert gravel; petrified wood locally.
Catahoula Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene)
gray to white sandstones; loose quartz sand, tuffaceous sandstone, volcanic ash, and brown sandy clays; petrified wood locally.
Catahoula Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene)
gray to white sandstones; loose quartz sand, tuffaceous sandstone, volcanic ash, and brown sandy clays; petrified wood locally. Overlain by 1-9 meters of loess.
Cockfield Formation (Phanerozoic | Cenozoic | Tertiary | Eocene)
brown lignitic clays, silts and sands; some sideritic glauconite may weather to brown ironstone in lower part.
Deweyville Terrace (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
gray mixed with brown-to-red clay and silty clay; some sand and gravel locally.
Dough Hills Member (Phanerozoic | Cenozoic | Tertiary | Miocene)
gray to yellow silty clays; light gray calcareous clays which may weather to black soil; some siliceous silt and volcanic ash beds.
High Terraces (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
tan to orange clay, silt, and sand with a large amount of basal gravels.
High Terraces (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
tan to orange clay, silt, and sand with a large amount of basal gravels. Overlain by 1-9 meters of loess.
Intermediate Terraces (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
light gray to orange-brown clay, sandy clay, and silt; much sand and gravel locally.
Intermediate Terraces (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
light gray to orange-brown clay, sandy clay, and silt; much sand and gravel locally. Overlain by 1-9 meters of loess.
Jackson Group (undifferentiated) (Phanerozoic | Cenozoic | Tertiary | Eocene)
light gray to brown liginitic clays with thin interbeds of limonitic sands or lignite; near base,calcareous, glauconitic, and fossiliferous beds may weather to black soil.
Jackson Group (undifferentiated) (Phanerozoic | Cenozoic | Tertiary | Eocene)
light gray to brown liginitic clays with thin interbeds of limonitic sands or lignite; near base,calcareous, glauconitic, and fossiliferous beds may weather to black soil. Overlain by 1-9 meters of loess.
Lena Member (Phanerozoic | Cenozoic | Tertiary | Miocene)
gray calcareous clays which may weather to black soil; siltstone, taffaceous clays and some volcanic ash beds
Natural Levees (Phanerozoic | Cenozoic | Quaternary | Holocene)
gray and brown silt, silty clay, some very fine sand, reddish brown along the Red River.
Prairie Terraces (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
light gray to light brown clay, sandy clay, silt, sand, and some gravels.
Prairie Terraces (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
light gray to light brown clay, sandy clay, silt, sand, and some gravels. Overlain by 1-9 meters of loess.
Sparta Formation (Phanerozoic | Cenozoic | Tertiary | Eocene)
white to light gray massive sands with interbedded clays; some thin beds of lignite or lignitic sands and shales.
Vicksburg Group (undifferentiated) (Phanerozoic | Cenozoic | Tertiary | Oligocene)
brown to gray liginitic clays with thin interbeds of lignite or micaceous sands; calcareous shale, petrified wood, and bluish fossilferous clay locally.
Vicksburg Group (undifferentiated) (Phanerozoic | Cenozoic | Tertiary | Oligocene)
brown to gray liginitic clays with thin interbeds of lignite or micaceous sands; calcareous shale, petrified wood, and bluish fossilferous clay locally. Overlain by 1-9 meters of loess.
Wilcox Group (undifferentiated) (Phanerozoic | Cenozoic | Tertiary | Paleocene)
gray to brown lignitic sands and silty to sandy lignitic clays, many seams of lignite; some limestone and glauconite.
Williamson Creek Member (Phanerozoic | Cenozoic | Tertiary | Miocene)
white to gray silts, siltstones, silty clays, and sand beds; some lenses of black chert gravel.
Massachusetts
Ammonoosuc Volcanics (Middle Ordovician)
Ammonoosuc Volcanics - Amphibolite, felsic gneiss, garnet-amphibole quartzite, and marble too thin to show separately at map scale. Gedrite, anthophyllite, cummingtonite locally abundant in amphibolite layers.
Belchertown Complex (Devonian)
Belchertown Complex (intrudes De) - Intrusive breccia, mafic and ultramafic fragments in quartz diorite matrix.
Bellingham Conglomerate (Pennsylvanian, Cambrian or Proterozoic Z)
Bellingham Conglomerate - Red and gray metamorphosed conglomerate, sandstone, graywacke, and shale. Bellingham Conglomerate consists of conglomerate and lithic graywacke interbedded with chlorite phyllite and is confined to Bellingham basin. Also contains some volcanic rocks (rhyolite porphyry in roadcut on MA Hwy 146 at Premisy Hill west of Woonsocket, and felsite porphyry in the Franklin area east of Bellingham). Conglomerate contains pebbles of quartzite from adjacent Blackstone Group rocks and typical blue quartz of Milford Granite, so sediments are locally derived. Exposures on east side of Woonsocket Hill, southeast of Woonsocket, RI, show cliffs of steeply dipping, thin-bedded, white to gray quartzite of Blackstone Group standing above green schistose conglomerate containing many flattened white to gray quartzite pebbles and interbedded green calcareous quartz schist. Contact is probably a fault, but source of pebbles is quite obvious. In the same area, schist of Blackstone Group is difficult to distinguish from those of the Bellingham because of low-grade metamorphism of Blackstone rocks; it is probable that some of the low-grade Blackstone Rocks mapped northwest of Woonsocket in Blackstone River valley are part of Bellingham. The two rock units have been traditionally distinguished in the past by presence or absence of epidote (Warren and Powers, 1914), but this needs further study. Age is uncertain. Rocks have customarily been correlated with those of Pennsylvanian Narragansett basin; however, rocks in some exposures, such as the one at River St and Blackstone St in Woonsocket resemble Proterozoic Z Roxbury Conglomerate in Boston basin. Skehan and others (1979) suggest that Bellingham may have a similar age to that of Roxbury. This is supported by observation that Bellingham is a structural trough extending southwest from Boston basin and separating primarily Proterozoic Z granitoids from altered, but nongneissic, Proterozoic granitoids (Wones and Goldsmith, 1991). In deference to tradition, and because Proterozoic Z age has not been proven, age is shown on MA State bedrock map of Zen and others as Proterozoic Z to Pennsylvanian [map actually has age of Proterozoic Z, Cambrian, or Pennsylvanian, which differs from age stated in this report.] (Goldsmith, 1991).
Black and white, well-layered hornblende-biotite-plagioclase gneiss and amphibolite (Proterozoic Y)
Black and white, well-layered hornblende-biotite-plagioclase gneiss and amphibolite - Contains irregular pods of diopside or cummingtonite-talc rock or amphibole calc-silicate, epidote-layered quartz-plagioclase gneiss near Hinsdale.
Blackstone Group (Proterozoic Z)
Blackstone Group - Undivided - Quartzite, schist, phyllite, marble, and metavolcanic rocks.
Boylston Schist (Silurian or Ordovician)
Boylston Schist - Carbonaceous phyllite and schist, locally sulfidic; quartzite; calc-silicate beds.
Calc-silicate granofels and gneiss (Proterozoic Y)
Calc-silicate granofels and gneiss - Including calcitic or dolomitic chondrodite-diopside marble, coarse hornblende-plagioclase-diopside and diopside rock, locally containing beds of lustrous muscovite-kyanite sillimanite-garnet schist.
Cambridge Argillite (Proterozoic Z to earliest Paleozoic)
Cambridge Argillite - Gray argillite and minor quartzite; rare sandstone and conglomerate. Contains acritarchs. Cambridge Argillite of Boston Bay Group contains sandy horizons which are in some places quartzite. Most prominent are Milton quartzite unit of Billings (1976), and Tufts Quartzite Member (described by Billings, 1929, and LaForge, 1932) in northern part of basin. Red sandstone and sandy argillite in Chelsea, Revere, and Milton-Quincy areas intertongue with green argillite (Kaye, 1980). Red beds lie above cleaner quartzites such as Tufts and Milton units. Core analysis by D.A. Ashenden (Metropolitan District Commission, 1980, written commun.) indicates that Cambridge and Braintree Argillites are identical. Age of Boston Bay rocks has been controversial and was once thought to be Cambrian to Pennsylvanian (the latter based on lithologic similarity to rocks of Narragansett basin and now discredited plant fossils). Age of Cambridge and of Boston Bay Group as a whole is Proterozoic Z and possibly Early Cambrian based on presence of acritarchs in Cambridge. Acritarchs are diagnostic species that ranges in age from Proterozoic Z to Early Cambrian, but is most abundant in Proterozoic Z time (Lenk and others, 1982; [also see Goldsmith and others, 1982]). Age is also supported by the following: 1) plant fossils so numerous in strata of Narragansett basin are absent in the Boston Bay Group strata, 2) Late Ordovician and Early Silurian Quincy Granite contains argillite inclusions that are on strike with Cambridge Argillite, and 3) Boston Bay Group stratigraphy is primarily marine, not similar to terrestrial stratigraphy of Narragansett basin (Goldsmith, 1991).
Clough Quartzite (Upper Silurian)
Clough Quartzite - Quartz-pebble conglomerate, quartzite, and minor mica schist and calc-silicate rocks. Fossils at Bernardston are similar to those at Croyden Mountain, New Hampshire which indicate late Llandoverian age. Parts of the Littleton and Partridge Formations, and Clough Quartzite in MA are here reassigned to the Rangeley Formation [here geographically extended to MA]. The four mapped areas of Clough Quartzite in the Amherst area west of the Connecticut Valley border fault are now interpreted as conglomerate lenses in the Rangeley. Clough is considered the key stratigraphic unit in Bronson Hill anticlinorium because 1) it is dominated by distinctive, readily recognizable rock types, 2) where present, it is base of Silurian-Devonian sequence, resting with detectable unconformity on older rocks, and 3) it contains late Llandoverian fossils at several localities in western NH and adjacent VT, and at Bernardston, MA. Consists mostly of quartz-pebble conglomerate in which pebbles are typically deformed; other lithologies are quartz grit or white to pink, well-bedded quartzite. Locally contains some mica schist beds. On the MA State bedrock geologic map (Zen and others, 1983), thickness is locally exaggerated because at many localities, the unit was only a few meters or less thick and could not be shown at a scale of 1:250,000. Maximum thickness is 200 m on west limb of Northfield syncline. Unconformably overlies Fourmile Gneiss in Pelham dome and in Kempfield anticline, or Ammonoosuc Volcanics over most gneiss domes. Partridge Formation occurs along Clough-Ammonoosuc contact as lenses in many areas (Hatch and others, 1988).
Coal Mine Brook Formation (Middle Pennsylvanian)
Coal Mine Brook Formation - Fossiliferous, carbonaceous slate and garnet phyllite with a lens of meta-anthracite; conglomerate and arkose.
Cobble Mountain Formation (Middle Ordovician)
Cobble Mountain Formation - Light-brown, fine- to medium-grained pelitic schist and granofels locally graded in beds less than 15 cm thick. Local amphibolite. Rare calc-silicate rock, feldspar gneiss, coticule and cummingtonite schist.
Cobble Mountain Formation (Middle Ordovician)
Cobble Mountain Formation - Red rusty-weathering schist containing thin beds of white quartz-plagioclase granofels and vitreous quartzite. Local amphibolite and thin anthophyllite amphibolite.
Cobble Mountain Formation (Middle Ordovician)
Cobble Mountain Formation - Thick-bedded (15 to 40 cm), nonrusty-weathering, silvery-gray, medium- to coarse-grained mica gneiss interlayered with nonrusty-weathering mica schist and minor amphibolite.
Collinsville Formation (Middle Ordovician or older)
Collinsville Formation - Amphibolite and minor plagioclase gneiss. Magnetite-hornblende granofels near top.
Collinsville Formation (Middle Ordovician or older)
Collinsville Formation - Interlayered amphibolite and white felsic gneiss containing biotite, hornblende, and magnetite. Local calc-silicate beds. Coticule-bearing granofels, muscovite quartzite and amphibolite in upper part.
Collinsville Formation (Middle Ordovician or older)
Collinsville Formation - Interlayered amphibolite and felsic gneiss in beds less than 1 m thick. Local, coarse-grained magnetite-hornblende gneiss.
Cooleyville Granitic Gneiss (Devonian)
Cooleyville Granitic Gneiss - Biotite tonalite to granite in composition, strongly foliated and lineated; contains inclusions of Dpgb; intrudes Dl.
Cretaceous sediments (Cretaceous)
Cretaceous sediments - Clay, silt, sand, and gravel, mostly of non-marine and nearshore marine origin, Campanian and older.
Dalton Formation (Lower Cambrian and Proterozoic Z)
Dalton Formation - Orangish-gray, gray, and light-greenish-gray muscovite-quartz schist and interlayered feldspathic quartzite and quartz conglomerate; minor beds of rusty albitic schist.
Dalton Formation (Lower Cambrian and Proterozoic Z)
Dalton Formation - Tan to orangish-tan quartz and gneiss cobble and pebble conglomerate, rusty feldspathic schist, and lustrous greenish-gray muscovite quartz schist.
Dedham Granite (Proterozoic Z)
Dedham Granite - Light grayish-pink to greenish-gray, equigranular to slightly porphyritic, variably altered, granite south and west of Boston. Includes dioritic rock near Scituate and Cohasset and Barefoot Hills Quartz Monzonite of Lyons (1969) and Lyons and Wolfe (1971). Intrudes Zdi, Zgb, Zb, Zv. Extensive calc-alkaline plutons separated by Boston basin have long been mapped as Dedham. Those to the north of Boston and studied in this report, are referred to as Dedham North. Crystallization ages for the Dedham North suite (based on titanites and zircons) have been determined at 607+/-4 Ma, while ages for the Lynn are slightly younger at 596+/-3 Ma. Both are clearly part of the Late Proterozoic magmatic event. Dates on two samples from Sheffield Heights indicate that the diorite and granite are part of the Dedham North suite. The Dedham south and west of Boston has been dated at 630+/15 Ma (Zartman and Naylor, 1984). Dedham North Granite has a compositionally highly variable suite ranging from leucogranites to granodiorites, tonalites, and quartz diorite. The granites originated by partial melting of a sedimentary protolith, while the intermediate members show a mixing of granitic magma and mafic magma (Hepburn and others, 1993).
Diorite (Proterozoic Z)
Diorite - Medium-grained hornblende diorite metamorphosed in part to amphibolite and hornblende gneiss.
Diorite and gabbro (Proterozoic Z)
Diorite and gabbro - Complex of diorite and gabbro, subordinate metavolcanic rocks and intrusive granite and granodiorite.
East Berlin Formation (Lower Jurassic)
East Berlin Formation - Reddish-brown to pale red arkosic sandstone and siltstone, and gray sandstone, gray mudstone, and black shale; interpreted as lake beds. Assigned to Newark Supergroup (Robinson and Luttrell, 1985). The East Berlin Formation of the Hartford basin contains eight facies: trough cross-bedded sandstones, horizontally stratified sandstones, interbedded sandstones and mudrocks, ripple cross-laminated siltstones, black shales, stratified mudrocks, disrupted shales, and disrupted mudstones. These facies are interpreted as a continental depositional system and are divided into two assemblages. Sandflat/alluvial plain facies assemblage (sandstones and siltstones) is composed of sheet-flood deposits. The lacustrine assemblage (shales and mudrocks) represents a saline lake-playa system (Gierlowski-Kordesch, and Rust, 1994).
Erving Formation (Lower Devonian)
Erving Formation - Biotite-plagioclase granofels, minor mica schist and calc-silicate granofels, and layers of epidote amphibolite.
Fitchburg Complex (Lower Devonian or younger)
Fitchburg Complex -Dark-gray, strongly foliated biotite granodiorite to tonalite gneiss; resembles Dht; intrudes and contains inclusions of Dl, some mappable; locally cut by sills identical to Dfgrg.
Fitchburg Complex (Lower Devonian or younger)
Fitchburg Complex - Light-gray, strongly foliated biotite-muscovite granite to granodiorite gneiss; common small to very large inclusions of Dl, some mapped separately.
Fitchburg Complex (Lower Devonian or younger)
Fitchburg Complex - Dfgd containing many zones of foliated biotite-muscovite granite gneiss and inclusions of mica schist and feldspathic granulite.
Fitch Formation (Upper Silurian)
Fitch Formation - Calc-silicate granofels, biotite granofels, minor sulfidic schist and marble. Correlated with the fossiliferous Fitch Formation of western New Hampshire. Although the text and figures of this report show the Fitch as Silurian, a footnote [added just before this report went to press] cites a change in age from Silurian to Early Devonian based on conodonts found at the Bernardston, MA, locality, as reported in Elbert and others (1988). In Bronson Hill anticlinorium in MA, Fitch occurs as lenses between Clough Quartzite and Littleton Formation. Most common rock types in MA are gray, massive to weakly bedded, quartz-labradorite-biotite granulite containing a moderate amount of some combination of calc-silicate minerals (calcic amphibole, zoisite or clinozoisite, diopside, sphene, and microcline); commonly interbedded with biotite-free granulite that contains same calc-silicate minerals. One small exposure consists of nearly pure calcite marble. Larger lenses of Fitch consist of varieties of schist, similar to Partridge Formation. Best exposures are in low hills west of village of Orange, northeast of junction of MA Hwys 2A and 78. As shown on MA State bedrock geologic map, Fitch everywhere overlies Clough Quartzite and is never in contact with Partridge. Fossils dating the Fitch as Pridolian (Harris and others, 1983) are all from Littleton, NH, area [however, see mention of footnote, above] (Hatch and others, 1988).
Gabbro (Proterozoic Z)
Gabbro - Hornblende gabbro and hornblende-pyroxene gabbro metamorphosed in part to hornblende gneiss and amphibolite.
Gile Mountain Formation (Lower Devonian)
Gile Mountain Formation - Gray, slightly rusty, poorly bedded phyllite and schist containing 20 cm to 2 m beds of light-gray, fine-grained quartzite, local punky-brown weathering calcareous granofels or quartzose marble, and pods and stringers of vein quartz.
Gile Mountain Formation (Lower Devonian)
Gile Mountain Formation - Like Dgm but having a higher percentage of quartzite.
Gneiss and schist near New Bedford (Proterozoic Z)
Gneiss and schist near New Bedford - Hornblende and biotite schist and gneiss, amphibolite.
Goshen Formation (Lower Devonian)
Goshen Formation - Dg containing beds of punky-weathering calcareous granofels more than 15 cm thick near the contact with the Waits River Formation.
Goshen Formation (Lower Devonian)
Goshen Formation - Similar to Dg but having scattered beds of calcareous granofels.
Goshen Formation (Lower Devonian)
Goshen Formation - Light gray-brown micaceous quartzite and quartz-mica-garnet schist in beds as much as 6 m thick. Calc-silicate granofels and rare punky-weathering calcareous granofels.
Granite, gneiss, and schist, undivided (Proterozoic Z)
Granite, gneiss, and schist, undivided - Plutonic and metamorphic rocks of probable Proterozoic Z age. May include plutonic and volcanic rocks of Paleozoic or younger age.
Gray, well-layered biotite-plagioclase-quartz gneiss (Proterozoic Y)
Gray, well-layered biotite-plagioclase-quartz gneiss - Containing beds of amphibolite, aluminous schist, quartzite, and calc-silicate gneiss.
Gray, well-layered biotite-plagioclase-quartz gneiss (Proterozoic Y)
Gray, well-layered biotite-plagioclase-quartz gneiss - Ybu may contain undifferentiated areas of Ycs, Yl, and Yhb.
Greylock Schist (Lower Cambrian and Proterozoic Z)
Greylock Schist - Light-green to gray, white albite-spotted phyllite and interbedded blue-quartz metagraywacke, salmon-pink dolostone, and blue-quartz conglomerate. Minor interbeds of black and white albite-spotted phyllite resembles Hoosac (CAZhga).
Hawley Formation (Middle Ordovician)
Hawley Formation - Interbedded amphibolite, greenstone, feldspathic schist and granofels. Coarse plagioclase in some amphibolite near top; local coarse hornblende blades or sprays. Sparse coticule (Emerson, 1917, p. 43). As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).
Hawley Formation (Middle Ordovician)
Hawley Formation - Black, fine-grained, splintery, rusty-weathering schist and thin dark quartzite; interlayered amphibolite commonly has plagioclase megacrysts. As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).
Hawley Formation (Middle Ordovician)
Hawley Formation - Medium-gray plagioclase-hornblende-chlorite schist containing megacrysts of plagioclase and angular fragments of feldspar granofels, epidote-plagioclase granofels, and dark-gray amphibolite. As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).
Hoosac Formation (Lower Cambrian and Proterozoic Z)
Hoosac Formation - Undifferentiated Hoosac Formation.
Hoosac Formation (Lower Cambrian and Proterozoic Z)
Hoosac Formation - Rusty-brown to dark-gray, albite-spotted muscovite-biotite schist or gneiss, with interlayered black garnet-biotite-albite-quartz schist near base; interfingers with Dalton Formation.
Hoosac Formation (Lower Cambrian and Proterozoic Z)
Hoosac Formation - Light-gray, albite-biotite granofels and schist, pseudoconglomerate and blue quartz pebble conglomerate.
Hoosac Formation (Lower Cambrian and Proterozoic Z)
Hoosac Formation - Green to gray-green chlorite-sericite-quartz phyllite; interbeds of chloritoid- or albite-rich schist and minor quartzite, locally rich in garnet and kyanite.
Hoppin Formation (Middle and Lower Cambrian)
Hoppin Formation - Quartzite, argillite, and minor limestone; contains Middle Cambrian fauna.
Intimately interfolded Littleton and Partridge Formations (Lower Devonian and Middle Ordovician)
Intimately interfolded Littleton and Partridge Formations - In areas of poor exposure and incomplete mapping.
Kittery Formation (Silurian or Ordovician)
Kittery Formation - Quartzite, partly calcareous; phyllite, schist.
Lynn Volcanic Complex (Lower Devonian, Silurian, or Proterozoic Z)
Lynn Volcanic Complex - Rhyolite, agglomerate and tuff.
Marlboro Formation (Ordovician, Cambrian, or Proterozoic Z)
Marlboro Formation - Thinly layered amphibolite, biotite schist and gneiss, minor calc-silicate granofels and felsic granofels.
Mattapan Volcanic Complex (Proterozoic Z or younger)
Mattapan Volcanic Complex - Rhyolite, melaphyre, agglomerate, and tuff. Mattapan Volcanic Complex is found in west and southwest part of Boston basin and beyond, and to the south in Blue Hills. Similar in lithology to Lynn Volcanic Complex. Both units consist largely of partly porphyritic rhyolite and rhyodacite flows, welded ash-flow tuffs, vitric tuff, lapilli tuff, lithic tuff, flow breccias, breccia pipes, and extrusion domes. Mattapan's rhyolite and rhyodacites are thinner and less varied in composition and texture than Lynn's, and volcanic breccias are absent in Lynn. Both units are reported to lie nonconformably on Dedham Granite and unnamed plutonic-volcanic complex of eastern MA; however, Mattapan has been observed as dikes and stocks cutting Dedham Granite (Billings, 1976; Kaye and Zartman, 1980; Chute, 1966), and other workers have pointed out evidence that some of Mattapan may be penecontemporaneous with younger phases of Dedham batholith. Westwood Granite may be intrusive equivalent of Mattapan. Mattapan is conformably and fairly continuously overlain by Roxbury Conglomerate of Boston Bay Group. LaForge (19832) cautioned against identifying rocks interbedded within Mattapan that look like Roxbury, but are still part of Mattapan. Metavolcanic rocks in Blue Hills resembling Mattapan are assigned to Mattapan on State bedrock map (Zen and others, 1983); for years they were considered to be either Silurian and Devonian, or Carboniferous; however, they are chemically and mineralogically distinct from Ordovician and Silurian Blue Hills [sic] Granite Porphyry. Author follows usage of Chute (1966) who could find no difference between volcanic rocks in Blue Hills area and Mattapan rocks, and thus these rocks are assigned to Mattapan. Proterozoic Z age is based on U-Th-Pb zircon date of 602 +/-3 Ma (Zartman, in Kaye and Zartman, 1980). Although Billings (1979) questions reliability of zircon ages from volcanic rocks, discovery of Proterozoic Z acritarchs in overlying Cambridge Argillite indicates zircon age is appropriate (Goldsmith, 1991).
Metamorphosed mafic to felsic flow, and volcaniclastic and hypabyssal intrusive rocks (Proterozoic Z)
Metamorphosed mafic to felsic flow, and volcaniclastic and hypabyssal intrusive rocks - Includes some diorite and gabbro north and northwest of Boston.
Monson Gneiss (Ordovician, Cambrian, or Proterozoic Z)
Monson Gneiss - Layered to massive biotite-plagioclase gneiss, amphibolite, microcline augen gneiss.
Moretown Formation (Middle Ordovician or older)
Moretown Formation - Nubble garnet schist, pinstriped granofels, and fine-grained amphibolite in equal parts.
Mount Mineral Formation (Proterozoic Z)
Mount Mineral Formation (Probably correlates with Poplar Mountain Gneiss but is more aluminous) - Aluminous schist, amphibolite, and quartzite, undifferentiated; locally rich in garnet and kyanite, and with relict sillimanite and orthoclase from pre-Middle Ordovician metamorphism.
Mount Toby Formation (Lower Jurassic)
Mount Toby Formation - Reddish-brown to pale red arkosic sandstone, and gray sandstone, gray siltstone, and black shale interpreted as lake beds.
Nashoba Formation (Ordovician or Proterozoic Z)
Nashoba Formation - Sillimanite schist and gneiss, partly sulfidic, amphibolite, biotite gneiss, calc-silicate gneiss and marble. Nashoba Formation occurs in Nashoba zone of eastern MA. Consists of interlayered sillimanite-bearing, partly sulfidic schist and gneiss, calc-silicate gneiss, and subordinate quartzite and marble. Protoliths were probably volcanogenic sediments interlayered with limy marine sediments. Bell and Alvord (1976) divided Nashoba into 10 members on basis of lithology. Amphibolite is most abundant near presumed base, namely in Boxford Member. Skehan and Abu-Moustafa (1976) divided Nashoba into 30 members based on section in Wachusett-Marlborough tunnel. Although Bell and Alvord's and Skehan and Moustafa's sections contain similar lithologies, Bell and Alvord's is much thicker, and Boxford Member is not readily identified in Skehan and Abu-Moustafa's. Subdivision of Nashoba is conjectural south of Marlborough and Shrewsbury. On MA State bedrock map (Zen and others, 1983) only Boxford Member is separated out from the rest of the Nashoba because this unit was the only member clearly recognized in several area. A definite sequence of members probably does not exist anywhere in the Nashoba because of lenticularity of assemblages and repeated rock types, both of which could be accounted for by either sedimentary or tectonic processes. Although Castle (1965) considered Fish Brook to be either a premetamorphic intrusive rock or a core gneiss of intrusive or sedimentary ancestry, Bell and Alvord (1976) considered it to be volcanic or volcaniclastic in origin. Zircons in Fish Brook are certainly volcanic in origin and yield a date of 730 +/-26 Ma (Olszewski, 1980). If the rock were a core gneiss, that date would apply only to the Fish Brook and not to surrounding rocks; but, Bell and Alvord (1976) believe Fish Brook to be part of the Marlboro Formation-Nashoba Formation sequence and therefore the date does apply to the sequence. In addition, a 1500 Ma date for Shawsheen Gneiss [reference not given] helps bracket age of Marlboro-Nashoba sequence. An upper limit for the sequence was established from the 430 +/-5 Ma age of intruding Sharpers Pond Diorite and 450 +/-23 Ma age of the intruding Andover Granite (Zartman and Naylor, 1984). Although age on MA State bedrock map is shown as Proterozoic Z or Ordovician (due to uncertainty regarding actual rocks sampled by Olszewski and a strong belief that rocks of Nashoba zone correlated with Ordovician rocks to the west), author now feels that rocks of Nashoba zone (except for Tadmuck Brook Schist) are all Proterozoic, but that they are unlike the Proterozoic rocks of neighboring Milford-Dedham zone. [no formal age change made in this report] (Goldsmith, 1991).
Nassau Formation (Lower Cambrian and Proterozoic Z)
Nassau Formation - Gray to dark-greenish-gray, siliceous phyllite with abundant beds of quartzite, olive-gray metasiltstone and subgraywacke (includes Bomoseen Graywacke Member and Zion Hill quartzite Member).
Newbury Volcanic Complex (Lower Devonian and Upper Silurian)
Newbury Volcanic Complex - Lower members. Basalt, andesite, rhyolite, and tuff.
New Haven Arkose (Upper Triassic)
New Haven Arkose - Red, pink, and gray coarse-grained, locally conglomeratic arkose interbedded with brick-red shaley siltstone and fine-grained arkosic sandstone; boundary between Lower Jurassic (Jn) and Upper Triassic (TRn) parts is arbitrarily drawn through clastic rocks of similar lithology below gray mudstone containing Lower Jurassic palynofloral zone; TRn is continuous with and lithically similar to TRs near Northampton. Assigned to Newark Supergroup (Robinson and Luttrell, 1985).
New Haven Arkose (Lower Jurassic)
New Haven Arkose - Red, pink, and gray coarse-grained, locally conglomeratic arkose interbedded with brick-red shaley siltstone and fine-grained arkosic sandstone; boundary between Lower Jurassic (Jn) and Upper Triassic (TRn) parts is arbitrarily drawn through clastic rocks of similar lithology below gray mudstone containing Lower Jurassic palynofloral zone. Assigned to Newark Supergroup (Robinson and Luttrell, 1985).
Partridge Formation (Middle Ordovician)
Partridge Formation (includes Brimfield Schist of Emerson, 1917) - Mafic and felsic gneisses of volcanic derivation with calc-silicate granofels.
Partridge Formation (Middle Ordovician)
Partridge Formation (includes Brimfield Schist of Emerson, 1917) - Biotite gneiss of volcanic derivation, minor amphibolite and sulfidic schist.
Plainfield Formation (Proterozoic Z)
Plainfield Formation - Quartzite, pelitic schist, minor calc-silicate rock and amphibolite. Plainfield Formation extend into MA in Webster-Oxford area from eastern CT and western RI along west flank of Rhode Island batholith, along same strike as elongate lenses of Westboro Formation (as shown on State bedrock map of Zen and others, 1983). Lithology of Plainfield in New London area of southeastern CT (Goldsmith, 1966, 1976) and in eastern CT (Harwood and Goldsmith, 1971), and its structural and stratigraphic position indicate Plainfield and Westboro are equivalent. Plainfield is truncated along CT-RI border by Lake Char fault; however, in New London area, Plainfield is overlain by suite of largely mafic metavolcanic rocks (Waterford Group of Goldsmith, 1980), a relationship similar to that of the Westboro Formation and overlying metavolcanic rocks. Base of Plainfield is unknown, but gneiss and schist in center of Lyme dome may lie below it. Probably equivalent to quartzite and schist of Blackstone Group on basis of similar lithology and structural relations with Rhode Island batholith rocks (Goldsmith, 1991).
Portland Formation (Lower Jurassic)
Portland Formation - Reddish-brown to pale red arkose and siltstone, and gray sandstone, gray siltstone, and black shale interpreted as lake beds.
Quinebaug Formation (Ordovician, Cambrian, or Proterozoic Z)
Quinebaug Gneiss - Amphibolite, biotite and hornblende gneiss, felsic gneiss, and calc-silicate gneiss.
Red arkosic conglomerate, sandstone, and siltstone (Upper Triassic)
Red arkosic conglomerate, sandstone, and siltstone - In Essex County.
Reubens Hill Formation (Silurian or Ordovician)
Reubens Hill Formation - Amphibolite, hornblende-chlorite schist, and feldspathic schist. Includes metamorphosed diorite.
Rhode Island Formation (Upper and Middle Pennsylvanian)
Rhode Island Formation - Conglomerate, sandstone, and graywacke. Rhode Island Formation is thickest and most extensive formation in Narragansett basin. Does not extend to Norfolk basin. Consists of gray sandstone and siltstone and lesser amounts of gray to black shale, gray conglomerate, and coal beds 10 m thick. Interfingers with Wamsutta Formation in Narragansett basin. In places overlies Dedham Granite. Age is Middle and Late Pennsylvanian (Goldsmith, 1991).
Rhode Island Formation (Upper and Middle Pennsylvanian)
Rhode Island Formation - Sandstone, graywacke, shale and conglomerate; minor beds of meta-anthracite. Fossil plants. Rhode Island Formation is thickest and most extensive formation in Narragansett basin. Does not extend to Norfolk basin. Consists of gray sandstone and siltstone and lesser amounts of gray to black shale, gray conglomerate, and coal beds 10 m thick. Interfingers with Wamsutta Formation in Narragansett basin. In places overlies Dedham Granite. Age is Middle and Late Pennsylvanian (Goldsmith, 1991).
Roxbury Conglomerate (Proterozoic Z to earliest Paleozoic)
Roxbury Conglomerate - Conglomerate, sandstone, siltstone, argillite, and melaphyre. Consists of Brookline, Dorchester, and Squantum Members. Roxbury Conglomerate forms base of Boston Bay Group. Divided into Brookline, Dorchester, and Squantum Members. Conglomerate in Brookline Member contains clasts of Dedham Granite, quartzite (possibly from Westboro Formation), and volcanic rock from underlying Mattapan Volcanic Complex. Dorchester Member consists of interbedded argillite and sandstone and forms an intermediate unit between Brookline Member and overlying Cambridge Argillite. Uppermost Squantum Member is a distinctive diamictite which appears to pinch out in northern part of basin. Brighton Melaphyre lies within Brookline Member and consists of mafic volcanic rocks (quartz keratophyre, keratophyre, and spilite). Roxbury clearly lies nonconformably on Dedham Granite near Hull, MA; can be traced continuously over Mattapan Volcanic Complex. Age is Proterozoic Z and possibly Early Cambrian (Goldsmith, 1991).
Russell Mountain Formation (Silurian)
Russell Mountain Formation - Quartzite, calc-silicate granofels, and calc-silicate marble. Correlated with the fossiliferous Shaw Mountain Formation of eastern Vermont. In original definition of Russell Mountain Formation (Hatch and others (1970), calcareous granofels on Woronoco dome was included in unit. Subsequent mapping by Stanley and others (1982) indicates that rocks mapped on Woronoco dome are different from the rest of Russell Mountain Formation and are more logically included in overlying Lower Devonian sequence (mapped as an unnamed member of Goshen Formation in fig. 3). Other than this modification and mapping a few lenses of Russell Mountain Formation just north of Massachusetts Turnpike, original definition of Russell Mountain stands. Thickness does not exceed 35 m, but its correlative in CT, the basal member of The Straits Schist of Rodgers (1982, 1985), is locally at least twice as thick. Has not been shown to correlate with either Clough Quartzite or Fitch Formation to the east. Russell Mountain Formation is highly discontinuous except near Shelburne Falls dome. Locally overlies members A and D of Cobble Mountain Formation; overlain everywhere by Goshen Formation. Silurian age is based on correlation with discontinuous lenses of similar rocks at same stratigraphic position as Shaw Mountain Formation of VT. Recent field trips with J.B. Thompson, Jr. (Harvard University) and others has raised questions as to whether many of those rocks in southern VT are actually Shaw Mountain. Shaw Mountain Formation has been assigned a firm age of late Llandoverian to Gedinnian north of Albany, VT, based on HOWELLELA (Boucot and Thompson, 1963; Konig, 1961) (Hatch and others, 1988).
Shuttle Meadow Formation (Lower Jurassic)
Shuttle Meadow Formation - Reddish-brown to pale red arkosic sandstone and siltstone, and gray sandstone, gray mudstone, and black shale; interpreted as lake beds. The Shuttle Meadow Formation is assigned to Newark Supergroup and is extended into MA in the Hartford basin. It consists of sandstone strata containing one interval of gray mudstone beds. The unit grades eastward along strike into a conglomeratic facies. It overlies the New Haven Arkose or Hitchcock Volcanics and underlies the Holyoke Basalt (Robinson and Luttrell, 1985).
Stockbridge Formation (Lower Cambrian)
Stockbridge Formation - Beige, tan, and dark-gray weathering quartzose dolomite marble containing interbeds of black, green and maroon phyllite and punky weathering blue quartz pebble quartzite.
Stockbridge Formation (Lower Ordovician)
Stockbridge Formation - Blue and gray mottled limestone and calcite marble and beds of beige dolostone.
Sugarloaf Formation (Upper Triassic)
Sugarloaf Formation - Red, pink, and gray coarse-grained, locally conglomeratic arkose, interbedded with brick-red shaley siltstone and fine-grained arkosic sandstone; boundary between Lower Jurassic (Js, Jsc) and Upper Triassic (TRs) parts are arbitrarily drawn through rocks of similar lithology on basis of Lower Jurassic palynofloral zone in gray mudstone immediately below Deerfield (Jdb); TRs is continuous with and lithically similar to TRn near Northampton. Assigned to Newark Supergroup and revised to include all sedimentary strata in the Deerfield basin below the Deerfield Basalt or its projected horizon. The Late Triassic-Early Jurassic boundary is arbitrarily drawn through clastic rocks consisting of coarse-grained, locally conglomeratic arkose interbedded with sandstone and siltstone below a Lower Jurassic palynofloral zone in gray mudstone just below the base of the Deerfield Basalt. The Sugarloaf is continuous with and lithologically similar to the New Haven Arkose in the Hartford basin (Robinson and Luttrell, 1985).
Sugarloaf Formation (Lower Jurassic)
Sugarloaf Formation - Reddish-brown to pale red arkose, and gray sandstone, gray siltstone, and black shale interpreted as lake beds.
Tadmuck Brook Schist (Silurian?, Ordovician, or Proterozoic Z)
Tadmuck Brook Schist - Andalusite phyllite and sillimanite schist, partly sulfidic; local quartzite in upper part.
Tatnic Hill Formation (Ordovician or Proterozoic Z)
Tatnic Hill Formation - Sulfidic sillimanite schist, sillimanite schist and gneiss, biotite gneiss; minor amphibolite, calc-silicate gneiss and marble.
Tertiary sediments (Tertiary)
Tertiary sediments - Unconsolidated sand, silt, and clay in discontinuous patches; contains Tertiary fossils; may include Pleistocene sediments (cross section only).
Turner Falls Sandstone (Lower Jurassic)
Turner Falls Sandstone - Reddish-brown to pale red arkosic sandstone, and gray sandstone, gray siltstone, and black shale interpreted as lake beds.
Undifferentiated Poplar Mountain and Dry Hill Gneisses (Proterozoic Z)
Undifferentiated Poplar Mountain and Dry Hill Gneisses .
Vaughn Hills Quartzite (Silurian or Ordovician)
Vaughn Hills Quartzite - Quartzite, phyllite, conglomerate, and chlorite schist.
Waits River Formation (Lower Devonian)
Waits River Formation - Interbedded medium- to dark-gray, moderately rusty weathering, highly contorted, unbedded schist and punky-weathering calcareous granofels or quartzose marble, and pods and stringers of vein quartz.
Waits River Formation (Lower Devonian)
Waits River Formation - Dw containing thick (1 m) beds of calcareous granofels. Mapped only in Colrain quadrangle; included in Dw elsewhere.
Walloomsac Formation (Middle Ordovician)
Walloomsac Formation - Dark-gray, graphitic quartz phyllite and schist containing minor lenses of limestone.
Wamsutta Formation (Middle and Lower Pennsylvanian)
Wamsutta Formation - Red to pink, well-sorted conglomerate, graywacke, sandstone, and shale; fossil plants. Wamsutta Formation occurs in Narragansett and Norfolk basins. Consists of conglomerate, lithic graywacke, sandstone, and shale. Also contains rhyolite and basalt horizons near Attleboro. Northwest of Attleboro, Wamsutta overlies Diamond Hill Felsite as used by Skehan and Murray (in Skehan and others, 1979). Volcanic rocks similar to Diamond Hill Felsite crop out west of Lake Pearl, between Franklin and Wrentham, on west flank of Norfolk basin. These are shown within Wamsutta Formation on MA State bedrock map of Zen and others (1983) because of their proximity to Diamond Hill. They also resemble Proterozoic Z Mattapan Volcanic Complex. Chute (1966) described lenses of carbonate rock in red and green shale in Wamsutta in Norwood quad. Limestone also observed in rocks mapped as Wamsutta adjacent to exposed Dedham Granite at Manchester Pond Reservoir (J.P. Schafer, 1982, oral commun.). Red and green shales may actually be Cambrian. Upper member of Pondville Conglomerate grades into and interfingers with Wamsutta; in turn, Wamsutta interfingers with Rhode Island Formation in northwest part of Narragansett basin. Nonconformably overlies Dedham Granite. Partly equivalent to Rhode Island Formation. Age is Early and Middle Pennsylvanian. Contains a few plant fossils (Goldsmith, 1991).
Washington Gneiss (Proterozoic Y)
Washington Gneiss - Rusty-weathering, muscovite-biotite-sillimanite and/or kyanite-garnet schist; blue-quartz ribbed conglomerate, interlayered garnet-plagioclase-quartz metadacite.
Washington Gneiss (Proterozoic Y)
Washington Gneiss - Coarse- to medium-grained hornblende-garnet amphibolite, hornblende-plagioclase gneiss and phlogopite-hornblende-plagioclase amphibolite (metabasalt).
Westboro Formation (Proterozoic Z)
Westboro Formation - Quartzite, schist, calc-silicate quartzite, and amphibolite. Consists of quartzite and argillite in Saugus and Lynnfield areas. Westboro Formation consists primarily of orthoquartzite and subordinate mica schist, calc-silicate rock, amphibolite, and quartzitic biotite gneiss and schist. Westboro as portrayed by Nelson (1974), Bell and Alvord (1976), and Hepburn and DiNitto (1978) are correlative [with varying certainty]. West and south of Boston, disconnected masses of quartzite and associated rocks are shown on State bedrock map by Zen and others (1983) as Westboro although not continuous with belts mapped by Nelson (1974) or Hepburn and DiNitto (1978). Includes isolated quartzite masses mapped by Castle (1964) in Reading area. On State bedrock map, arbitrarily includes thin quartzite mapped as Burlington Formation by Bell and Alvord (1976) because the units are similar and to reduce number of small units on State map. Rocks mapped as Rice Gneiss by Nelson (1974) were included in unnamed metamorphosed mafic and felsic volcanic unit on State bedrock map, but author now feels it should be either a part of Westboro, or a separate unit below it. Westboro in Framingham area and to the northeast is overlain by unnamed assemblage of metamorphosed mafic and felsic volcanic rocks. South of town of Westborough, Westboro is truncated by Bloody Bluff-Lake Char fault system. Intruded by Proterozoic Z batholithic rocks. Equivalent to Plainfield Formation of eastern CT because it lies in same strike belt, and is probably equivalent to Quinnville Quartzite and unnamed mica schist and phyllite of Blackstone Group. Contact between Westboro and Blackstone is arbitrary on State bedrock map on basis of proximity of isolated exposures of the two units to their respective type areas. No area of continuous exposure exists between Westboro and Blackstone (Goldsmith, 1991).
Worcester Formation (Lower Devonian and Silurian)
Worcester Formation - Carbonaceous slate and phyllite and minor metagraywacke.
Maryland
Allegheny Formation and Pottsville Formation (Pennsylvanian)
Allegheny Formation - Interbedded sandstone, siltstone, claystone, shale, and coal beds; Upper Freeport coal at top; where present, Brookville coal defines base; thickness 275 feet in northeast, increases to 325 feet in south and west. And Pottsville Formation - Interbedded sandstone, siltstone, claystone, shale, and coal beds; conglomeratic orthoquartzite and protoquartzite at base; thickness 60 feet in northeast, increases to 440 feet in southwest
Baltimore Gabbro Complex (Late Precambrian (?) - Early Paleozoic )
Baltimore Gabbro Complex - Hypersthene gabbro with subordinate amounts of olivine gabbro, norite, anorthositic gabbro, and pyroxenite; igneous minerals and textures well preserved in some rocks, other rocks exhibit varying degrees of alteration and recrystallization with a new metamorphic mineral assemblage.
Baltimore Gneiss (Precambrian)
Baltimore Gneiss - Biotite-quartz-feldspar gneiss and biotite-hornblende gneiss; amphibolite widespread but subordinate; texturally varied; granitic gneiss, veined gneiss, augen gneiss, banded gneiss, and migmatite, in places complexly intermingled; age 1,1000 m.y. * by radiogenic dating. Layered paragneiss in Baltimore City southeast of Relay Quartz Diorite.
"Chemung" Formation, Parkhead Sandstone, Brallier Formation, and Harrell Shale (Devonian)
"Chemung" Formation - Predominantly marine beds characterized by gray to olive-green graywacke, siltstone, and shale; thickened ranges from 2,000 to 3,000 feet; Parkhead Sandstone - Gray to olive-green sandy shale, conglomeratic sandstone and graywacke; present in Washington County, identification uncertain in west; thickness averages 400 feet; Brallier Fomation - (Woodmont Shale of earlier reports). Medium to dark gray, laminated shale and siltstone; weathers to light olive-gray; grain size coarsens upward; thickness about 2,000 feet in west, about 1,7000 feet in east; and Harrell Shale - Dark gray laminated shale; absent in east where Brallier lies directly on Mahantango, Tully Limestone lies near base in west, in subsurface of Garrett County; total thickness in west 140 to 300 feet.
Chesapeake Group; Calvert Formation (Miocene)
Chesapeake Group; Calvert Formation - Plum Point Marls Member: Interbedded dark green to dark bluish-gray, fine-grained argillaceous sand and sandy clay; contains prominent shell beds and locally silica-cemented sandstones; and Fairhaven Member: Greenish-blue diatomaceous clay, weathers to pale gray; pale brown to white, fine-grained argillaceous sand; and greenish-blue sandy clay; total thickness 0 to 150 feet.
Chesapeake Group; Choptank Formation (Miocene)
Chesapeake Group; Choptank Formation - Interbedded brown to yellow very fine-grained to fine-grained sand and gray to dark bluish-green argillaceous silt; locally indurated to calcareous sandstone; prominent shell beds; thickness 0 to 50 feet.
Chilhowee Group; Harpers Formation (Cambrian)
Harpers Formation - Brown to dark bluish-gray banded shale, to light bluish-gray, finely laminated phyllite; distinctively pale purple in basal part; bedding obscured by cleavage; increasingly metamorphosed toward east from shale to slate and phyllite; estimated thickness 2,000 feet.
Chilhowee Group; Weverton Formation (Late Precambrian - Cambrian)
Weverton Formation - Interbedded white to dark gray, thin-bedded, micaceous, ferruginous, and sericitic quartzites, phyllites, and white, thick-bedded, ledge-making quartzites; some gray to brown ferruginous quartz conglomerate and purple-banded phyllite; thickness approximately 100 feet in south, increases to 425 feet in north.
Clinton Group, including Rochester Shale (Silurian)
Clinton Group, including Rochester Shale - Gray, thin-bedded calcareous shale and dark gray, thin- to medium-bed7 ded lenticular limestone; thickness 25 to 40 feet; Keefer Sandstone - White to yellowish-gray, thick-bedded protoquartzite and orthoquartzite; calcareous to west; thickness 10 feet in west, increases to 35 feet in east; and Rose Hill Formation - Olive-gray to drab, thin-bedded shale; some purple shale and gray, thin-bedded sandstone; including Cresaptown Iron Sandstone Member - Purple, hematite-cemented, quartzose sandstone; thickness 5 to 30 feet; occurs in lower half of formation; total thickness 300 feet in east, increases to 570 feet in west.
Cockeysville Marble (Late Precambrian (?))
Cockeysville Marble - Metadolomite, calc-schist, and calcite marble are predominant; calc-gneiss and calc-silicate marble widespread but minor; thickness about 750 feet.
Conemaugh Formation (Pennsylvanian)
Conemaugh Formation - Includes the rocks between the base of the Pittsburgh coal and the top of the Upper Freeport coal; consists of two unnamed members which are separated by the Barton coal; both members are gray and brown claystone, shale, siltstone and sandstone, with several coal beds; lower member also contains redbeds and fossiliferous marine shales; thickness 825 to 925 feet.
Conococheague Limestone (Upper Cambrian to Lower Ordovician )
Conococheague Limestone - Dark blue, laminated, oolitic, argillaceaous, and siliceous limestone, algal limestone, and flat-pebble conglomerate; siliceous shale partings; some sandstone and dolomite; thickness 1,600 to 1,900 feet.
Dunkard Group (Permian)
Dunkard Group - Red and green shale, siltstone, and sandstone, with thin lenticular beds of argillaceous limestone and thin beds of impure coal; thick-bedded, white conglomeratic sandstone at base; thickness greater than 200 feet; occurs only on hilltop
Elbrook Limestone (Cambrian)
Elbrook Limestone - Light blue, laminated, argillaceous limestone and calcareous shale; some dolomite; thickness 1,400 to possibly 3,000 feet.
Georgetown Mafic Complex (Late Precambrian (?) - Early Paleozoic )
Georgetown Mafic Complex - Poorly exposed complex of tonalite, dark quartz diorite, gabbro, amphibolite, and undifferentiated basic rocks.
Gettysburg Shale (Triassic)
Gettysburg Shale - Red shale and soft red sandstone and siltstone; estimated thickness less than 5,000 feet.
Greenbrier Formation (Mississippian)
Greenbrier Formation - Upper part red calcareous shale and sandstone interbedded with greenish-gray and reddish-gray argillaceous limestone; Loyalhanna Limestone Member: Gray to red, cross-bedded, arenaceous calcarenite; total thickness 200 to 300 feet.
Hamilton Group (including Mahantango Formation and Marcellus Shale), and including Tioga Metabentontite Bed, and Needmore Shale (Devonian)
Hamilton Group including Mahantango Formation - Dark gray, laminated shale, siltstone, and very fine-grained sandstone; thickness 600 feet in west, increases to 1,200 feet in east, and Marcellus Shale - Gray-black, thinly laminated, pyritic, carbonaceous shale; thickness 250 feet in east, increases to 500 feet in west. Also includes Tioga Metabentonite Bed - Brownish-gray, thinly laminated shale containing sand-size mica flakes; thickness less than one foot; and Needmore Shale - Olive-gray to black shale and dark, thin-bedded, fossiliferous, argillaceous limestone; thickness ranges from 70 to 145 feet.
Hampshire Formation (Devonian)
Hampshire Formation - Interbedded red shale, red mudstone, and red to brown cross-bedded siltstone and sandstone; some thin green shale; greenish-gray sandstone and shale toward top; fragmentary plant fossils; thickness 1,400 to 2,000 feet in west, increases to 3,800 feet in east.
Helderberg Formation and Keyser Limestone (Devonian)
Helderberg Formation, including Licking Creek Limestone Member - (Becraft Limestone of earlier reports.) Present only in east. Medium gray, medium-grained limestone near top; bedded black chert and thin-bedded limestone in middle; silty argillaceous limestone and shale near base; contains tongues of Shriver and Mandata; thickness 110 feet; Mandata Shale Member - Dark brown to black, thin-bedded shale; fossiliferous; thickness 20 to 30 feet in west, intertongues with Licking Creek Limestone Member in east; Corriganville Limestone Member (Head) - (New Scotland Limestone of earlier reports.) Medium gray, medium-grained, medium-bedded limestone, interbedded with chert; fossiliferous; thickness 15 to 30 feet; New Creek Limestone Member - (Coeymans Limestone of earlier reports.) Medium gray, thick-bedded, coarse-grained limestone; fossiliferous; thickness 9 to 10 feet. Limestone changes facies eastward into sandstone, the Elbow Ridge Sandstone Member - Medium-bedded, medium- to coarse-grained, calcarous sandstone; thickness 10 to 18 feet.; and the Keyser Limestone - Dark gray, thin- to thick-bedded, fine- to coarse-grained calcarenite; contains nodular limestone, dolomitic limestone, and calcarous shale; cherty near top; fossiliferous; thickness 200 to 300 feet.
Ijamsville Formation (Late Precambrian (?))
Ijamsville Formation - Blue, green, or purple phyllite and phyllitic slate, with interbedded metasiltstone and metagraywacke; flattened pumiceous blebs occur locally.
Ijamsville Formation and Marburg Schist (Late Precambrian (?))
Ijamsville Formation - Blue, green, or purple phyllite and phyllitic slate, with interbedded metasiltstone and metagraywacke; flattened pumiceous blebs occur locally; and Marburg Schist - Bluish-gray to silvery-green, fine-grained, muscovite-chlorite-albite-quartz schist; intensely cleaved and closely folded; contains interbedded quartzites.
James Run Gneiss (Late Precambrian (?))
James Run Gneiss - Thick-bedded, light gray biotite-quartz-plagioclase gneiss with thin interbeds of quartz amphibolite; grades downward into sharply layered, thin- to thick-bedded paragneiss composed of subequal amounts of biotite-quartz-plagioclase gneiss and quartz amphibolite; thickness unknown.
Juniata Formation (Ordovician)
Juniata Formation - Red to greenish-gray, thin- to thick-bedded siltstone, shale, subgraywacke, and protoquartzite; interbedded conglomerate; thickness 180 feet in east, increases to 500 feet in west.
Libertytown Metarhyolite (Late Precambrian (?))
Libertytown Metarhyolite - Purple, bluish-black, and red, dense, fine-grained metarhyolite with feldspar phenocrysts; interbedded with blue and purple amygdaloidal metaandesite; both rhyolite and andesite interbedded with blue, purple, and green phyllitic slates.
Lowland Deposits (Quaternary)
Lowland Deposits - Gravel, sand, silt, and clay. Medium- to coarse-grained sand and gravel; cobbles and boulders near base; commonly contains reworked Eocene glauconite; varicolored silts and clays; brown to dark gray lignitic silty clay; contains estuarine to marine fauna in some areas (includes in part Pamlico, Talbot, Wicomico and Sunderland Formations of earlier reports); thickness 0 to 150 feet.
Magothy Formation (Cretaceous)
Magothy Formation - Loose, white, cross-bedded, "sugary", lignitic sands and dark gray, laminated silty clays; white to orange-brown, iron-stained, subrounded quartzose gravels in western Anne Arundel County; absent in outcrop southwest of Patuxent River; thickness 0 to 60 feet.
Martinsburg Formation (Ordovician)
Martinsburg Formation - Upper part rhythmically interbedded graywackes, siltstones, and dark shales; lower part dark brown, dark gray, and black, thin-bedded fissile shale; thickness 2,000 to 2,500 feet.
Mauch Chunk Formation (Mississippian)
Mauch Chunk Formation - Red and green shale, reddish-purple mudstone, and red, green, brown, and gray thin-bedded and cross-bedded sandstones; thickness 500 feet in west, increases to about 800 feet in east.
McKenzie Formation (Silurian)
McKenzie Formation - Gray, thin-bedded shale and argillaceous limestone; interbedded red sandstone and shale in east; thickness 160 feet in western Washington County, increases to 300 feet in east and 380 feet in west.
Metarhyolite and Aasociated Pyroclastic Sediments (Late Precambrian)
Metarhyolite and Assoicated Pyroclastic Sediments - Metarhyolite - Dense, blue, cryptocrystalline, with white feldspar phenocrysts and glassy quartz; red porphyritic metarhyolite at contact with Catoctin Metabasalt; and Pyroclastic sediments - tuff breccia, blue slaty tuff, white tuffaceous sericitic schist, and banded green slate.
Monongahela Formation (Pennsylvanian)
Monongahela Formation - Interbedded claystone, argillaceous limestone, shale, sandstone, and coal beds; Waynesburg coal at top; Pittsburg coal at base; thickness 240 feet in west, increases to 375 feet in east.
New Oxford Formation (Triassic)
New Oxford Formation - Red, maroon, and gray sandstone, siltstone, and shale; basal conglomerate member: From vicinity of Maryland Rte. 73 and southward, limestone conglomerate with red and gray calcareous matrix; northward, quartz conglomerate with red sandy matrix; estimated total thickness 4,500 feet.
Oriskany Group including Ridgeley Sandstone and Shriver Chert (Devonian)
Oriskany Group, including Ridgeley Sandstone - White, medium- to coarse-grained, fossiliferous, calcareous orthoquartzite; thickness 160 feet in west. Medium to dark gray cherty, arenaceous limestone in east; thickness 50 feet; and Shriver Chert - Dark gray, brown, and black silty shales, cherty shales, and nodular and bedded black chert; fossiliferous; thickness 170 feet in west, upper boundary gradational with Ridgeley. Thickness 14 feet in east where the lower Shriver intertongues with the Licking Creek Limestone Member of the Helderberg Formation
Pocono Group, including the Purslane Sandstone and Rockwell Formation (Mississippian)
Pocono Group - Gray, white, tan, and brown, thin- to thick-bedded, cross-bedded sandstone, locally conglomeratic; interbedded gray and reddish-brown shale, mudstone, and siltstone; fragmentary plant fossils. Undifferentiated in Garrett and western Allegeny Counties. Includes Purslane Sandstone - White, thick-bedded, coarse-grained sandstone and conglomerate with thin coal beds and red shales. Eastern Allegany and Washington Counties. And also inlcudes Rockwell Formation - Coarse-grained arkosic sandstone, fine-grained conglomerate, and buff shale; dark shale with thin coal beds near base. Eastern Allegany and Washington Counties.
Port Deposit Gneiss (Paleozoic)
Port Deposit Gneiss - Moderately to strongly deformed intrusive complex composed of gneissic biotite quartz diorite, hornblende-biotite quartz diorite, and biotite granodiorite; all rocks foliated and some strongly sheared; age 550 +/- 50 m.y. * by radiogenic dating.
Potomac Group, including Raritan and Patapsco Formations, Arundel Clay, and Patuxent Formation (Cretaceous)
Potomac Group - Interbedded quartzose gravels; protoquartzitic to orthoquartzitic argillaceous sands; and white, dark gray, and multicolored silts and clays; thickness 0 to 800 feet. Includes Raritan and Patapsco Formations - Gray, brown, and red variegated silts and clays; lenticular, cross-bedded, argillaceous, subrounded sands; minor gravels; thickness 0 to 400 feet; Arundel Clay - Dark gray and maroon lignitic clays; abundant siderite concretions; present only in Baltimore-Washington area; thickness 0 to 100 feet; and Patuxent Formation - White or light gray to orange-brown, moderately sorted, cross-bedded, argillaceous, angular sands and subrounded quartz gravels; silts and clays subordinate, predominantly pale gray; thickness 0 to 250 feet.
Quaternary Deposits Undivided (Quaternary)
Quaternary Deposits Undivided - Undifferentiated gray to buff sand and gravel, gray to brown lignitic silt and clay, occasional boulders, and rare shell beds. Surficial deposits occur as intercalated fluvial sands and marsh muds (e.g. in upstream floodplain of the Wicomico and Nanticoke Rivers), well-sorted, stablized dune sands (e.g. eastern Wicomico County), shell-bearing estuarine clays and silts (e.g. lower Dorchester County) and Pocomoke River basin of Worcester County), and beach zone sands (e.g. Fenwick and Assateague Islands). Wisconsin to Holocene in age. Subsurface deposits of pre-Wisconsin age consist of buff to reddish-brown sand and gravel locally incised into Miocene sediments (e.g. Salisbury area), estuarine to marine white to gray sands, and gray to blue, shell-bearing clays (e.g. Worcester County).
Rockdale Run Formation (Ordovician)
Rockdale Run Formation - Upper one-third gray, mottled, cherty dolomite and dolomitic limestone; lower two-thirds gray, cherty argillaceous calcarenite and algal limestone with interbedded dolomite and oolitic limestone; thickness at least 1,700 feet east of Conococheague Creek, increases to about 2,500 feet in west.
Setters Formation (Late Precambrian (?))
Setters Formation - Upper member: Feldspathic mica schist and mica gneiss; total thickness 200 to 500 feet. Middle member: Impure quartzite interstratified with thin beds of mica schist; total thickness 200 to 500 feet. And Lower member: Medium-grained, feldspathic mica schist; locally granitized; total thickness 200 to 500 feet.
Stonehenge Limestone (Ordovician)
Stonehenge Limestone - Upper part gray, thin-bedded, coarse-grained to conglomeratic, oolitic calcarenite; some dolomite; lower part gray, thick-bedded, fine-grained algal limestone; thickness 500 to 800 feet.
Sugarloaf Mountain Quartzite (Late Precambrian (?))
Sugarloaf Mountain Quartzite - Massive white quartzite interbedded with softer sericitic quartzite, slate, and phyllite.
Swift Run Formation (Late Precambrian)
Swift Run Formation - Sericitic quartzite and phyllite; blue and green tuffaceous slate with sericitic blebs; some white marble with interbedded phyllite.
Tomstown Dolomite (Cambrian)
Tomstown Dolomite - Interbedded light gray to yellowish-gray, thin- to thick-bedded dolomite and limestone; some shale layers; gradational contact with Antietam; thickness 200 to 1,000 feet.
Tonoloway Limestone (Silurian)
Tonoloway Limestone - Gray, thin-bedded limestone, dolomitic limestone, and calcareous shale; thin sandstone member in east 20 feet above base; fossiliferous; thickness 400 feet in east, increases to 600 feet in west.
Ultramafic and Gabbroic Rocks (Early Paleozoic (?))
Ultramafic and Gabbroic Rocks - Mixed metagabbro, serpentinite, metapyroxenite, and actinolite-, chlorite-, and epidote-bearing schists.
Ultramafic Rocks (Early Paleozoic - Late Precambrian (?))
Ultramafic Rocks - Chiefly serpentinite with partly to completely altered dunite, peridotite, pyroxenite, and massive to schistose soapstone; talc-carbonate rock and altered gabbro are common in some bodies.
Upland Deposits (Eastern Shore) (Quaternary)
Upland Deposits (Eastern Shore) - Gravel, sand, silt, and clay. Mostly cross-bedded, poorly sorted, medium- to coarse-grained white to red sand and gravel; boulders near base; minor pink and yellow silts and clays; (Wicomico Formation of earlier reports); thickness 0 to 90 feet, locally thicker in paleochannels.
Upland Deposits (Western Shore) (Quaternary)
Upland Deposits (Western Shore) - Gravel and sand, commonly orange-brown, locally limonite-cemented; minor silt and red, white, or gray clay; (includes Brandywine, Bryn Mawr, and Sunderland Formations of earlier reports); lower gravel member and upper loam member in Southern Maryland; thickness 0 to 50 feet.
Urbana Formation (Late Precambrian (?))
Urbana Formation - Dark gray to green sericite-chlorite phyllite, metasiltstone, and quartzite; thin lenses of impure marble and calcareous phyllite occur locally.
Volcanic Complex of Cecil County (Late Precambrian (?))
Volcanic Complex of Cecil County - Metamorphosed andesitic and dacitic volcanic rocks (greenstone, greenschist, quartz amphibolite, and schistose felsite); amygdules and volcano-clastic textures locally preserved; thickness unknown.
Waynesboro Formation (Cambrian)
Waynesboro Formation - Upper part red, gray, and yellowish-brown, thin-bedded siltstone, shale, and ripple-marked, cross-bedded sandstone; lower part interbedded dark gray to red shale and thin-bedded dolomite; thickness approximately 600 feet.
Wills Creek Shale and Bloomsburg Formation (Silurian)
Wills Creek Shale - Olive to yellowish-gray, thin-bedded mudstone, calcareous shale, argillaceous limestone, and sandstone; thickness 450 feet in west, increases to 600 feet in east; and Bloomsburg Formation - Bright red, hematitic, thin- to thick-bedded sandstone and shale; some dark sandstone and green shale; Cedar Creek Limestone Member - Dark gray, fine- to medium-grained argillaceous limestone, occurs in middle part of formation; total thickness 20 feet in west, increases to 200 feet in east.
Maine
Cambrian gabbro/diorite/ultramafic rocks (Cambrian)
Cambrian gabbro/diorite/ultramafic rocks
Cambrian Jim Pond Formation (Cambrian)
Cambrian Jim Pond Formation
Carboniferous gabbro/diorite/ultramafic rocks (Carboniferous)
Carboniferous gabbro/diorite/ultramafic rocks undivided
Cretaceous gabbro/diorite/ultramafic rocks (Cretaceous)
Cretaceous gabbro/diorite/ultramafic rocks
Cretaceous quartz diorite - gabbro/diorite/ultramafic rocks (Cretaceous)
Cretaceous quartz diorite - gabbro/diorite/ultramafic rocks - Cretaceous biotite quartz diorite and gabbro/diorite/ultramafic rocks
Devonian Beck Pond Limestone (Devonian)
Devonian Beck Pond Limestone
Devonian Carrabassett Formation (Devonian)
Devonian Carrabassett Formation
Devonian gabbro/diorite/ultramafic rocks (Devonian)
Devonian gabbro/diorite/ultramafic rocks
Devonian gabbro/diorite/ultramafic rocks - quartz diorite (Devonian)
Devonian gabbro/diorite/ultramafic rocks - quartz diorite - Devonian gabbro/diorite/ultramafic rocks to biotite quartz diorite - gabbro, diorite, ultramafic rocks, biotite monzodiorite, biotite syenite, and biotite quartz diorite.
Devonian granite-quartz diorite (Devonian)
Devonian granite-quartz diorite: biotite granite, biotite granodiorite, biotite tonalite, biotite quartz syenite, biotite quartz monzodiorite, and biotite quartz diorite.
Devonian granite-quartz monzonite (hornblende accessory mineral) (Devonian)
Devonian granite-quartz monzonite (hornblende accessory mineral) Devonian hornblende-biotite granite to quartz monzonite- hornblende-biotite granite, hornblende-biotite granodiorite, hornblende-biotite tonalite, hornblende-biotite alkali feldspar quartz syenite, hornblende-biotite quartz syenite, and hornblende-biotite quartz monzonite.
Devonian granodiorite - quartz diorite (Devonian)
Devonian granodiorite - quartz diorite - Devonian biotite granodiorite to biotite quartz diorite - biotite granodiorite, biotite tonalite, biotite quartz syenite, biotite quartz monzodiorite, and biotite quartz diorite.
Devonian granodiorite - quartz monzodiorite (hornblende accessory mineral) (Devonian)
Devonian granodiorite - quartz monzodiorite (hornblende accessory mineral) - Devonian hornblende-biotite granodiorite to quartz monzodiorite - hornblende-biotite granodiorite, hornblende-biotite tonalite, hornblende-biotite quartz syenite, and hornblende-biotite quartz monzodiorite.
Devonian granodiorite - quartz syenite (porphyritic texture) (Devonian)
Devonian granodiorite - quartz syenite (porphyritic texture) - Devonian porphyritic biotite granodiorite to quartz syenite - porphyritic biotite granodiorite, porphyritic biotite tonalite, porphyritic alkali feldspar-biotite quartz syenite, and porphyritic biotite quartz syenite.
Devonian Hildreths Formation (Devonian)
Devonian Hildreths Formation
Devonian Littleton Formation (Devonian)
Devonian Littleton Formation
Devonian Matagamon Sandstone (Devonian)
Devonian Matagamon Sandstone
Devonian - Ordovician Bucksport Formation (Devonian - Ordovician)
Devonian - Ordovician Bucksport Formation
Devonian - Ordovician Flume Ridge Formation (Devonian - Ordovician)
Devonian - Ordovician Flume Ridge Formation
Devonian Seboomook Formation Temple Stream member (Silurian-Devonian)
Devonian Seboomook Formation Temple Stream member
Devonian - Silurian Allagash Lake Formation mixed sedimentary rocks (Devonian - Silurian)
Devonian - Silurian Allagash Lake Formation mixed sedimentary rocks
Devonian - Silurian Bar Harbor Formation (Devonian - Silurian)
Devonian - Silurian Bar Harbor Formation
Devonian - Silurian Fish River Lake Formation (Devonian - Silurian)
Devonian - Silurian Fish River Lake Formation
Devonian - Silurian Rindgemere Formation lower member (Devonian - Silurian)
Devonian - Silurian Rindgemere Formation lower member
Devonian - Silurian undifferentiated sedimentary rocks of the Spider Lake, Chandler Pond and Third Lake Formations (Devonian - Silurian)
Devonian - Silurian undifferentiated sedimentary rocks of the Spider Lake, Chandler Pond and Third Lake Formations
Devonian Tarratine Formation (Devonian)
Devonian Tarratine Formation
Devonian Tarratine Formation McKenny Pond Limestone (Devonian)
Devonian Tarratine Formation McKenny Pond Limestone
Devonian Tomhegan Formation (Devonian)
Devonian Tomhegan Formation
Devonian Trout Valley Formation (Devonian)
Devonian Trout Valley Formation
Mesozoic gabbro/diorite/ultramafic rocks (Mesozoic)
Mesozoic gabbro/diorite/ultramafic rocks
Ordovician Ammonoosuc Volcanics (Ordovician)
Ordovician Ammonoosuc Volcanics
Ordovician Benner Hill formation (Ordovician)
Ordovician Benner Hill formation
Ordovician - Cambrian Aziscohos Formation (Ordovician - Cambrian)
Ordovician - Cambrian Aziscohos Formation
Ordovician - Cambrian Chase Brook Formation (Ordovician - Cambrian)
Ordovician - Cambrian Chase Brook Formation
Ordovician - Cambrian Cookson formation (Ordovician - Cambrian)
Ordovician - Cambrian Cookson formation
Ordovician - Cambrian Dead River formation (Ordovician - Cambrian)
Ordovician - Cambrian Dead River formation
Ordovician - Cambrian Megunticook Formation (Ordovician - Cambrian)
Ordovician - Cambrian Megunticook Formation
Ordovician Chandler Ridge Formation (Ordovician)
Ordovician Chandler Ridge Formation
Ordovician Chase lake formation (Ordovician)
Ordovician Chase lake formation
Ordovician gabbro/diorite/ultramafic rocks (Ordovician)
Ordovician gabbro/diorite/ultramafic rocks
Ordovician Munsungun Lake Formation (Ordovician)
Ordovician Munsungun Lake Formation
Ordovician - Precambrian Z Cape Elizabeth Formation (Ordovician - Precambrian Z)
Ordovician - Precambrian Z Cape Elizabeth Formation
Ordovician Quimby formation (Ordovician)
Ordovician Quimby formation
Ordovician sandstone and pelite of the Depot Mountain sequence (Ordovician)
Ordovician sandstone and pelite of the Depot Mountain sequence
Ordovician Shin Brook Formation (Ordovician)
Ordovician Shin Brook Formation
Ordovician unnamed volcanic and sedimentary rocks (Ordovician)
Ordovician unnamed volcanic and sedimentary rocks
Penobscot Formation (Ordovician - Cambrian)
Penobscot Formation
Precambrian Z North Haven Formation (Precambrian)
Precambrian Z North Haven Formation
Precambrian Z rocks of Islesboro (Precambrian Z)
Precambrian Z rocks of Islesboro
Precambrian Z Rye Formation (Precambrian)
Precambrian Z Rye Formation
Silurian Ames Knob formation (Silurian)
Silurian Ames Knob formation
Silurian gabbro/diorite/ultramafic rocks (Silurian)
Silurian gabbro/diorite/ultramafic rocks
Silurian Hardwood Mountain Formation (Silurian)
Silurian Hardwood Mountain Formation
Silurian - Ordovician Aroostook River Formation (Silurian - Ordovician)
Silurian - Ordovician Aroostook River Formation
Silurian - Ordovician Carys Mills Formation (Silurian - Ordovician)
Silurian - Ordovician Carys Mills Formation
Silurian - Ordovician Lobster Lake Formation (Silurian - Ordovician)
Silurian - Ordovician Lobster Lake Formation
Silurian - Ordovician Vassalboro formation (Silurian - Ordovician)
Silurian - Ordovician Vassalboro formation
Silurian Perry Mountain formation (Silurian)
Silurian Perry Mountain formation
Silurian - Precambrian Z Berwick Formation (Silurian - Precambrian Z)
Silurian - Precambrian Z Berwick Formation
Silurian - Precambrian Z Eliot Formation (Silurian - Precambrian Z)
Silurian - Precambrian Z Eliot Formation
Silurian Rangeley Formation "A""member (Silurian)
Silurian Rangeley Formation "A" member
Silurian Rangeley Formation "B" member (Silurian)
Silurian Rangeley Formation "B" member"
Silurian Rangeley Formation "C" member (Silurian)
Silurian Rangeley Formation "C" member
Silurian rocks of the Fivemile Brook sequence (Silurian)
Silurian rocks of the Fivemile Brook sequence
Silurian Sangerville Formation (Silurian)
Silurian Sangerville Formation
Silurian Sangerville Formation limestone member (Silurian)
Silurian Sangerville Formation limestone member
Silurian Sangerville Formation Patch Mountain member (Silurian)
Silurian Sangerville Formation Patch Mountain member
Silurian Smalls Falls Formation (Silurian)
Silurian Smalls Falls Formation
Silurian Smalls Falls Formation? (Silurian)
Silurian Smalls Falls Formation?
Silurian Smyrna Mills Formation (Silurian)
Silurian Smyrna Mills Formation
Silurian Spragueville Formation (Silurian)
Silurian Spragueville Formation
Silurian undifferentiated pelites and sandstones (Silurian)
Silurian undifferentiated pelites and sandstones, in part of the Allsbury Formation and in part unnamed
Silurian unnamed sedimentary rocks (Silurian)
Silurian unnamed sedimentary rocks
Silurian unnamed volcanic and sedimentary rocks (Silurian)
Silurian unnamed volcanic and sedimentary rocks
Silurian Waterville Formation (Silurian)
Silurian Waterville Formation
Silurian Waterville Formation limestone member (Silurian)
Silurian Waterville Formation limestone member
Michigan
Baraga Group; Copps Formation (Early Proterozoic)
Baraga Group; Copps Formation - Fine- to medium-grained graywacke and less abundant gray to black slate. Thin basal conglomerate west of Lake Gogebic contains clasts of underlying Archean rocks in a quartzitic and argillaceous matrix.
Baraga Group; Tyler Formation (Early Proterozoic)
Baraga Group; Tyler Formation - Light- to dark-gray, feldspathic, fine-grained sandstone, argillaceous siltstone, and argillite. Near base, ferruginous argillite contains beds of cherty sideritic and pyritic iron-formation
Bass Island Dolomite (Late Silurian)
Bass Island Dolomite
Bayport Limestone (Mississippian)
Bayport Limestone
Cataract Formation (Early Silurian)
Cataract Formation
Chocolay Group, undivided (Early Proterozoic)
Chocolay Group, undivided - In Dickinson County, Mich., includes Randville Dolomite, Sturgeon Quartzite, and Fern Creek Formation. In Marquette range, between Marquette Bay and Champion, includes Wewe Slate, Kona Dolomite, Mesnard Quartzite, and Enchantment Lake Formation
Coldwater Shale (Mississippian)
Coldwater Shale
Copper Harbor Conglomerate (Middle Proterozoic)
Copper Harbor Conglomerate - Red lithic conglomerate and sandstone; mafic to felsic volcanic flows similar to those of the unnamed formation (unit Yu) are interlayered with the sedimentary rocks.
Dacite and volcanogenic graywacke (Early Proterozoic)
Dacite and volcanogenic graywacke - Includes andesite tuff. Occurs in northeastern Wisconsin. Dacite has age of 1866 +/- 39 Ma.
Detroit River Group (Middle Devonian)
Detroit River Group
Dickinson Group, undivided (Late Archean) (Late Archean)
Dickinson Group, undivided (Late Archean) - Metavolcanic and metasedimentary rocks in Dickinson County, Mich. From youngest to oldest, consists of Six-Mile Lake Amphibolite, Solberg Schist, and East Branch Arkose.
Ellsworth Shale (Late Devonian)
Ellsworth Shale
Gabbroic rocks of Keweenawan affinity (Middle Proterozoic)
Gabbroic rocks of Keweenawan affinity - gabbro, anorthosite, granite, peridotite
Granitic rocks (Early Proterozoic)
Granitic rocks - Gray to pinkish-gray, mottled, medium-grained syenite, granite, and granodiorite. Moderately strong propylitic alteration and weak cataclasis. Forms small bodies south of Crystal Falls, MI (James and others, 1968). A body near Tobin Location has a U-Pb concordia intercept age of 1840 +/-5 Ma (Z.E. Peterman, written communication, 1988). Includes porphyritic red granite that intrudes Lake Archean Dickinson Group - Red mylonitic gneissic granite (about 1970 Ma).
Jacobsville Sandstone (Middle Proterozoic)
Jacobsville Sandstone - Red, brown, and white quartzose sandstone, and minor siltstone, shale and conglomerate
Mafic metavolcanic rocks (Early Proterozoic)
Mafic metavolcanic rocks - Dominantly tholeiitic basalt and basaltic andesite flows and tuffs; associated with sheet dikes, massive and layered metagabbro, and ultramafic rocks. In northeastern Wisconsin, rocks have been named the Quinnesec Formation.
Menominee Group; Blair Creek Formation (Early Proterozoic)
Menominee Group; Blair Creek Formation - Dominantly dark-gray, massive, porphyritic tholeiitic basalt. Includes a basal conglomerate and a lean iron-formation in middle of formation
Menominee Group; Composite unit of Siamo Slate and Ajibik Quartzite (Early Proterozoic)
Menominee Group; Composite unit of Siamo Slate and Ajibik Quartzite - Siamo Slate is laminated green siltstone and argillite. Ajibik Quartzite is white, buff, and pink orthoquartzite and less abundant sericite quartzite.
Menominee Group; Hemlock Formation (Early Proterozoic)
Menominee Group; Hemlock Formation - Predominantly mafic to intermediate volcanic flows and pyroclastic rocks with interlayered slate and tuff beds
Menominee Group, undivided (Early Proterozoic)
Menominee Group, undivided - Includes Negaunee Iron-formation, Siamo Slate, and Ajibik Quartzite in areas where units are too thin to map individually.
Metabasalt (Late Archean) (Late Archean)
Metabasalt (Late Archean) - Derived from mafic to intermediate pyroclastic rocks and massive to pillowed lava flows. Unit mapped as Ramsey Formation by Prinz (1981) south of Gogebic Range; mapped as Mona Schist and Kitchi Schist in northern complex of Marquette District.
Metagabbro (Early Proterozoic)
Metagabbro - Mafic to ultramafic bodies defined and delineated principally by positive magnetic and gravity anomalies; includes diorite bodies. Comagmatic with unit Xmi
Michigan Formation (Mississippian)
Michigan Formation
Migmatitic gneiss and amphibolite (Late to Early Archean) (Archean)
Migmatitic gneiss and amphibolite (Late to Early Archean) - Varied gneisses of mostly unknown age in cores of gneiss domes and fault-bounded uplifts (Archean gneiss terranes). Except for the Watersmeet dome (Late to Early Archean), all dated rocks are Late Archean. Includes granite of Late Archean age that transgresses gneisses and amphibolite.
Munising Formation (Late Cambrian)
Munising Formation
Oronto Group; Freda Sandstone (Middle Proterozoic)
Oronto Group; Freda Sandstone - Mainly reddish-brown, medium- to fine-grained lithic arkosic sandstone, siltstone, and micaceous silty shale.
Oronto Group; Nonesuch Shale (Middle Proterozoic)
Oronto Group; Nonesuch Shale - Gray, green, and brown lithic siltstone, shale, and sandstone. Copper sulfides and native copper occur locally near base
Paint River Group; Lower part (Early Proterozoic)
Paint River Group; Lower part - Includes Stambaugh Formation, Hiawatha Graywacke, Riverton Iron-formation, and Dunn Creek Slate (James and others, 1968). Correlated with lower part of Baraga Group
Paleozoic undivided (Paleozoic)
Paleozoic undivided
Peavy Pond complex (Early Proterozoic)
Peavy Pond complex - Chiefly hornblende metagabbro, but includes metanorite, metatonalite, granodiorite, and granite (Bayley, 1959).
Porcupine Volcanics (Middle Proterozoic)
Porcupine Volcanics - Generally dark-gray basalt, andesite, and felsite flows and subordinate interflow sedimentary rocks
Portage Lake Volcanics (Middle Proterozoic)
Portage Lake Volcanics - Lava flows, mostly basalt, andesite and felsite flows and subordinate interflow sedimentary rocks.
Powder Mill Group; Kallander Creek Volcanics (Middle Proterozoic)
Powder Mill Group; Kallander Creek Volcanics - Basalt, andesite and lesser rhyolite flows. Basalt flows near base of the formation contain plagioclase phenocrysts, some in radiating clusters
Prairie du Chien Group (Early Ordovician)
Prairie du Chien Group
Saginaw Formation (Pennsylvanian)
Saginaw Formation
Salina Group (Late Silurian)
Salina Group
Trempealeau Formation (Late Cambrian)
Trempealeau Formation
Trenton Limestone (Late Ordovician)
Trenton Limestone
Minnesota
Animikie Group; Iron-formation - Iron-formation (Early Proterozoic)
Animikie Group; Iron-formation - Includes the Gunflint Iron Formation in Cook County and the Biwabik Iron Formation and subjacent units of arenite and conglomerate assigned to the Pokegama Quartzite in Itasca, St. Louis, and Lake Counties. Also includes thin lenses of iron-formation (Remer Member) in the Virginia Formation in Itasca County.
Animikie Group; Shale, siltstone, feldspathic graywacke, and associated volcaniclastic rocks (Early Proterozoic)
Animikie Group; Shale, siltstone, feldspathic graywacke, and associated volcaniclastic rocks - Includes the Rove Formation in Cook County, the Virginia Formation in St. Louis, Itasca, and Lake Counties, and the Thomson Formation in Carlton County
Chengwatana Volcanic Group (Middle Proterozoic)
Chengwatana Volcanic Group - Basalt and related volcanogenic and interflow sedimentary rocks in east-central Minnesota
Coleraine Formation (Cretaceous)
Coleraine Formation - Jasper-pebble conglomerate, sandstone, and shale of diverse origin on the Mesabi range of northern Minnesota, and unnamed sandstone and shale of nonmarine to marine origin in east-central Minnesota
Cretaceous rocks, undivided (Cretaceous)
Cretaceous rocks, undivided - Dakota, Graneros, Greenhorn, Carlie, Niobara, and Pierre formations and their nonmarine equivalents in northwestern, southwestern, and southeastern Minnesota
Denham Formation (Early Proterozoic)
Denham Formation - Quartz arenite and siltstone, oxide iron-formation, marble, mafic hypabyssal intrusions and fragmental volcanic rocks metamorphosed to the staurolite grade of the amphibolite facies
Felsic to intermediate volcanic and volcaniclastic rocks, mica schist, phyllite, and granitoid rocks (Late Archean)
Felsic to intermediate volcanic and volcaniclastic rocks, mica schist, phyllite, and granitoid rocks - Variably and cataclastically deformed. Unit forms aeromagnetic "quiet zone" and probably contains some rocks of Paleoproterozoic age.
Fond du Lac Formation (Middle Proterozoic)
Fond du Lac Formation - Red to dark-brown shale, feldspathic sandstone, and arkose of fluvial origin. Includes the Oldenberg Point Member, a pronounced basal unit of quartz-pebble conglomerate in the Duluth area.
Gabbro, diorite, peridotite, and associated komatiitic flows of the Deer Lake sequence in Itasca County and the upper part of the Newton Lake Formation in Lake and St. Louis Counties (Late Archean)
Gabbro, diorite, peridotite, and associated komatiitic flows of the Deer Lake sequence in Itasca County and the upper part of the Newton Lake Formation in Lake and St. Louis Counties
Granite-rich migmatite (Late Archean)
Granite-rich migmatite - Granitic gneiss, paragneiss, schist, and migmatite in the Vermillion Granitic Complex, and other parts of extreme northern Minnesota. Grades into granitoid rocks.
Jurassic rocks, undivided (Jurassic)
Jurassic rocks, undivided - Unnamed units of green, gray, brown, and red shale, white to tan micritic limestone and dolostone, and white, fine- to coarse-grained sandstone and siltstone; unit contains nodules of chert and gypsum
Lithograph City Formation, Coralville Formation and Hinckle and Eagle City Members of the Little Cedar Formation (Cedar Valley Group), undivided (Devonian)
Lithograph City Formation, Coralville Formation and Hinckle and Eagle City Members of the Little Cedar Formation (Cedar Valley Group), undivided - Limestone, dolostone, and lesser amounts of shale
Little Falls Formation; Quartz-rich slate, argillite, and schist in the northwestward extent of the unit and coarse-grained megacrystic garnet-staurolite-schist in the southwestward extent (Early Proterozoic)
Little Falls Formation; Quartz-rich slate, argillite, and schist in the northwestward extent of the unit and coarse-grained megacrystic garnet-staurolite-schist in the southwestward extent - Unit as an uncertain stratigraphic position relative to other Paleoproterozoic stratified units but is apparently younger than the Mille Lacs and North Range Groups.
Logan Intrusions (Middle Proterozoic)
Logan Intrusions - Diabase, porphyritic diabase, gabbro, and related felsic sills and dikes.
Lower Ordovician rocks, undivided (Lower Ordovician)
Lower Ordovician rocks, undivided - Shakopee and Oneota Formations of the Prairie du Chien Group in the Hollandale embayment of southeastern Minnesota. Unit consists dominantly of dolostone and dolomitic limestone. The Shakopee also contains intervals of quartz arenite, including a pronounced basal unit named the New Richmond Member
Mafic metavolcanic rocks (Late Archean)
Mafic metavolcanic rocks - Dominantly basalt that contains thin sedimentary units, including iron-formation. Includes parts of the Ely Greenstone and the Newton Lake Formation in northeastern Minnesota. Also includes metabasalt exposed in the Minnesota River Valley.
Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower greenschist facies (Early Proterozoic)
Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower greenschist facies - Includes fragmental volcanic rocks, mafic hypabyssal intrusions, graywacke, graphitic argillite and oxide iron-formation
Metasedimentary rocks, undivided (Late Archean)
Metasedimentary rocks, undivided - Graywacke, slate, local units of conglomerate, arenite, graphitic slate, fine-grained felsic volcanogenic, and volcaniclastic rocks, lean oxide iron-formation and its metamorphic equivalents. Includes the Knife Lake Group and the Lake Vermilion Formation in northeastern Minnesota.
Middle Ordovician rocks, undivided (Middle Ordovician)
Middle Ordovician rocks, undivided - Decorah Shale; limestone of the Platteville Formation; shaly rocks of the Glenwood Formation; and St. Peter Sandstone in the Hollandale embayment of southeastern Minnesota
Migmatitic gneiss, amphibolite, and granite (Middle to Early Archean)
Migmatitic gneiss, amphibolite, and granite - Montevideo and Morton Gneisses (3600-3000 m.y.) in the Minnesota River Valley, southwestern Minnesota; McGrath Gneiss (2750 m.y.) east of Mille Lacs Lake; components of Hillman Migmatite southwest of Mille Lacs Lake; and Sartell Gneiss in Stearns County. Inferred to include various younger rocks, including granitoid intrusions in the Hillman Migmatite and pillowed basalt in poorly exposed areas of southwestern Minnesota.
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Graphitic schist, slate, and silicate iron-formation metamorphosed to the lower greenschist facies and related conditions (Early Proterozoic)
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Graphitic schist, slate, and silicate iron-formation metamorphosed to the lower greenschist facies and related conditions - Includes substantial quantities of mafic to intermediate igneous rocks
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower amphibolite facies (Early Proterozoic)
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower amphibolite facies - Includes fragmental volcanic rocks, mafic hypabyssal intrusions, graphitic argillite, and oxide iron-formation
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Quartz arenite, siltstone, and chert-rich dolostone of the Trout Lake Formation in Crow Wing County (Early Proterozoic)
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Quartz arenite, siltstone, and chert-rich dolostone of the Trout Lake Formation in Crow Wing County
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Quartzite at Dam Lake (Early Proterozoic)
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Quartzite at Dam Lake - Quartz arenite and sericitic quartz schist; includes a substantial component of mafic volcanic rock fragments
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Slate, argillite, and metasiltstone metamorphosed to the lower greenschist facies (Early Proterozoic)
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Slate, argillite, and metasiltstone metamorphosed to the lower greenschist facies - Includes lesser amounts of mafic hypabyssal intrusions, and fragmental mafic volcanic rocks
Mille Lacs Group and related rocks of the Penokean fold-and-thrust bets; Graphitic schist, phyllite and slate interbedded on a fine scale (Early Proterozoic)
Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Graphitic schist, phyllite and slate interbedded on a fine scale
Mixed metavolcanic rocks (Late Archean)
Mixed metavolcanic rocks - Mafic to felsic volcanic sequences that have variable amounts of felsic volcanogenic and volcaniclastic rocks and lean iron-formation. Includes parts of the Ely Greenstone and the Soudan Iron-formation in northeastern Minnesota.
Multiphase intrusions of hornblende-pyroxene-bearing and biotite-bearing monzonite, monzodiorite, diorite, syenite, and granodiorite (Late Archean)
Multiphase intrusions of hornblende-pyroxene-bearing and biotite-bearing monzonite, monzodiorite, diorite, syenite, and granodiorite - Typically postdates regional metamorphism and deformation associated with the Algoman orogen.
North Range Group; Mahnomen Formation (Early Proterozoic)
North Range Group; Mahnomen Formation - Claystone, shale, siltstone, and graywacke metamorphosed to the greenschist facies
North Range Group; Rabbit Lake Formation (Early Proterozoic)
North Range Group; Rabbit Lake Formation - Mudstone, graywacke, iron-rich strata, and associated mafic metavolcanic rocks metamorphosed to the greenschist facies. Includes thin beds of carbonate-silicate iron-formation
North Shore Volcanic Group; Normally polarized volcanic rocks, undivided (Middle Proterozoic)
North Shore Volcanic Group; Normally polarized volcanic rocks, undivided - Basalt, andesitic basalt, rhyolite and related volcanogenic interflow sedimentary rocks along and inland from the North Shore of Lake Superior.
North Shore Volcanic Group; Reversely polarized volcanic rocks, undivided (Middle Proterozoic)
North Shore Volcanic Group; Reversely polarized volcanic rocks, undivided - Mixed tholeiitic diabasic and porphyritic basalt, trachybasalt, and rhyolite in far northeastern Minnesota and porphyritic and diabasic basalt near Duluth. Includes units of a basal quartz arenite, Puckwunge Sandstone and Nopeming Formation, in northeastern Minnesota and near Duluth, respectively.
Paragneiss, schist, and amphibolite (Late Archean)
Paragneiss, schist, and amphibolite - Amphibolite-facies equivalent of units Amv and Ams; locally includes abundant intrusions of unit Agr.
Pokegama Quartzite (Early Proterozoic)
Pokegama Quartzite - Quartz arenite, siltstone, and shale. Shown only in Crow Wing County.
Post-tectonic intrusions of the Penokean orogen (Early Proterozoic)
Post-tectonic intrusions of the Penokean orogen - Small stocks of olivine pyroxenite in Morrison County; small plutons of hornblende-rich diorite and gabbro that contain layers and lenses of nelsonite, pyroxenite, and anorthosite in Todd County.
Post-tectonic mafic intrusions (Late Archean)
Post-tectonic mafic intrusions - Gabbro, peridotite, pyroxenite, and their metamorphic equivalents. Unit also includes small intrusive complexes of anorthosite, gabbroic anorthosite, and anorthositic gabbro. Generally characterized by pronounced magnetic signatures.
Sioux Quartzite (Early Proterozoic)
Sioux Quartzite - Red quartzite of fluvial to possibly marginally marine origin. Includes quartz-pebble conglomerate, claystone (catlinite, also called pipestone), a basal (rhyolite) pebble conglomerate in Pipestone County, and a basal (granite, quartz, chert, iron-formation) conglomerate in Nicollet County on the Minnesota River
Solor Church Formation (Middle Proterozoic)
Solor Church Formation - Dark-red to dark-brown shale, siltstone, and lithic sandstone of fluvial origin in Scott and Carver Counties; metamorphosed to zeolite facies
Syntectonic intrusions of the Penokean orogen (Early Proterozoic)
Syntectonic intrusions of the Penokean orogen - Includes the Pierz Granite, the Freedhem and Bradbury Creek Granodiorites, and several unnamed intrusions of granite, granodiorite, tonalite, and gabbro in east-central Minnesota
Syntectonic to pretectonic granitoid rocks (Late Archean)
Syntectonic to pretectonic granitoid rocks - Granite and granodiorite of the Vermilion Granitic Complex, the Giants Range and Bemidji batholiths, as well as smaller intrusions of tonalite and monzonite of the Algoman orogen in northern Minnesota. Also includes the Odessa, Sacred Heart, and Fort Ridgely Granites exposed along the Minnesota River Valley in southwestern Minnesota.
Unnamed schistose, volcanic, and hypabyssal rocks of mafic composition and volcanic, volcaniclastic, and intrusive rocks of felsic composition (Early Proterozoic)
Unnamed schistose, volcanic, and hypabyssal rocks of mafic composition and volcanic, volcaniclastic, and intrusive rocks of felsic composition - May be correlative with rocks of the Wisconsin magmatic terranes.
Upper Cambrian, undivided (Late Cambrian)
Upper Cambrian, undivided - Jordan Sandstone; dolomite, glauconite, and silty glauconite rocks of the St. Lawerence and Franconia Formation; Ironton and Galesville Sandstones; sandy and shaly rocks of the Eau Claire Formation; and the Mt. Simon Sandstone.
Missouri
CHEROKEE GROUP- Cabaniss Subgroup, Krebs Subgroup (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Middle Desmonian])
CHEROKEE GROUP - Cabaniss Subgroup - cyclic deposits, shale, sandstone, clay and several workable coal beds. Krebs Subgroup - cyclic deposits, sandstone, siltstone, shale, clay and some workable coal beds
CHESTERIAN SERIES (Phanerozoic | Paleozoic | Carboniferous Mississippian-Late [Chesterian])
CHESTERIAN SERIES - FAYETTEVILLE FORMATION, BATESVILLE FORMATION, HINDVILLE LIMESTONE, VIENNA LIMESTONE, TAR SPRINGS SANDSTONE, GLEN DEAN FORMATION, HARDINSBURG FORMATION, GOLCONDA FORMATION, CYPRESS FORMATION, PAINT CREEK FORMATION, YANKEETOWN SANDSTONE, RENAULT FORMATION, AUX VASES SANDSTONE, STE. GENEVIEVE LIMESTONE
DEVONIAN SYSTEM (Phanerozoic | Paleozoic | Devonian-Early Devonian-Middle(?) Devonian-Late)
DEVONIAN SYSTEM - CHATTANOOGA SHALE, SYLAMORE SANDSTONE, FORTUNE FORMATION, HOLTS SUMMIT SANDSTONE, SNYDER CREEK SHALE, CEDAR VALLEY LIMESTONE, LOUISIANA LIMESTONE, SAVERTON SHALE, GRASSY CREEK SHALE, TURPIN SANDSTONE, BUSHBERG SANDSTONE, GLEN PARK LIMESTONE, St. LARENT LIMESTONE, BEAUVAIS SANDSTONE, GRAND TOWER LIMESTONE, CLEAR CREEK CHERT, LITTLE SALINE LIMESTONE, GRASSY KNOB CHERT, BAILEY FORMATION
DOUGLAS GROUP (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Upper Virgilian])
DOUGLAS GROUP - cyclic deposits, dominantly shale with sandstone, and limestone.
ELVINS GROUP- (INCLUDING DERBY-DOERUN DOLOMITE, DAVIS FORMATION), BONNETERRE DOLOMITE (Phanerozoic | Paleozoic | Cambrian-Furongian [Croixian])
ELVINS GROUP - (INCLUDING DERBY - DOERUN DOLOMITE - alternating thin dolomite, siltstone, and shale; DAVIS FORMATION - glauconitic shale with fine - grained sandstone, limestone, and dolomite); BONNETERRE DOLOMITE - dolomite, dolomitic limestone, and limestone; glauconitic in lower part
GULFIAN SERIES (Phanerozoic | Mesozoic | Cretaceous-Late [Gulfian])
GULFIAN SERIES - Owl Creek Formation - massive, sandy, micaceous, fossilliferous, glauconitic marine clay, max 100 ft. McNairy Formation - unconsolidated sandstone with clay and gravel lenses, max of 250 ft.
HOLOCENE SERIES (Phanerozoic | Cenozoic | Quaternary | Holocene)
HOLOCENE SERIES - Alluvium - clay, silt, sand, and gravel
JOACHIM DOLOMITE, DUTCHTOWN FORMATION (Phanerozoic | Paleozoic | Ordovician-Middle [Mohawkian])
JOACHIM DOLOMITE, DUTCHTOWN FORMATION
KANSAS CITY GROUP (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Upper Missourian])
KANSAS CITY GROUP - cyclic deposits, limestone and shale with minor sandstone and coal.
KINDERHOOKIAN SERIES (Phanerozoic | Paleozoic | Carboniferous Mississippian-Early [Kinderhookian])
KINDERHOOKIAN SERIES - NORTHVIEW SHALE, SEDALIA FORMATION, COMPTON LIMESTONE, BACHELOR FORMATION CHOUTEAU GROUP, HANNIBAL SHALE, HORTON CREEK LIMESTONE
LANSING GROUP (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Upper Missourian])
LANSING GROUP - cyclic deposits of limestone and shale
LEEMON FORMATION, MAQUOKETA GROUP, CAPE LIMESTONE, KIMMSWICK LIMESTONE, NOIX-CYRENE LIMESTONE, MAQUOKETA SHALE (Phanerozoic | Paleozoic | Ordovician-Middle Ordovician-Late)
LEEMON FORMATION, MAQUOKETA GROUP INCLUDING: (GIRARDEAU LIMESTONE, ORCHARD CREEK SHALE, THEBES SANDSTONE, CAPE La CROIX SHALE), CAPE LIMESTONE, KIMMSWICK LIMESTONE, NOIX - CYRENE LIMESTONE, MAQUOKETA SHALE
MARMATON GROUP (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Middle Desmonian])
MARMATON GROUP - cyclic deposits, shale and limestone with sandstone, clay and several coal beds, some workable
OSAGEAN SERIES (Phanerozoic | Paleozoic | Carboniferous Mississippian-Early [Osagean])
OSAGEAN SERIES - KEOKUK LIMESTONE, BURLINGTON LIMESTONE, ELSEY FORMATION, REEDS SPRING FORMATION, PIERSON LIMESTONE, FERN GLEN FORMATION
PENNSYLVANIAN UNDIFFERENTIATED (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
PENNSYLVANIAN UNDIFFERENTIATED
PLEASANTON GROUP (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Upper Missourian])
PLEASANTON GROUP - dominantly shale and sandstone with minor coal.
PLEISTOCENE SERIES (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
PLEISTOCENE SERIES - Loess, till, drift, clay, silt, sand and gravel (shown on cross section, not on map)
RIVERTON FORMATION, BURGNER FORMATION (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Atokan])
RIVERTON FORMATION - shale, clay, coal. BURGNER FORMATION - limestone
ROUBIDOUX FORMATION (Phanerozoic | Paleozoic | Ordovician-Early [Ibexian])
ROUBIDOUX FORMATION - sandstone, chert and interbedded dolomite
SHAWNEE GROUP (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Upper Virgilian])
SHAWNEE GROUP - cyclic deposits, limestone and shale with sandstone and siltstone.
SILURIAN SYSTEM (Phanerozoic | Paleozoic | Silurian-Early Silurian-Middle(?) Silurian-Late)
SILURIAN SYSTEM - JOLIET LIMESTONE, BOWLING GREEN DOLOMITE, BRYANT KNOB FORMATION, BAINBRIDGE FORMATION, SEXTON CREEK LIMESTONE
SMITHVILLE DOLOMITE, POWELL DOLOMITE, COTTER DOLOMITE, JEFFERSON CITY DOLOMITE (Phanerozoic | Paleozoic | Ordovician-Early [Ibexian])
SMITHVILLE DOLOMITE, POWELL DOLOMITE, COTTER DOLOMITE, JEFFERSON CITY DOLOMITE - fine crystalline, silty, cherty dolomite, and oolitic chert with local sandstone beds
ST. PETER SANDSTONE, EVERTON FORMATION (Phanerozoic | Paleozoic | Ordovician-Early Ordovician-Middle)
ST. PETER SANDSTONE, EVERTON FORMATION
TERTIARY SYSTEM (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene(?) Oligocene(?) Miocene(?) Pliocene-Early(?) Pliocene-Middle(?) Pliocene-Late)
TERTIARY SYSTEM - PLIOCENE SERIES - Mounds Gravel (Lafayette Formation) - ferruginous, chert gravel, max of 60 ft. EOCENE SERIES - Wilcox Group - includes Holly Springs Formation - x - bedded sandstone, clay and gravel, max of 1200 ft.; Ackerman Formation - clay with lens of sand and gravel, max of 100ft. PALEOCENE SERIES - Midway Group - includes Porters Creek Clay - bentonitic clay, max of 200 ft.; Clayton Formation - marl, fossiliferous, calcareous, limonitic, glauconitic sand and clay, max of 20 ft.,
UNDIFFERENTIATED (Phanerozoic | Paleozoic | Ordovician)
UNDIFFERENTIATED (ORDOVICIAN ROCKS)
WABAUNSEE GROUP (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Upper Virgilian])
WABAUNSEE GROUP - cyclic deposits, principally shale, sitlstone, sandstone with thin limestone beds and minor coal
Mississippi
Catahoula formation (Miocene)
Catahoula formation - Irregularly bedded gray sand and sandstone; mottled red and gray, green, and chocolate-colored clay; some quartzite, and some gravel; the Paynes Hammock sand, sandy limestone cross-bedded fine green sand, and thin-bedded sand and clay, is mapped with the underlying Chickasawhay limestone in eastern MS.
Chester group (Mississippian)
Chester group - Limestone, chert, and shale of Meramec, Osage, and Kinderhook age.
Chester group (Mississippian)
Chester group - Sandstone, shale, and limestone.
Citronelle formation (Pleistocene)
Citronelle formation - Red sand and gravel and white clay; may be of Pliocene age; the formation mapped is equivalent to the Willis sand and does not include the terrace deposits, colluvium, and residuum commonly considered "Citronelle".
Clayton formation (Paleocene)
Clayton formation - (Midway group), Upper part, greenish-gray coarsely glauconitic sandy clay and marl; lower part, crystalline sandy limestone and loose sand, represented south of Houston by a discontinuous bed of indurated calcareous sandstone.
Coastal deposits (Holocene)
Coastal deposits - Loam, sand, gravel and clay.
Cockfield (Eocene)
Cockfield - (Claiborne group), Irregularly bedded, more or less laminated liginitic clay, sand, and lignite; sparingly glauconitic.
Coffee sand (Upper Cretaceous)
Coffee sand - (Selma group), Light-gray cross-bedded to massive glauconitic sand and sandy clay and calcareous sandstone.
Cook Mountain formation (Eocene)
Cook Mountain formation - (Claiborne group), Southeast of Pearl River, marl, limestone, glauconitic sand, and chocolate-colored clay; northwest of Pearl River, predominantly chocolate-colored clay with some glauconitic sand.
Eutaw formation (Upper Cretaceous)
Eutaw formation - More or less cross-bedded and thinly laminated glauconitic sand and clay; basal part includes the McShan formation, greenish-gray, micaceous, locally very glauconitic, very fine-grained sand and thin-bedded light-gray clay, small chert gravels may be present in basal beds, not recognized in northern Tishomingo County.
Forest Hill formation and Red Bluff clay (Oligocene)
Forest Hill formation and Red Bluff clay - Forest Hill sand, cross-bedded fine gray sand, laminated fine sand and clay, and a little lignite; in Wayne and Clarke Counties lower part merges eastward into Red Bluff clay, blue-green glauconitic, gypsiferous, fossiliferous clay and thin limestone beds.
Kosciusko formation (Eocene)
Kosciusko formation - (Claiborne group), irregularly bedded sand, clay, and some quartzite.
Pascagoula and Hattiesburg formation (Miocene)
Pascagoula and Hattiesburg formation - Green and bluish-green clay, sandy clay, and sand; gray siltstone and sand; locally fossiliferous.
Prairie Bluff chalk and Owl Creek formation (Upper Cretaceous)
Prairie Bluff chalk and Owl Creek formation - (Selma group), Prairie Bluff chalk, compact brittle chalk, sandy chalk, and calcareous clay; at base contains many phosphatic molds of fossils; in Ponotoc and Union Counties merges northward into Owl Creek formation, tough blue glauconitic sandy clay.
Ripley formation (Upper Cretaceous)
Ripley formation - (Selma group), gray to greenish-gray fine glauconitic sand, clay, and sandy limestone; south of Oktibbeha County is very sandy micaceous chalk.
Tallahatta formation and Neshoba sand (Eocene)
Tallahatta formation and Neshoba sand - (Claiborne group), Southeast of Pearl River predominantly more or less glauconitic claystone and clay with lenses of sand and some sandstone; highly cross-bedded sand at base; northwest of Pearl river predominantly sand, locally glauconitic, containing claystone and clay lenses and abundant clay stringers; Neshoba sand, sparingly glauconitic fairly coarse sand not recognized southeast of Newton County or north of Yalobusha River.
Tuscaloosa formation (Upper Cretaceous)
Tuscaloosa formation - Light and vari-colored irregularly bedded sand, clay, and gravel; gravel is mostly in lower portion.
Vicksburg group and Chickasawhay limestone (Oligocene)
Vicksburg group and Chickasawhay limestone - Chickasawhay limestone, sandy limestone, and sand, present only in eastern MS (mapped with it is the overlying Paynes Hammock sand of Miocene age); Vicksburg group, predominantly limestone and marl, but contains some bentonite and near the top, chocolate-colored clay and some sand.
Wilcox formation (Eocene)
Wilcox formation - Irregularly bedded fine to coarse sand, more or less lignitic clay and lignite; includes bauxite bearing Fearn Springs sand member at base.
Montana
Alluvium (Phanerozoic | Cenozoic | Quaternary)
Alluvium: mainly valley fill consisting of silt, sand, and gravel; includes some terrace deposits and glacial drift of Pleistocene age in some areas; locally includes hot spring tufa. The older part of the alluvium, where present, is probably of Pliocene age.
Altyn limestone (Proterozoic | Mesoproterozoic)
Altyn limestone: dominantly dolomite and magnesian limestone that weathers to a distinctive yellowish brown; some feldspathic quartzite and conglomerate. Correlation with the Ravalli group is provisional.
Arikaree formation (Phanerozoic | Cenozoic | Tertiary)
Arikaree formation: gray sandstone with layers of concretions; contains volcanic ash and, locally, channels filled with conglomerate; known only in southeastern Montana.
Bearpaw shale (Phanerozoic | Mesozoic | Cretaceous-Late)
Bearpaw shale: Dark-gray and brownish clay shale; thick units of nonfissile bentonitic shale; calcareous and ferruginous concretions throughout; contains some thick bentonite beds.
Belle Fourche shale (Phanerozoic | Mesozoic | Cretaceous-Late)
Belle Fourche shale: dark blue-gray siliceous shale with many calcareous and ferruginous concretions and intercalated thin layers of bentonite.
Boulder batholith and broadly related stocks (Phanerozoic | Cenozoic | Tertiary Cretaceous)
Boulder batholith and broadly related stocks: mainly quartz monzonite, but includes diorite, aplite, and other rocks. The distinctions between masses relative to the Boulder batholith and those mapped as of other ages are locally arbitrary and tentative.
Cambrian, undifferentiated (Phanerozoic | Paleozoic | Cambrian)
Cambrian, undifferentiated: comprises Deadwood formation, in south-central Montana, and Red Lion formation, Dry Creek shale, Hasmark formation, Pilgrim limestone, Silver Hill formation, Park shale, Meagher limestone, Wolsey shale, Flathead quartzite, and other units. In a few places quartzite of Cambrian age may be mapped with the Belt series or quartzite of Belt age with the Cambrian rocks.
Claggett formation (Phanerozoic | Mesozoic | Cretaceous-Late)
Claggett formation: chiefly dark-gray shale with iron-stained concretions; locally sandstone present; numerous bentonite beds near base.
Cretaceous, undifferentiated (Phanerozoic | Mesozoic | Cretaceous)
Cretaceous, undifferentiated: used in only a few areas, such as the Disturbed Belt east of Glacier National Park, where subdivision in difficult.
Devonian, undifferentiated (Phanerozoic | Paleozoic | Devonian)
Devonian, undifferentiated: comprises Three Forks formation consisting of carbonaceous and calcareous shale with some sandstone and limestone, Jefferson limestone, and unnamed units of Devonian age.
Eagle sandstone (Phanerozoic | Mesozoic | Cretaceous-Late)
Eagle sandstone: sandstone and shaly sandstone with lignite beds in basal part of upper unit (Keu). The Virgelle sandstone member (Kvi) at base is distinguished where possible. Near Yellowstone National Park rocks incorrectly called Laramide in early reports and now regarded as roughly equivalent to the Eagle sandstone are tentatively mapped as Eagle sandstone.
Empire shale (Proterozoic | Mesoproterozoic)
Empire shale: green dense, laminated shale with some red beds. Distinguished only in general vicinity of Helena.
Flaxville gravel (Phanerozoic | Cenozoic | Tertiary)
Flaxville gravel: Brown, yellow, and gray gravel, sand, and silt with marl and volcanic ash locally.
Fort Union formation (Phanerozoic | Cenozoic | Tertiary Cretaceous-Late | Paleocene)
Fort Union formation: Clay shale, siltstone, and sandstone; local lenses of impure limestone, and numerous lignitic beds; contains Tertiary plant and animal fossils but no dinosaurs; base generally placed at the lowest of the succession of lignite beds within it; includes the Tongue River member, Lebo shale member, and Tullock member.
Greenhorn formation (Phanerozoic | Mesozoic | Cretaceous-Late)
Greenhorn formation: mainly light-gray marl and calcareous shale.
Greyson shale (Proterozoic | Mesoproterozoic)
Greyson shale: dark-gray to dark-brown argillaceous and sandy rock; weathers brown or red; grades into the Spokane above and the Newland below. Distinguished only in the general vicinity of Helena.
Grinnell argillite (Proterozoic | Mesoproterozoic)
Grinnell argillite: reddish-purple and green argillite, quartzitic argillite, and some quartzite; generally contains some feldspar and carbonates.
Helena limestone (Proterozoic | Mesoproterozoic)
Helena limestone: gray, unevenly laminated limestone, argillaceous and dolomitic; weathers light brown or yellow. Segregation structures and stromatolites are common. Distinguished only in general vicinity of Helena.
Hell Creek formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous-Late Tertiary | Paleocene)
Hell Creek formation: somber-gray sandstone and greenish shaly clay and mudstone containing dinosaur bones; a few thin lignite and subbituminous coal beds.
Horsethief sandstone (Phanerozoic | Mesozoic | Cretaceous-Late)
Horsethief sandstone: shaly sandstone grading upward into massive brownish cliff-forming sandstone with local concentrations of magnetite in beds near top.
Judith River formation (Phanerozoic | Mesozoic | Cretaceous-Late)
Judith River formation: light-colored sandstone at top; lower third somber-gray siltstone and sandy shale; greenish-gray clay and some lignite beds; includes the Parkman sandstone member of south-central Montana.
Jurassic and Triassic rocks, undifferentiated (Phanerozoic | Mesozoic | Triassic Jurassic)
Jurassic and Triassic rocks, undifferentiated: in east-central Madison County where scale did not permit differentiation on map.
Jurassic, undifferentiated (Phanerozoic | Mesozoic | Jurassic)
Jurassic, undifferentiated: calcareous shale and sandstone; includes the Morrison formation, the Ellis group, Sundance formation, and other rocks of Jurassic age.
Kootenai formation and associated rocks (Phanerozoic | Mesozoic | Jurassic Cretaceous-Early)
Kootenai formation and associated rocks: conglomerate, sandstone, shale, and mudstone; purplish and green beds are common; mainly the Kootenai; in southern Montana includes strata that have been mapped as Cloverly formation. Includes Second Cat Creek and Third Cat Creek sands of drillers in central part of State; Sunburst sand of drillers in north-central part; and Cut Bank sand of drillers in western part. As here mapped, may locally include thin units of Jurassic age.
Lennep sandstone (Phanerozoic | Mesozoic | Cretaceous-Late)
Lennep sandstone: mainly dark-brown andesitic sandstone with intercalated shale; locally contains thin coal beds.
Livingston formation (Phanerozoic | Cenozoic | Tertiary Cretaceous)
Livingston formation: water-laid volcanic material, mainly andesitic in composition; includes agglomerate, conglomerate, sandstone, and shale. The name here is used only for the rocks orginally named, mainly near and north of Livingston. These rocks include age equivalents of various Cretaceous and Paleocene units.
Mississippian, undifferentiated (Phanerozoic | Paleozoic | Carboniferous Mississippian)
Mississippian, undifferentiated: sandstone, shale, and limestone, in part dolomitic, with chert nodules, some quartzite; includes Big Snowy group in central part of State, Madison group in central and southwestern parts; and Hannan and Brazer limestones in the northwestern part; may include small amounts of Pennsylvanian rocks in areas where stratigraphic studies are incomplete.
Missoula group (Proterozoic | Mesoproterozoic)
Missoula group: chiefly red, maroon, or purple argillite; sandy or quartzitic argillite, and generally impure quartzite and limestone. The larger limestone masses are similar to the Siyeh limestone of the Piegan group. The Missoula group includes numerous named formations, most of which cannot be traced with confidence far from their type localities. Among these are the Marsh shale in the Helena region, the Striped Peak and Libby formations in northwestern Montana, five near Missoula, and others in and south of Glacier National Park.
Missoula group (Proterozoic | Mesoproterozoic)
Missoula group: chiefly red, maroon, or purple argillite; sandy or quartzitic argillite, and generally impure quartzite and limestone. The larger limestone masses are similar to the Siyeh limestone of the Piegan group. The Missoula group includes numerous named formations, most of which cannot be traced with confidence far from their type localities. Among these are the Marsh shale in the Helena region, the Striped Peak and Libby formations in northwestern Montana, five near Missoula, and others in and south of Glacier National Park.
Newland limestone (Proterozoic | Mesoproterozoic)
Newland limestone: dark bluish-gray argillaceous, dolomitic limestone with some argillite, locally schistose; segregation structures not conspicuous. In central and western Montana the Newland and Wallace formations have been treated as essentially synonymous terms by some authors.
North Boulder group (Proterozoic | Mesoproterozoic)
North Boulder group: greenish-gray coarse conglomerate at base, with arkose, conglomerate, and sandy and silty strata above. Locally includes strata resembling the Greyson and Spokane shales, thought to rest directly on the pre-Belt complex of metamorphic rocks. Some areas shown as Spokane shale, and possibly other units may include rocks of the North Boulder group. Distinguished from the vicinity of North Boulder River eastward along and north of Jefferson River and in the Bridger Range.
Ordovician, undifferentiated (Phanerozoic | Paleozoic | Ordovician)
Ordovician, undifferentiated: Mainly Bighorn dolomite; near Idaho, Kinnikinic quartzite.
Paleozoic rocks, undifferentiated (Phanerozoic | Paleozoic)
Paleozoic rocks, undifferentiated: in east-central Madison County where scale did not permit differentiation on map.
Pennsylvanian, undifferentiated (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Pennsylvanian, undifferentiated: in western Montana is mainly the Quadrant quartzite but includes limestone and other rocks of Pennsylvanian age so far as present data permit. Farther east other formations of Pennsylvanian or possible Pennsylvanian age are included.
Permian, undifferentiated (Phanerozoic | Paleozoic | Permian)
Permian, undifferentiated: chert, sandstone, limestone, quartzite, and shale with rock phosphate mostly at base; mainly Phosphoria formation
Permian, undifferentiated (Phanerozoic | Paleozoic | Permian)
Permian, undifferentiated: chert, sandstone, limestone, quartzite, and shale with rock phosphate mostly at base; mainly Phosphoria formation
Piegan group (Proterozoic | Mesoproterozoic)
Piegan group: most of the Piegan group is subdivided into formations that are in part equivalent to each other. Where correlations are relatively doubtful the group designation is retained. Carbonate-bearing rocks predominate in the group, but the proportions and character of the impurities in these rocks and the relations to non-carbonate-bearing rocks vary from place to place.
Piegan group (Proterozoic | Mesoproterozoic)
Piegan group: most of the Piegan group is subdivided into formations that are in part equivalent to each other. Where correlations are relatively doubtful the group designation is retained. Carbonate-bearing rocks predominate in the group, but the proportions and character of the impurities in these rocks and the relations to non-carbonate-bearing rocks vary from place to place.
Pierre shale (Phanerozoic | Mesozoic | Cretaceous-Late)
Pierre shale: dark-gray clay shale with calcareous and ferruginous concretions and sandy members.
Prichard formation (Proterozoic | Mesoproterozoic)
Prichard formation: dark-gray, generally argillaceous rocks, locally sandy or quartzitic; locally metamorphosed to schist.
Siyeh limestone (Proterozoic | Mesoproterozoic)
Siyeh limestone: crystalline limestone of varying impurity; mostly thick bedded or massive, but with thin wavy banding on fresh fractures within the beds; dusky blue or greenish where fresh, weathering orange and brownish; "molar tooth", similar structures, and stromatolites are common.
Spokane shale (Proterozoic | Mesoproterozoic)
Spokane shale: red or red-purple shale with numerous green beds locally and some quartzite; grades into the Empire above and the Greyson below and in some areas as mapped probably includes all or part of Empire and Greyson shales. The name has been used over a wide area in Montana, but in a strict sense can be used safely only in the general vicinity of Helena.
Stillwater complex (Archean Proterozoic(?) preCambrian-Proterozoic(?) preCambrian(?) Phanerozoic | Paleozoic(?) Mesozoic(?) Cenozoic | Cambrian(?) Ordovician(?) Silurian(?) Devonian(?) Carboniferous(?) Permian(?) Triassic(?) Jurassic(?) Cretaceous(?) Tertiary)
Stillwater complex: consists chiefly of ultrabasic intrusive rocks and metamorphic rocks not yet named or subdivided.
St. Mary River formation (Phanerozoic | Mesozoic | Cretaceous-Late)
St. Mary River formation: Greenish-gray clay with local nodular limestone and crossbedded sandstone.
Tertiary dikes and sills (Phanerozoic | Cenozoic | Tertiary)
Tertiary dikes and sills: mostly granophyric rocks in west and alkalic rocks in east, but includes some quartz diorite and other rocks. These dikes and sills are in part offshoots of the Tertiary coarse-grained intrusive rocks.
Tertiary sedimentary rocks, undifferentiated (Phanerozoic | Cenozoic | Tertiary)
Tertiary sedimentary rocks, undifferentiated: clastic deposits in western Montana, mostly in valleys, and in most places not divided into formations; mostly poorly consolidated gravel, sand, silt, and clay; includes some tuffaceous material and locally lenses of lignite and bentonite; a little hot spring tufa; and in areas not yet mapped in detail, lava may be included. These rocks were in part laid down in lakes but a large part was formed in streams and alluvial fans. These rocks are Tertiary in age and as now mapped may even include some beds of Cretaceous age. Some late Tertiary terrace deposits may be included.
Tertiary volcanic rocks (Phanerozoic | Cenozoic | Tertiary)
Tertiary volcanic rocks: Flows and associated pyroclastic deposits, with subordinate amounts of intercalated sedimentary beds and lignite. The volcanic material is mostly latite, quartz latite, and andesite but includes some rhyolite and basalt. The distinction between Tertiary and pre-Tertiary volcanic rocks was not made in some of the reports used in the complilation. Hence in the less well-known areas some pre-Tertiary volcanic rocks may be included.
Thermopolis shale (Phanerozoic | Mesozoic | Cretaceous-Early)
Thermopolis shale: dark-gray shale with some sandstone. The subsurface consists of Muddy sandstone member or Newcastle sandstone member at top, Skull Creek shale member in middle, and Fall River sandstone or First Cat Creek sand of drillers at base.
Triassic, undifferentiated (Phanerozoic | Mesozoic | Triassic)
Triassic, undifferentiated: conglomerate, sandstone, shale, and impure limestone belonging to the Dinwoody and Thaynes formations and other units of Triassic age, and the Chugwater of Triassic and Permian age.
Two Medicine formation (Phanerozoic | Mesozoic | Cretaceous-Late)
Two Medicine formation: greenish-gray clay with local nodular limestone and crossbedded sandstone; locally some coal in lower part. Rocks equivalent to Judith River formation, Claggett formation, and upper part of Eagle sandstone are included in this unit.
Wallace formation (Proterozoic | Mesoproterozoic)
Wallace formation: A heterogeneous unit that includes dark-gray argillite, arenaceous and argillaceous limestone, in part dolomitic, and gray limy quartzite, with shale and sandstone in large areas. The argillaceous and sandy or quartzitic rocks are commonly slightly calcareous. The dominantly carbonate-rich rocks contain "molar tooth" or segregation structures. Commonly characterized by thin laminae. Locally red rocks near the top may represent a transition into the Missoula group.
Wasatch formation (Phanerozoic | Cenozoic | Tertiary)
Wasatch formation: Light-colored massive sandstone; drab-colored shale and coal in southeastern Montana; and variegated, dominantly red beds of clay and sandstone in north-central Montana.
White River formation (Phanerozoic | Cenozoic | Tertiary)
White River formation: Light-colored clay with minor beds of sandstone and local beds of nodular limestone.
Willow Creek formation (Phanerozoic | Cenozoic | Cretaceous-Late)
Willow Creek formation: Variegated clay and soft sandstone, chiefly maroon to chocolate brown; local lenses of purple-gray nodular limestone.
North Carolina
Alligator Back Formation; Gneiss (Late Proterozoic)
Gneiss - finely laminated to thin layered; locally contains massive gneiss and micaceous granule conglomerate; includes schist, phyllite, and amphibolite.
Alligator Back Formation; Mica schist and phyllite (Late Proterozoic)
Mica schist and phyllite - laminated to thin layered; interlayered with minor biotite-muscovite gneiss and amphibolite.
Amphibolite (Cambrian/Late Proterozoic)
Amphibolite - metamorphosed mafic extrusive and intrusive rock; includes hornblende gneiss, thin layers of mica schist, and small nonlayered masses of metadiorite and metagabbro.
Amphibolite (Cambrian/Late Proterozoic)
Amphibolite - equigranular, massive to well foliated, dioritic to basaltic dikes and sills; variably metamorphosed.
Amphibolite (Cambrian/Late Proterozoic)
Amphibolite - equigranular, massive to well foliated, dioritic to basaltic dikes and sills; variably metamorphosed.
Amphibolite (Cambrian/Late Proterozoic)
Amphibolite - metamorphosed mafic extrusive and intrusive rock; includes hornblende gneiss, thin layers of mica schist, calc-silicate rock, and, rarely, marble. Also includes small masses of metadiorite and metagabbro.
Amphibolite and Biotite Gneiss (Cambrian/Late Proterozoic)
Amphibolite and Biotite Gneiss - interlayered; minor layers and lenses of hornblende gneiss, metagabbro, mica schist, and granitic rock.
Ashe Metamorphic Suite and Tallulah Falls Formation; Biotite gneiss (Late Proterozoic)
Biotite gneiss - interlayered with biotite-garnet gneiss, biotite-muscovite schist, garnet-mica schist, and amphibolite.
Ashe Metamorphic Suite and Tallulah Falls Formation; Metagraywacke (Late Proterozoic)
Metagraywacke - foliated to massive, locally conglomeratic; interlayered and gradational with mica schist, muscovite-biotite gneiss, and rare graphitic schist.
Ashe Metamorphic Suite and Tallulah Falls Formation; Mica schist (Late Proterozoic)
Mica schist - locally sulfidic and graphitic; minor interlayered mica gneiss and amphibolite.
Ashe Metamorphic Suite and Tallulah Falls Formation; Muscovite-biotite gneiss (Late Proterozoic)
Muscovite-biotite gneiss - locally sulfidic; interlayered and gradational with mica schist, minor amphibolite, and hornblende gneiss.
Banded Gneiss (Cambrian/Late Proterozoic)
Banded Gneiss - interlayered with calc-silicate rock, metaconglomerate, amphibolite, sillimanite-mica schist, and granitic rock.
Battleground Formation (Late Proterozoic)
Battleground Formation - quartz-sericite schist with metavolcanic rock, quartz-pebble metaconglomerate, kyanite-sillimanite quartzite, and garnet-quartz rock.
Beaufort Formation, Undivided (Tertiary)
Beaufort Formation, Undivided - Unnamed upper member: sand and silty clay, glauconitic, fossiliferous, and locally calcareous. Jericho Run Member: siliceous mudstone with sandstone lenses, thin bedded; basal phosphatic pebble conglomerate.
Belgrade Formation, Undivided (Tertiary)
Belgrade Formation, Undivided - Pollocksville Member: oyster-shell mounds in tan to orange sand matrix, indurated locally. Haywood Landing Member: fossiliferous clayey sand, gray to brown. Members grade into each other laterally.
Biotite Gneiss and Schist (Cambrian/Late Proterozoic)
Biotite Gneiss and Schist - inequigranular and megacrystic; abundant potassic feldspar and garnet; interlayered and gradational with calc-silicate rock, sillimanite-mica schist, mica schist, and amphibolite. Contains small masses of granitic rock.
Biotite Gneiss and Schist (Cambrian/Late Proterozoic)
Biotite Gneiss and Schist - (Located in the Lilesville granite aureole) inequigranular, locally abundant potassic feldspar and garnet; interlayered and gradational with calc-silicate rock, sillimanite-mica schist, mica schist, and amphibolite. Contains small masses of granitic rock.
Biotite Gneiss and Schist (Cambrian/Late Proterozoic)
Biotite Gneiss and Schist - inequigranular and megacrystic; in places contains garnet; interlayered and gradational with mica schist and amphibolite; includes small masses of granitic rock.
Biotite Gneiss and Schist (Cambrian/Late Proterozoic)
Biotite Gneiss and Schist - inequigranular, locally abundant potassic feldspar and garnet; interlayered and gradational with calc-silicate rock, sillimanite-mica schist, mica schist, and amphibolite. Contains small masses of granitic rock.
Biotite Granitic Gneiss (Middle Proterozoic)
Biotite Granitic Gneiss - unconformity; pinkish gray to light gray, massive to well-foliated, granitic to quartz monzonitic; includes variably mylonitized orthogneiss and paragneiss, interlayered amphibolite, calc-silicate rock, and marble. Includes granites of the Bryson City area, Straight Fork window, and Elk Park Plutonic Suite.
Biotite Granitic Gneiss (Middle Proterozoic)
Biotite Granitic Gneiss (950-1250 my) - unconformity; contains paragneiss and granitic to quartz monzonitic orthogneiss; locally schistose and mylonitic. Locally includes tectonic slices, infolded remnants, or recrystallized equivalents of the Grandfather Mountain Formation. Equivalent to the Wilson Creek Gneiss.
Blacksburg Formation (Cambrian/Late Proterozoic)
Blacksburg Formation - sericite schist, locally with graphite, phyllite with sericite quartzite, banded marble, amphibolite, and minor calc-silicate rock.
Blowing Rock Gneiss (Middle Proterozoic)
Blowing Rock Gneiss (1000 my) - unconformity; abundant white potassic feldspar megacrysts in finely banded biotite schist, locally calcareous; interlayered with quartz-feldspar schist, calcareous biotite schist, phyllite, black slate, calcareous quartzite, sulfidic greenstone, and siliceous tuff.
Cape Fear Formation (Cretaceous)
Cape Fear Formation - sandstone and sandy mudstone, yellowish gray to bluish gray, mottled red to yellowish orange, indurated, graded and laterally continuos bedding, blocky clay, faint cross-bedding, feldspar and mica common.
Castle Hayne Formation; Comfort Member and New Hanover Member, undivided (Tertiary)
Comfort Member and New Hanover Member, undivided - Comfort Member: bryozoan-echinoid skeletal limestone, locally dolomitized, solution cavities common. New Hanover Member: phosphate-pebble conglomerate, micritic, thin; restricted to basal part of Castle Hayne Formation in southeastern counties.
Chilhowee Group, Grandfather Mountain Formation; Greenstone (Late Proterozoic)
Greenstone - schistose to massive, amygdaloidal; interlayered with metasedimentary rocks. Includes Montezuma Member (metabasalt) in upper part.
Chilhowee Group, Grandfather Mountain Formation; Metasiltstone (Late Proterozoic)
Metasiltstone - locally contains thin bedded iron-bearing dolomitic marble; interlayered with phyllite, metagraywacke, and meta-arkose.
Chilhowee Group; Lower Chilhowee (Cambrian)
Lower Chilhowee - feldspathic quartzite, white to yellowish gray. Minor silty slate, feldspathic metasiltstone, and metaconglomerate in lower part.
Chilhowee Group; Lower Chilhowee (Cambrian)
Lower Chilhowee - feldspathic arenite, white to yellowish gray. Minor silty shale, feldspathic siltstone, and conglomerate in lower part. Includes Unicoi Formation of Hot Springs window.
Chilhowee Group; Upper Chilhowee (Cambrian)
Upper Chilhowee - vitreous quartz arenite, white to light gray; interbedded sandy siltstone and shale. Erwin and Hampton formations of Hot Springs window.
Chilhowee Group; Upper Chilhowee (Cambrian)
Upper Chilhowee - vitreous quartzite, white to light gray; interbedded sandy metasiltstone and slate.
Cid Formation; Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)
(southwest of Asheboro); Felsic Metavolcanic Rock - metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate metavolcanic rock, meta-argillite, and metamudstone.
Cid Formation; Mafic Metavolcanic Rock (Cambrian/Late Proterozoic)
(Southwest of Asheboro); Mafic Metavolcanic Rock - metamorphosed basaltic flows and tuffs, dark green to black; interbedded with felsic and intermediate metavolcanic rock and metamudstone.
Cid Formation; Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)
(Southwest of Asheboro); Metamudstone and Meta-Argillite - thin to thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone, metaconglomerate, and metavolcanic rock.
Coweeta Group (Late Proterozoic)
Coweeta Group - quartz dioritic gneiss, feldspar-quartz-biotite gneiss, metasandstone and quartzite, alumino-silicate schist, garnetiferous biotite gneiss, and minor amphibolite. Quartz dioritic gneiss predominant.
Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)
Felsic Metavolcanic Rock - metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate metavolcanic rock, meta-argillite, and metamudstone.
Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)
Felsic Metavolcanic Rock - metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; minor mafic and intermediate metavolcanic rock.
Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)
Felsic Metavolcanic Rock - metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate metavolcanic rock, meta-argillite, and metamudstone.
Felsic Mica Gneiss (Cambrian/Late Proterozoic)
Felsic Mica Gneiss - interlayered with biotite and hornblende gneiss and schist.
Felsic Mica Gneiss (Cambrian/Late Proterozoic)
Felsic Mica Gneiss - interlayered with graphitic mica schist and mica-garnet schist, commonly with kyanite; minor hornblende gneiss.
Fine-grained Biotite Gneiss (Cambrian/Late Proterozoic)
Fine-grained Biotite Gneiss - strongly foliated; minor layers of amphibolite and muscovite schist.
Fine-grained Biotite Gneiss (Cambrian/Late Proterozoic)
Fine-grained Biotite Gneiss - strongly foliated; minor layers of amphibolite and muscovite schist.
Fine-grained Biotite Gneiss (Cambrian/Late Proterozoic)
Fine-grained Biotite Gneiss - massive to strongly foliated; minor layers of amphibolite and muscovite schist.
Floyd Church Formation; Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)
(Southwest of Asheboro); Metamudstone and Meta-Argillite - thin to thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone, metaconglomerate, and metavolcanic rock.
Injected Gneiss (Cambrian/Late Proterozoic)
Injected Gneiss - biotite gneiss and schist intruded by numerous sills and dikes of granite, pegmatite, and aplite; minor hornblende gneiss.
Intermediate Metavolcanic Rock (Cambrian/Late Proterozoic)
Intermediate Metavolcanic Rock - metamorphosed andesitic tuffs and flows, medium to dark grayish green; minor felsic and mafic metavolcanic rock.
Intermediate Metavolcanic Rock (Cambrian/Late Proterozoic)
Intermediate Metavolcanic Rock - metamorphosed andesitic tuffs and flows, medium to dark grayish green; minor felsic and mafic metavolcanic rock.
Lineated Felsic Mica Gneiss (Cambrian/Late Proterozoic)
Lineated Felsic Mica Gneiss - white to pink, with strong lineation of muscovite-biotite streaks and prismatic quartz aggregates; planar foliation and layering weak; minor mica schist and hornblende gneiss.
Linville Metadiabase (Late Proterozoic)
Linville Metadiabase - metadiabase, greenstone, and amphibolite dikes and sills; massive to schistose.
Mafic Metavolcanic Rock (Cambrian/Late Proterozoic)
Mafic Metavolcanic Rock - metamorphosed basaltic flows and tuffs, dark green to black; interbedded with felsic and intermediate metavolcanic rock and metamudstone.
Mafic Metavolcanic Rock (Cambrian/Late Proterozoic)
Mafic Metavolcanic Rock - metamorphosed basaltic flows and tuffs, dark green to black; interbedded with felsic and intermediate metavolcanic rock and metamudstone.
Megacrystic Biotite Gneiss (Cambrian/Late Proterozoic)
Megacrystic Biotite Gneiss - poorly layered to massive; megacrysts of microcline and quartz; local mica schist, amphibolite, and biotite gneiss
Metagraywacke, Amphibolite, and Kyanite Schist (Cambrian/Late Proterozoic)
Metagraywacke, Amphibolite, and Kyanite Schist - metagraywacke (biotite gneiss) interlayered and gradational with amphibolite and kyanite schist; minor ultramafic and granitic rock.
Metagraywacke and Muscovite-Biotite Schist (Cambrian/Late Proterozoic)
Metagraywacke and Muscovite-Biotite Schist - metagraywacke (biotite gneiss) interlayered and gradational with muscovite-biotite schist; minor marble and granitic rock.
Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)
Metamudstone and Meta-Argillite - bedding plane and axial-planar cleavage common; interbedded with metasandstone, meta-conglomerate, and metavolcanic rock.
Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)
Metamudstone and Meta-Argillite - thin to thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone, metaconglomerate, and metavolcanic rock.
Metavolcanic-Epiclastic Rock (Cambrian/Late Proterozoic)
Metavolcanic-Epiclastic Rock - metamorphosed argillite, mudstone, volcanic sandstone, and conglomerate, and volcanic rock.
Metavolcanic-Epiclastic Rock (Cambrian/Late Proterozoic)
Metavolcanic-Epiclastic Rock - metamorphosed argillite, mudstone, volcanic sandstone, conglomerate, and volcanic rock.
Metavolcanic Rock (Cambrian/Late Proterozoic)
Metavolcanic Rock - interbedded felsic to mafic tuffs and flowrock.
Mica Schist (Cambrian/Late Proterozoic)
Mica Schist - contains garnet, staurolite, kyanite, or sillimanite; includes lenses and layers of quartz schist, micaceous quartzite, biotite gneiss, amphibolite, and phyllite.
Mica Schist (Cambrian/Late Proterozoic)
Mica Schist - Garnet, staurolite, kyanite, or sillimanite occur locally; lenses and layers of quartz schist, micaceous quartzite, calc-silicate rock, biotite gneiss, amphibolite, and phyllite.
Middendorf Formation (Cretaceous)
Middendorf Formation - sand, sandstone, and mudstone, gray to pale gray with an orange cast, mottled; clay balls and iron-cemented concretions common, beds laterally discontinuous, cross-bedding common.
Migmatitic Biotite-Hornblende Gneisses (Middle Proterozoic)
Migmatitic Biotite-Hornblende Gneisses (1214 my) - unconformity; layered biotite-granite gneiss, biotite-hornblende gneiss, amphibolite, calc-silicate rock; locally contains relict granulite facies rock.
Migmatitic Granitic Gneiss (Ordovician/Cambrian)
Migmatitic Granitic Gneiss - foliated to massive, granitic to quartz dioritic; biotite gneiss and amphibolite common.
Mineral Bluff Formation (Late Proterozoic)
Mineral Bluff Formation - quartz-chlorite-sericite schist and phyllite with thin quartzite layers and minor interbedded graphitic schist, garnet-mica schist, staurolite schist, cross-biotite schist, and dark slate.
Mount Rogers Formation; Metagraywacke (Late Proterozoic)
Metagraywacke - interlayered with metaconglomerate, laminated metasiltstone, and slate; minor calcareous metasandstone, greenstone, and metarhyolite.
Murphy Marble, Andrews Formation, and Nottely Quartzite, undivided (Late Proterozoic)
Murphy Marble, Andrews Formation, and Nottely Quartzite, undivided - Murphy Marble: calcareous to dolomitic; Andrews Formation: calcareous cross-biotite schist; Nottely Quartzite: meta-orthoquartzite with slate.
Nantahala Formation and Tusquitee Quartzite, undivided (Late Proterozoic)
Nantahala Formation and Tusquitee Quartzite, undivided - Nantahala Formation: slate and metasiltstone, dark gray, laminated to thin bedded, sulfidic; Tusquitee Quartzite: white to light yellowish gray, numerous, thin slate layers.
Newark Supergroup, Chatham Group; Chatham Group, Undivided (Triassic)
Chatham Group, Undivided - conglomerate, fanglomerate, sandstone, and mudstone. Conglomerate and fanglomerate shown by pattern.
Newark Supergroup, Chatham Group; Cumnock Formation (Triassic)
Cumnock Formation - sandstone and mudstone, gray to black; coal beds and carbonaceous shale. Grades into Pekin and Sanford formations.
Newark Supergroup, Chatham Group; Pekin Formation (Triassic)
Pekin Formation - conglomerate, sandstone, and mudstone.
Newark Supergroup, Chatham Group; Sanford Formation (Triassic)
Sanford Formation - conglomerate, fanglomerate, sandstone, and mudstone.
Newark Supergroup, Dan River Group; Dan River Group, Undivided (Triassic)
Dan River Group, Undivided - basin-margin conglomerate and sandstone, red to brown, interfingering with basin-center sandstone and mudstone, green to brown. Conglomerate shown by pattern.
Newark Supergroup, Dan River Group; Pine Hall Formation (Triassic)
Pine Hall Formation - sandstone, mudstone, and conglomerate, yellowish orange to brown.
Newark Supergroup, Dan River Group; Stoneville Formation (Triassic)
Stoneville Formation - conglomerate, sandstone, and mudstone, lenticular and laterally-gradational bedding.
Ocoee Supergroup, Great Smokey Group; Anakeesta Formation (Late Proterozoic)
Anakeesta Formation - slate to schist, dark gray, graphitic and sulfidic; includes interbedded argillaceous, feldspathic metagraywacke.
Ocoee Supergroup, Great Smokey Group; Copperhill Formation (Late Proterozoic)
Copperhill Formation - metagraywacke, massive, graded bedding common; includes dark-gray slate, mica schist, and nodular calc-silicate rock.
Ocoee Supergroup, Great Smokey Group; Metasandstone, Metagraywacke, Metasiltstone, and Mica Schist (Late Proterozoic)
Metasandstone, Metagraywacke, Metasiltstone, and Mica Schist - beds and lenses of calc-silicate rock locally abundant; garnet, staurolite, and cross-biotite porphyroblasts common in fine-grained layers. Includes Hughes Gap and Hothouse formations in southern area; Horse Branch Member of Ammons Formation and Grassy Branch Formation in northern area.
Ocoee Supergroup, Great Smokey Group; Slate of Copperhill Formation (Late Proterozoic)
Slate of Copperhill Formation - slate to phyllite, dark gray, graphitic, sulfidic; includes metagraywacke with local graded bedding.
Ocoee Supergroup; Great Smokey Group, undivided (Late Proterozoic)
Great Smokey Group, undivided - thick metasedimentary sequence of massive to graded beds of metagraywacke and metasiltstone with interbedded graphitic and sulfidic slate and schist.
Ocoee Supergroup, Great Smokey Group; Wehutty Formation (Late Proterozoic)
Wehutty Formation - slate to schist, dark gray, graphitic and sulfidic; includes mica schist, metagraywacke, and metaconglomerate.
Ocoee Supergroup, Snowbird Group; Longarm Quartzite (Late Proterozoic)
Longarm Quartzite - cross-bedded, feldspathic, locally conglomeratic; includes dark slate and metasiltstone.
Ocoee Supergroup, Snowbird Group; Pigeon Siltstone (Late Proterozoic)
Pigeon Siltstone - thin bedded to laminated, commonly cross-bedded, metamorphosed; locally includes argillite and calcareous and arkeritic metasiltstone grading to silty metalimestone.
Ocoee Supergroup, Snowbird Group; Roaring Fork Sandstone (Late Proterozoic)
Roaring Fork Sandstone - greenish gray, fine to medium grained, locally cross-bedded, metamorphosed; interbedded metasiltstone and phyllite.
Ocoee Supergroup, Snowbird Group, undivided (Late Proterozoic)
Snowbird Group, undivided - feldspathic metasiltstone, metasandstone, and phyllite. Basal schist contains lenses of quartz-pebble conglomerate.
Ocoee Supergroup, Snowbird Group; Wading Branch Formation (Late Proterozoic)
Wading Branch Formation - sandy slate to coarse-grained pebbly metagraywacke with local graded bedding. Basal quartz-sericite schist or phyllite.
Ocoee Supergroup, Walden Creek Group; Sandsuck Formation (Late Proterozoic)
Sandsuck Formation - slate and metasiltstone, dark green to black. Metaconglomerate lentils in upper part; calcareous metasandstone, sandy metalimestone, and quartzite in lower part.
Peedee Formation (Cretaceous)
Peedee Formation - sand, clayey sand, and clay, greenish gray to olive black, massive, glauconitic, locally fossiliferous and calcareous. Patches of sandy molluscan-mold limestone in upper part.
Phyllite and Schist (Cambrian/Late Proterozoic)
Phyllite and Schist - minor biotite, pyrite, and sillimanite; includes minor quartzite.
Phyllite and Schist (Cambrian/Late Proterozoic)
Phyllite and Schist - minor biotite and pyrite; includes phyllonite, sheared fine-grained metasediment and metavolcanic rock.
Phyllite and Schist (Cambrian/Late Proterozoic)
Phyllite and Schist - includes phyllonite and interlayered biotite gneiss.
Phyllite and Schist (Cambrian/Late Proterozoic)
Phyllite and Schist - locally laminated and pyritic; includes phyllonite, sheared fine-grained metasediment, and metavolcanic rock. In Lilesville granite aureole, includes hornfels.
Phyllite and Schist (Cambrian/Late Proterozoic)
Phyllite and Schist - minor biotite and pyrite; includes phyllonite, sheared fine-grained metasediment and metavolcanic rock.
River Bend Formation (Tertiary)
River Bend Formation - limestone, calcarenite overlain by and intercalated with indurated, sandy, molluscan-mold limestone.
Rocks of Brevard Fault Zone (Uncertain, possibly Permian or Devonian)
Rocks of Brevard Fault Zone - "fish scale" schist and phyllonite, graphitic; interlayered with feldspathic metasandstone, marble lenses.
Rome Formation (Cambrian)
Rome Formation - shale and siltstone, variegated red to brown; interbedded fine-grained sandstone and shaly dolomite.
Surficial Deposits, Undivided (Quaternary)
Surficial Deposits, Undivided - sand, clay, gravel, and peat deposited in marine, fluvial, eolian, and lacustrine environments. Quaternary deposits not shown at altitudes greater than approx. 205 feet above mean sea level (Suffolk Scarp, in part).
Terrace Deposits and Upland Sediment (Tertiary)
Terrace Deposits and Upland Sediment - gravel, clayey sand, and sand, minor iron-oxide cemented sandstone.
Tillery Formation; Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)
(Southwest of Asheboro); Metamudstone and Meta-Argillite - thin to thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone, metaconglomerate, and metavolcanic rock.
Uwharrie Formation; Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)
(at Asheboro and to south); Felsic Metavolcanic Rock - metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate metavolcanic rock, meta-argillite, and metamudstone.
Volcanic Metaconglomerate (Cambrian/Late Proterozoic)
Volcanic Metaconglomerate - includes metagraywacke and metamudstone.
Waccamaw Formation (Tertiary)
Waccamaw Formation - fossiliferous sand with silt and clay, bluish-gray to tan, loosely consolidated. Straddles Pleistocene-Pliocene boundary.
Yadkin Formation (Cambrian/Late Proterozoic)
Yadkin Formation - metamorphosed graywacke, volcanic sandstone, and siltstone; interbedded with mafic and intermediate metavolcanic flows and tuffs.
Yorktown Formation and Duplin Formation, Undivided (Tertiary)
Yorktown Formation and Duplin Formation, Undivided - Yorktown Formation: fossiliferous clay with varying amounts of fine-grained sand, bluish gray, shell material commonly concentrated in lenses; mainly in area north of Neuse River. Duplin Formation: shelly, medium- to coarse-grained sand, sandy marl, and limestone, bluish gray; mainly in area south of Neuse River.
North Dakota
Bullion Creek Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene)
Yellow-brown silt, sand, clay, sandstone, and lignite; river, lake, and swamp sediment; as thick as 200 meters (600 feet).
Cannonball Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene)
Olive-brown sand, shale, and sandstone; marine shoreline and offshore sediment; as thick as 120 meters (400 feet).
Fox Hills Formation (Phanerozoic | Mesozoic | Cretaceous-Late)
Olive-brown sand, shale, and sandstone; marine shoreline and offshore sediment; as thick as 120 meters (400 feet).
Glacial Sediment- Collapsed/Draped Transition Sediments (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- Collapsed Glacial Sediment (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- Collapsed Glacial Sediment (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- Collapsed Glacial Sediment (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- Collapsed Glacial Sediment (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- Glacial Sediment Draped Over Pre-existing Topography (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment-Glacial Sediment Draped Over Pre-existing Topography (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- Glacial Sediment on Subglacially Molded Surfaces (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- Glacial Sediment on Thrust Masses (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- River-Eroded Glacial Sediment (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- Slopwash-Eroded Glacial Sediment (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Glacial Sediment- Wave-Eroded Glacial Sediment (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene)
Unbedded, unsorted mixture of clay, silt, sand, and pebbles, and a few cobbles and boulders; as thick as 30 meters (100 feet)
Golden Valley Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene)
Upper member: Yellow-brown micaceous sandstone, sand, silt, and clay; fluvial sediment; as thick as 60 meters (200 feet). Lower member: White or yellow clay, silt, and sand; a weatering zone developed on underlying unit; as thick as 20 meters (65 feet).
Hell Creek Formation (Phanerozoic | Mesozoic | Cretaceous-Late)
Gray sand, silt, clay, and sandstone; river sediment; as thick as 150 meters (500 feet).
Ludlow Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene)
Gray-brown and yellow-brown silt, sand, clay and sandstone, and lignite; river, lake, and swamp sediment; as thick as 100 meters (300 feet).
Oahe Formation- River Sediment (Phanerozoic | Cenozoic | Quaternary | Holocene)
Dark, obscurely bedded clay and silt (overbank sediment); generally overlying cross-bedded sand (channel sediment); as thick as ten meters (30 feet); on flood plains of modern streams.
Sentinel Butte Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene)
Gray-brown silt, sand, clay, sandstone, and lignite; river, lake, and swamp sediment; as thick as 200 meters (600 feet).
Slope Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene)
Gray-brown and yellow-brown silt, sand, clay, sandstone, and lignite; river, lake, and swamp sediment; as thick as 100 meters (300 feet).
White River Group (Phanerozoic | Cenozoic | Tertiary | Oligocene)
Brule Formation: Pinkish siltstone, clay, and sand; river and lake sediment; as thick as 50 meters (150 feet). Chadron Formation: Light-colored sand with quartzite and porphyry pebbles, overlain by dark clay; river and lake sediment; as thick as 30 meters (100 feet).
Nebraska
Admire Group (Phanerozoic | Paleozoic | Permian)
Shale and interbedded limestone. Shale is dark gray to light gray, brown, red, or green, sandy, calcareous, and fossiliferous. Interbedded dark- to light-gray, very thin to medium bedded, argillaceous, very fossiliferous limestone beds. Near top of unit a fine-grained, micaceous sandstone bed underlies a stromatolite limestone bed which has distinctive lobate bedding. Approx. max thickness 150 ft
Arikaree Group (Phanerozoic | Cenozoic | Tertiary | Oligocene Miocene)
Consists mainly of gray, fine, loose to compact sand that has layers of hard, fine-grained dark-gray concretions which vary from few in to 15 in and often have tabular form. Includes a large amount of volcanic ash mixed in with the sand. Contains a number of channels filled with coarse conglomerate along ridge south of North Platte River. About 500 ft thick.
Carlile Shale (Phanerozoic | Mesozoic | Cretaceous-Late)
Shale, limestone, and sandstone. At top, locally 5 feet of gray to pale-yellowish brown siltstone or very fine grained sandstone. Upper 200 feet of shale is drak gray to medium gray; locally contains ironstone concretions, and interbedded with thin siltstone. Lower 80 feet of shale is medium gray, calcareous, and contains many very thin bedded, fossiliferous, shaly limestone and calcareous shale layers. Approx. max thickness 300 ft.
Dakota Group (Phanerozoic | Mesozoic | Cretaceous-Early)
Upper part is white, light-gray, brownish-gray, yellow, redish-brown, and red sandstone and shale. Sandstone is very fine to coarse grained, friable, micaeous, crossbedded, and lenticular; locally contains gravel near base. contains numerous zones of ironstone and siltstone concretions of variable thickness. Middle part is light-gray, yellow, red brown and dark-gray, sandy carbonaceous shale; commonly contains a zone of concretions near top. Lower part is sandstone similar to that in upper except there are zones of siderite concretions and, locally a basal zone of chert pebbles. Approx. max thickness 600 ft.
Fox Hills Formation (Phanerozoic | Mesozoic | Cretaceous-Late)
Consists of fossiliferous, gray, ferruginous and yellowish fine-grained sandstone, arenaceous clays and a few interbeds of gray to brown sandy shale and coal totaling 172 ft thick at that section. Estimated thickness 500 ft.
Greenhorn Limestone and Graneros Shale (Phanerozoic | Mesozoic | Cretaceous-Late)
Greenhorn Limestone- medium- to light-gray limestone interbedded with argillaceous limestone, marl and calcareous shale; contains Inoceramus fossils. Upper and lower contacts gradational. Approx. max thickness 30 ft. Graneros Shale- medium- to dark-gray, partly calcareous shale. Interbeds of siltstone, sandstone, and carbonaceous shale, and thin bentonite layers in upper part. Approx. max thickness 60 ft.
Ogallala Group or Formation (Phanerozoic | Cenozoic | Tertiary | Miocene)
Silt, sand, sandstone, gravel and conglomerate. Predominantly interfingered fine- to coarse grained, poorly sorted, arkosic, fluvial deposits of light-gray, light-olive-gray, and grayish-green calcareous silt and sand, and locally poorly consolidated conglomerate, sandstone, and siltstone.
Shawnee Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Virgilian])
Limestone, shale and siltstone. Limestone is dark gray to very light gray, yellowish gray, very thin bedded to massive bedded, and fossiliferous; locally the thin bedds are argillaceous other beds are oolitic and a few contain chert. Shale is medium gray, greenish gray, pale red, dark redish brown, black, sandy fossiliferous and calcareous; black shale in part is fissile. Siltstone is light gray to greenish yellow, massive, calcareous; locally sandy. Approx. max thickness 200 ft
Wabaunsee Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Virgilian])
Shale, sandstone, and interbedded limestone. Shale is light gray to dark gray, greenish gray, red, or black; contains very thin layers of siltstone; locally very fossiliferous, carbonaceous. Sandstone is brownish gray to yellowish gray, or gray, argillaceous , and micaceous. Limestone is dark gray to medium gray, yellowish gray, thin bedded to thick bedded; very fossiliferous. Contains coal beds less than 1 ft. thick. Approx. max thickness 300 ft
White River Group (Phanerozoic | Cenozoic | Tertiary | Oligocene)
Clay, some claystone, silt and siltstone. Predominantly greenish gray and volcaniclastic. Other occurrences are greenish gray to white and bentonitic. Local channel sandstone at base. Aprox thickness 195 ft.
New Hampshire
Ayer Granodiorite (Early Silurian)
Ayer Granodiorite - Gneissic granite to tonalite, locally coarsely porphyritic and muscovitic, southeastern New Hampshire.
Basalt (Cretaceous )
Basalt - Black, chiefly massive to porphyritic. Includes minor rhyolitic ignimbrite and andesitic tuff. Part of Ossipee Mountain Complex of Kingsley (1931)
Bethlehem Granodiorite (Early Devonian)
Bethlehem Granodiorite (Bethlehem Gneiss of Billings, 1955) - Gray, strongly foliated biotite-muscovite granodiorite and associated tonalite and granite.
Clough Quartzite (Lower Silurian (upper Llandoverian))
Clough Quartzite - Orthoquartzite, quartz metaconglomerate, muscovite schist, minor polymictic metaconglomerate. Disconformable below Fitch Formation and unconformable on Ordovician formations. Equivalent, in part, to member C of Rangeley Formation of Maine. Fossiliferous.
Exeter Diorite (Early Devonian)
Exeter Diorite - Includes associated intrusive rocks of southeastern New Hampshire; pyroxene and pyroxene-hornblende diorite and gabbro, along with minor granodiorite and granite.
Fitch and Clough Formations, undivided (Silurian)
Fitch and Clough Formations, undivided.
Fitch Formation (Upper Silurian; Pridolian and Ludlovian) (Upper Silurian - (Pridolian and Ludlovian))
Fitch Formation - Metamorphosed limestone, calcareous sandstone, siltstone, and dark pelitic schist; lower contact is disconformable on the Clough Quartzite. Fossiliferous.
Gile Mountain Formation, Interbedded gray slate or phyllite and brown-weathering calcite-ankerite metasiltstone (Lower Devonian)
Interbedded gray slate or phyllite and brown-weathering calcite-ankerite metasiltstone - Contains minor marble and quartzite. Resembles Waits River Formation in Vermont.
Gile Mountain Formation, undivided (Lower Devonian)
Gile Mountain Formation, undivided - Gray to tan metawacke and schist or phyllite; gradational into Meetinghouse Slate Member but more thickly bedded and less pelitic than the member. Includes minor metavolcanic lentils.
Granite, granodiorite, and tonalite (Late Ordovician)
Granite, granodiorite, and tonalite.
Granite, granodiorite, and trondhjemite (Late Ordovician)
Granite, granodiorite, and trondhjemite.
Greenvale Cove Formation (Lower Silurian? )
Greenvale Cove Formation - Grayish-violet interlaminated metashale, feldspathic metasandstone, and calc-silicate rock of the Piermont allochthon in western New Hampshire.
Hornblende-biotite quartz monzodiorite (Jurassic)
Hornblende-biotite quartz monzodiorite - Composition ranges from quartz monzonite to diorite.
Hornblende granodiorite of Highlandcroft pluton (Late Ordovician)
Hornblende granodiorite of Highlandcroft pluton - Contains minor tonalite and diorite.
Hurricane Mountain Formation (Upper Cambrian?)
Hurricane Mountain Formation - Rusty-weathered, dark siliceous scaly slate or schist of flaser structure, polymictic fragments from a few mm to (in Maine) several hundred meters. A melange consisting of metasedimentary, felsic/mafic metavolcanics, and ultramafic rocks..
Hypersthene-biotite quartz diorite and hornblende or actinolite diorite or gabbro (Early Devonian - Late Devonian)
Hypersthene-biotite quartz diorite and hornblende or actinolite diorite or gabbro - Spatially associated with Spaulding Tonalite plutons.
Kinsman Granodiorite (Early Devonian )
Kinsman Granodiorite - (Kinsman Quartz Monzonite of Billings, 1955) - Foliated granite, granodiorite, tonalite, and minor quartz diorite; large megacrysts of potassium feldspar characteristic; garnet locally abundant.
Littleton Formation, Lower unnamed member (Lower Devonian)
Littleton Formation, Lower unnamed member - Thinly or poorly bedded aluminous lower part, somewhat rusty. Rare quartzite lentils. Carrabassett Formation in northwestern Maine is probably correlative.
Lower part of Rangeley Formation (Lower Silurian (Llandoverian))
Lower part of Rangeley Formation - Gray, thinly laminated (5-25 mm) metapelite with local lentils of turbidites and thin quartz conglomerates in western New Hampshire. Sparse calc-silicate pods and coticule. Probably equivalent to member B of Rangeley Formation of Maine.
Madrid and Smalls Falls Formations, undivided (Silurian)
Madrid and Smalls Falls Formations, undivided.
Madrid Formation (Upper Silurian? )
Madrid Formation - Massive to weakly foliated, purple biotite-feldspar granofels, layered calc-silicate, and dark pelitic-sulfidic schist containing calc-silicate pods in upper member; an eastern facies equivalent to the upper part of the Fitch Formation. Locally mapped as the Warner Formation of Nielson (1981) in southern New Hampshire.
Massabesic Gneiss Complex (Late Proterozoic)
Massabesic Gneiss Complex - Migmatite consisting of pink, foliated biotite granite intruding gneissic and granulose metasedimentary and metavolcanic rocks in southeastern New Hampshire.
Massabesic Gneiss Complex (Late Proterozoic)
Massabesic Gneiss Complex - Quartzose-feldspathic gneiss and biotite schists (locally rusty), granofels, and cal-silicate rocks closely intruded by, and grading into, a pink gneissic granite (623 Ma) that produced a migmatite.
Member C (uppermost) of the Rangeley Formation in Maine and northeastern and southwestern New Hampshire (Lower Silurian (Llandoverian))
Member C (uppermost) of the Rangeley Formation in Maine and northeastern and southwestern New Hampshire - Quartz-pebble conglomerate overlain by rusty metapelite and feldspathic quartzite.
Merrimack Group, Berwick Formation (Ordovician? - Silurian?)
Merrimack Group, Berwick Formation - Purple biotite-quartz-feldspar granofels or schist and interbeds of calc-silicate granofels and minor metapelites. Stratigraphic sequence with respect to Eliot Formation uncertain
Merrimack Group, Berwick Formation, Unnamed member (Ordovician? - Silurian?)
Merrimack Group, Berwick Formation, Unnamed member - Contains more calc-silicate (15 percent) than does the remainder of the formation (5 percent).
Merrimack Group, Eliot Formation (Ordovician? - Silurian?)
Merrimack Group, Eliot Formation - Gray to green phyllite, calcareous quartzite, quartz-mica schist, and well-bedded calc-silicate.
Moat Volcanics (Middle Jurassic?)
Moat Volcanics - Bedded and ignimbritic tuffs, flows, and breccias; also porphyritic rhyolite and minor trachyte.
Partridge Formation, undivided (Middle - Upper Ordovician)
Partridge Formation, undivided - Black, rusty-weathering sulfidic-graphitic slate or schist and sparse to abundant metagraywacke. Lies stratigraphically between upper and lower parts of the Ammonoosuc Volcanics.
Perry Mountain and Rangeley Formations, undivided (Silurian)
Perry Mountain and Rangeley Formations, undivided.
Perry Mountain Formation, Sedimentary and subordinate distal felsic and mafic volcanic facies in Piermont allochthon (Lower?- Middle? Silurian)
Perry Mountain Formation, Sedimentary and subordinate distal felsic and mafic volcanic facies in Piermont allochthon.
Perry Mountain Formation, undivided (Lower? - Middle? Silurian)
Perry Mountain Formation, undivided - Sharply interbedded quartzites, light-gray nongraphitic metapelite, and "fast-graded" meta-turbidites. Coticule layers common.
Rangeley Formation, undivided (Lower Silurian (Llandoverian))
Rangeley Formation, undivided.
Rhyolite and fine-grained granite (Cretaceous)
Rhyolite and fine-grained granite - Includes some ignimbritic caldera-fill and minor intrusive rocks (part of Ossipee Mountain Complex of Kingsley, 1931); also some aphanitic gray, black, or tan quartz-feldspar porphyry.
Rye Complex (Ordovician? - Late Proterozoic?)
Rye Complex - Migmatite of gray, foliated, sheared or mylonitized two-mica granite and pegmatite, minor hornblende-biotite diorite, intruding metapelites and metavolcanic rocks in southeastern New Hampshire.
Rye Complex (Ordovician? - Late Proterozoic?)
Rye Complex - Light-colored to gray schists and gneisses, quartzites, and amphibolites. Variably migmatized and mylonized. Contact with Kittery Formation on west is the Portsmouth Fault.
Rye Complex, Breakfast Hill Granite of Novotny (1964). (Ordovician? - Late Proterozoic? )
Breakfast Hill Granite of Novotny (1964) - Blastomylonitic quartz-feldspar granitic gneiss and pegmatite intruded the Rye Complex and formed a migmatite.
Spaulding Tonalite (Early Devonian)
Spaulding Tonalite (Spaulding Quartz Diorite of Fowler-Billings, 1949) - Weakly foliated to nonfoliated, spotted biotite quartz diorite, tonalite, granodiorite, and granite; garnet and muscovite may or may not be present.
Tonalite, diorite, granodiorite, and granite (Late Ordovician )
Tonalite, diorite, granodiorite, and granite - More mafic rocks have hornblende; part of Lost Nation pluton.
Upper part of Rangeley Formation (Lower Silurian (Llandoverian))
Upper part of Rangeley Formation - Rusty-weathering, pelitic schist, metasandstone, and local coarse-grained metasandstone lentils; calc-silicate pods common; minor coticule. Probably equivalent to member C of Rangeley Formation of Maine.
Winnipesaukee Tonalite (Early Devonian)
Winnipesaukee Tonalite (Winnipesaukee Quartz Diorite of Billings, 1955) - Gray, massive to foliated tonalite and minor quartz diorite, granodiorite, and granite. Probably coeval with Spaulding Tonalite.
New Jersey
Allentown Dolomite (Lower Ordovician and Upper Cambrian)
Allentown Dolomite (Wherry, 1909) - Very thin to very thick bedded dolomite containing minor orthoquartzite and shale. Upper part is medium-light- to medium-dark-gray, fine- to medium-grained, locally coarse-grained, medium- to very thick bedded dolomite. Floating quartz sand grains and two sequences of medium-light- to very light gray, thin-bedded quartzite and discontinuous, dark-gray chert lenses occur directly below upper contact. Rhythmically bedded lower dolomite beds alternate between light and dark gray weathering, medium and very light gray, fine and medium grained, and thin and medium bedded, which are interbedded with shaly dolomite. Ripple marks, crossbeds, edgewise conglomerate, mud cracks, oolites, and algal stromatolites occur throughout unit, but more typically in lower part. Shaly dolomite increases downward toward lower conformable contact with the Leithsville Formation. Oldest beds contain trilobite fauna of early Late Cambrian age; younger beds contain latest Cambrian fauna (Howell, 1945; Howell and others, 1950). Thickness about 580 m (1,900 ft).
Allentown Dolomite (Lower Ordovician and Upper Cambrian) (Wherry, 1909) (Lower Ordovician and Upper Cambrian)
Allentown Dolomite (Lowest Lower Ordovician and Upper Cambrian) (Wherry, 1909) - Medium- to very light gray, fine- to medium-grained, very thin to very thick bedded dolomite containing minor orthoquartzite and shale. Oolites and algal stromatolites occur throughout unit. Shaly dolomite increases downward towards lower conformable contact with the Leithsville Formation. Unit does not crop out but is known from subsurface borings near Flanders (Volkert and others, 1990). Thickness ranges from 0 to 73 m (0-240 ft) due to erosion.
Beekmantown Group, Lower Part (Lower Ordovician)
Beekmantown Group, Lower Part (Clarke and Schuchert, 1899) - Very thin to thick-bedded, interbedded dolomite and minor limestone. Upper beds are light-olive-gray to dark-gray, fine- to medium-grained, thin- to thick-bedded dolomite. Middle part is olivegray-, light-brown-, or dark-yellowish-orange- weathering, dark-gray, aphanitic to fine-grained, laminated to medium-bedded dolomite and light-gray to light-bluish-gray-weathering, medium-dark- to dark-gray, fine-grained, thin- to medium-bedded limestone, that is characterized by mottling with reticulate dolomite and light-olive-gray to grayish-orange, dolomitic shale laminae surrounding limestone lenses. Limestone grades laterally and down section into medium- gray, fine-grained dolomite. Lower beds consist of medium-light- to dark-gray, aphanitic to coarse-grained, laminated to medium-bedded, locally slightly fetid dolomite having thin black chert beds, quartz-sand laminae, and oolites. Lenses of light-gray, very coarse to coarse-grained dolomite and floating quartz sand grains and quartz-sand stringers at base of sequence. Lower contact placed at top of distinctive medium-gray quartzite. Contains conodonts of Cordylodus proavus to Rossodus manitouensis zones of North American Midcontinent province as used by Sweet and Bergstrom (1986). Unit Obl forms Stonehenge Formation of Drake and Lyttle (1985) and Drake and others (1985), upper and middle beds are included in Epler Formation, and lower beds are in Rickenbach Dolomite of Markewicz and Dalton (1977). Unit is about 183 m (600 ft) thick.
Belleplain Member of the Kirkwood Formation (middle Miocene, Serravallian)
Belleplain Member - Clay to silty clay at the base and sand at the top. Clay, massive to laminated, gray-brown, locally contains abundant diatoms and scattered small shell fragments. Sand, fine- to medium-grained, pale-gray to white, somewhat micaceous and woody with scattered shell fragments. Most Belleplain sand is quartz with lesser amounts of feldspar and mica. Pyrite is common in clayey strata. The Belleplain subcrops beneath surficial deposits where the overlying Cohansey Formation was eroded away. Along the Atlantic Ocean, the member is exposed on the southern sheet between Beach Haven Terrace, Ocean County, and Brigantine, Atlantic County, where the unit is overlain by thin to thick deposits of alluvium. The member is as much as 15 m (49 ft) thick. The basal contact with the underlying Wildwood Member is sharp and unconformable with a thin bed of reworked coarse-grained quartz sand at the base. A middle Miocene age for the Belleplain was determined from diatoms. Specifics of the diatom biostratigraphy are discussed in the Description of Subsurface Units. Shells from this unit had a strontium-isotope age estimate of 13.2 Ma (Sugarman and others, 1993).
Bellvale Sandstone (Middle Devonian)
Bellvale Sandstone (Bellvale Flags of Darton, 1894; Willard, 1937) - Upper beds are grayish-red to grayish-purple sandstone containing quartz pebbles as large as 3 cm (1.2 in) in diameter. Lower beds are light-olive-gray- to yellowish-gray- and greenish-black-weathering, medium-gray to medium-bluish-gray very thin to very thick bedded siltstone and sandstone cross-bedded, graded and interbedded with black to dark-gray shale that is locally fossiliferous. More sandstone in upper beds becomes finer downward. Lower contact conformable and placed where beds thicken and volume of shale and siltstone are about equal. The unit is 535 to 610 m (1,750-2,000 ft) thick.
Berkshire Valley and Poxono Island Formations, undivided (Upper Silurian)
Berkshire Valley and Poxono Island Formations, undivided - Thickness ranges from 76 m (250 ft) at Greenwood Lake to 122 m (400 ft) in Longwood Valley. Berkshire Valley Formation (Barnett, 1970) - Commonly yellowish-gray weathering, medium-gray to pinkish-gray, very thin to thin-bedded fossiliferous limestone interbedded with gray to greenish-gray calcareous siltstone and silty dolomite, medium-gray to light-gray dolomite conglomerate, and grayish-black, thinly laminated shale. Lower contact conformable. Thickness ranges from 27 to 38 m (90-125 ft) thick. Poxono Island Formation, (White, 1882; Barnett, 1970) - Very thin to medium-bedded sequence of medium-gray, greenish-gray, or yellowish-gray, mud-cracked dolomite; light-green, pitted, medium-grained calcareous sandstone, siltstone, and edgewise conglomerate containing gray dolomite; and quartz-pebble conglomerate containing angular to subangular pebbles as much as 2 cm (0.8 in.) long. Interbedded grayish-green shales at lower contact are transitional into underlying Longwood Shale. Thickness ranges from 49 to 84 m (160-275 ft) thick.
Bloomsburg Red Beds (Upper Silurian)
Bloomsburg Red Beds (White, 1883) (High Falls Shale of previous usage) - Grayish-red, thin- to thick-bedded, poorly to moderately well sorted, massive siltstone, sandstone, and local quartz-pebble conglomerate containing local planar to trough crossbedded laminations. Conglomerate consists of matrix-supported quartz pebbles in grayish-red, fine-grained sandstone matrix. Locally, near base of unit, is greenish-gray, light-gray, or grayish-orange, massive, planar tabular to trough crossbedded quartz sandstone to siltstone with subrounded grains. Lower part of formation marked by several upward-fining sequences of light-gray sandstone grading through grayish-red, fine-grained sandstone and siltstone to grayish-red, mudcracked siltstone and mudstone. Each sequence is 1 to 3 m (3-10 ft) thick. Lower contact placed at bottom of lowermost red sandstone. Thickness approximately 460 m (1,510 ft).
Boonton Formation (Lower Jurassic)
Boonton Formation (Olsen, 1980) - Reddish-brown to brownish-purple, fine-grained sandstone, siltstone, and mudstone; sandstone commonly micaceous, interbedded with siltstone and mudstone in fining-upward sequences mostly 1.5 to 4 m (5-13 ft) thick. Red, gray and brownish-purple siltstone and black, blocky, partly dolomitic siltstone and shale common in lower part. Irregular mudcracks, symmetrical ripple marks, and burrows, as well as gypsum, glauberite, and halite pseudomorphs are abundant in red mudstone and siltstone. Gray, fine-grained sandstone may have carbonized plant remains and reptile footprints in middle and upper parts of unit. Near Morristown, beds of quartz-pebble conglomerate (unit Jbcq) as much as 0.5 m (1.6 ft) thick interfinger with beds of sandstone, siltstone, and shale. Northeast of Boonton, beds of quartz-pebble conglomerate (not mapped separately as Jbcq) occur locally with conglomerate containing abundant clasts of gneiss and granite in matrix of reddish-brown sandstone and siltstone. Maximum thickness is about 500 m (1,640 ft).
Bushkill Member (Middle Ordovician)
Bushkill Member (Drake and Epstein, 1967) - Interbedded medium- to dark gray, thinly laminated to thick-bedded shale and slate and less abundant medium-gray to brownish-gray, laminated to thin-bedded siltstone. To the southwest, fine-grained, thin dolomite lenses occur near base. Complete turbidite sequences (Bouma, 1962) occur locally, but basal cutout sequences (Tbcde, Tcde or Tde) dominate. Conformable lower contact is placed at top of highest shaly limestone; elsewhere, lower contact is commonly strain slipped. Correlates with graptolite Climacograptus bicornis to Corynoides americanus zones of Riva (1969, 1974) (Parris and Cruikshank, 1992). Thickness ranges from 1,250 m (4,100 ft) in Delaware River Valley to 457 m (1,500 ft) at New York State line.
Cheesequake Formation (Upper Cretaceous, lower Campanian and upper Santonian)
Cheesequake Formation - New unit named herein for outcrops in gullies at Cheesequake in the eastern part of the South Amboy 7.5-min quadrangle. Basal sand, quartz and glauconite, fine-grained, clayey, thin-bedded, dark-greenish-gray; middle part, quartz sand, very fine grained, thick-bedded, dark-gray, micaceous, and clayey silt with scattered and varying amounts of glauconite sand; upper part, quartz sand, fine-grained, clayey, thinbedded. Sand, excluding glauconite sand beds, is primarily quartz with small amounts of feldspar and mica. In most areas, particularly in the updip sections, the upper sand has been eroded away. This formation underlies most of the map area and is as much as 43 m (141 ft) thick. Nannofossils obtained from the Toms River and Freehold drillholes indicate that the Cheesequake Formation is latest Santonian at the base to earliest Campanian at the top (P.C. Valentine, oral commun., 1989) or equivalent to Zones CC16 to CC17. Thus the Santonian-Campanian boundary lies within the Cheesequake Formation. Studies of pollen (Litwin and others, 1993) in outcrop indicate a pollen assemblage containing elements of the ?Pseudoplicapollis cuneata-Semioculopollis verrucosa Zone (Vc of Christopher, 1982) and the CA2 Zone of Wolfe (1976).
Cheesequake Formation (Upper Cretaceous, lower Campanian and upper Santonian)
Cheesequake Formation - Clay and clay-silt, micaceous, thin-bedded to laminated, dark-gray; weathers light tan. Contains abundant wood fragments intercalated with light-colored, fine-grained micaceous quartz sand and is rarely crossbedded. Rock fragments and feldspar are minor sand constituents. Small cylindrical burrows occur in the updip area. Abundant, rounded, pale-gray siderite concretions (about 8 cm (3 in) in diameter) occur in thin discontinuous beds. Sand interfingers rapidly within a short distance with extensively bioturbated, dark-gray, very micaceous, somewhat woody clay-silt. The basal clay-silt has extensive cylindrical burrows filled with fine-grained, light- to medium-green botryoidal glauconite. The basal contact with the underlying Magothy Formation is sharp. Reworked siderite concretions and some glauconite and coarse-grained quartz sand are found along the contact within the Cheesequake. Unit exposed only in the South Amboy and Keyport quadrangles. The unit is about 14 m (46 ft) thick. The age of the Cheesequake was determined from pollen (Litwin and others, 1993), which indicates the unit is between the Merchantville Formation microflora (CA2 Zone of Wolfe, 1976, lower Campanian) and the uppermost Magothy microflora (?Pseudoplicapollis cunceata-Semioculopollis verrucosa Zone of Christopher, 1979, upper Santonian). It is probable that the Cheesequake Formation contains the Santonian-Campanian boundary. This unit was not recognized by Petters (1976) who concluded that the Magothy and Merchantville interfingered in the subsurface and the Merchantville was, in part, Santonian.
Chestnut Hill Formation (Late Proterozoic)
Chestnut Hill Formation (Drake, 1984) - Interbedded arkose, ferruginous quartzite, quartzite conglomerate, metarhyolite, and metasaprolite. Confined to a few small areas north and east of Phillipsburg, on the western side of Bowling Green Mountain, northwest of High Bridge, and a few areas too small to show at this map scale.
Coeymans Formation, Kalkberg Limestone, Coeymans Limestone, Manlius Limestone, undivided (Lower Devonian)
Coeymans Formation, Kalkberg Limestone, Coeymans Limestone, Manlius Limestone, undivided - At New York border consists of fine-grained, chert-bearing, argillaceous limestone (Kalkberg Limestone) grading downward through coarse-grained limestone (Coeymans Limestone) into fine-grained limestone (Manlius Limestone). Toward southwest these units grade into fine- to coarse-grained limestone with a marked increase in quartz sand that comprises the Coeymans Formation (Epstein and others, 1967). Total thickness 27 m (90 ft). Coeymans Formation (Epstein and others, 1967) - Medium-light-gray, fine- to coarse-grained calcareous sandstone and medium-gray, fine- to coarse-grained, medium- to thick-bedded, locally irregularly-bedded, argillaceous to arenaceous limestone containing lenses of quartz sand and nodules of black chert. Grades downward into medium-gray, fine-grained, argillaceous and arenaceous limestone containing local beds of fine- to coarse-grained pebbly calcareous sandstone. Local bioherms consisting of light-gray to light-pinkish-gray, coarse-grained to very coarse biogenic limestone are unbedded and have sharp boundaries. Lower contact of unit abrupt. Formation thickness varies from 11 m (35 ft) in northeast to 24 m (80 ft) in southwest. Kalkberg Limestone (Chadwick, 1908) - Medium-gray-weathering, medium-dark-gray, fine-grained, very thin to massively bedded fossiliferous limestone. Grades downward into fine- to medium-grained, thin-bedded, fossiliferous argillaceous limestone containing nodules and lenses of dark-gray chert. Grades to the southwest into calcareous and arenaceous rocks of the upper part of the Coeymans Formation near Wallpack Center. Lower contact placed at base of lowest black chert. Approximately 12 m (40 ft) thick. Coeymans Limestone (Clarke and Schuchert, 1899) - Medium-gray weathering, medium-dark-gray, fine-to-coarse-grained, medium- to massively bedded fossiliferous limestone and local argillaceous limestone lenses. Unit is approximately 9 m (30 ft) thick. Between Duttonville and Millville, grades into biohermal and nonbiohermal facies of medium- to coarse-grained limestone of Coeymans Formation of Epstein and others (1967). Manlius Limestone (Vanuxem, 1840) - Medium-gray weathering, medium-dark- to dark-gray, very fine to fine-grained, unevenly bedded fossiliferous limestone. Some local medium-grained limestone, yellowish-gray shale partings and biostromes. Near Hainesville, unit grades into lower part of Coeymans Formation. Lower contact abrupt and placed at top of uppermost very fine grained argillaceous limestone. Thickness approximately 11 m (35 ft).
Cohansey Formation (Middle Miocene, Serravallian)
Cohansey Formation - Sand, white to yellow with local gravel and clay. Locally stained red or orange brown by iron oxides and (or) cemented into large blocks of ironstone. Unweathered clay is typically dark gray, but commonly weathers white where interbedded with thin beds of ironstone. Unit is a complex of interfingering marine and nonmarine facies. Sand is typically medium grained and moderately sorted although it ranges from fine to very coarse grained and from poorly to well sorted. Sand consists of quartz and siliceous rock fragments. Some beds are locally micaceous, and in the Lakehurst area, Ocean County, some beds have high concentrations of "black" sand (pseudorutile) that was once extensively mined. In general, the sand is crossbedded, although the style of crossbedding varies significantly with the paleoenvironment. Trough crossbedding predominates, especially in the nonmarine channel fill deposits, and the scale of the crossbeds varies from small to large. In some areas, planar bedding is well developed in sections that have abundant marine burrows (mostly the clay-lined trace fossil Ophiomorpha nodosa). Such marine-influenced beds (largely foreshore deposits) occur on the central sheet west of Asbury Park, near Adelphia, Monmouth County, north of the Lakehurst Naval Air Station, Ocean County, and at Juliustown, Burlington County (Owens and Sohl, 1969), and on the southern sheet as far north as Salem, Salem County. Gravel beds occur locally, especially in updip areas such as near New Egypt, Ocean County, in the Atlantic Highlands and in the highlands west of Barnegat, Ocean County, in the southern part of the central sheet and in mixed marine and nonmarine facies in the northeastern part of the southern sheet where gravel occurs in well-defined channels. Most of the gravel is 1.3 to 2.5 cm (0.5-1.0 in) in diameter, but pieces as long as 10 cm (4 in) are present. The gravel is composed of quartz with small amounts of black chert and quartzite. Clay commonly occurs as discrete, thin, discontinuous beds, is dark gray where unweathered, white or red where weathered. Lesser, thin laminated clay strata also are present. Locally, as near Lakehurst, thick, dark-gray, very lignitic clay was uncovered during the mining of ilmenite and is informally called the Legler lignite (Rachele, 1976). An extensive, well-preserved leaf flora was collected from a thick clay lens in a pit near Millville, Cumberland County. The leaf flora was dominated by Alangium sp., a tree no longer growing in eastern North America (J.A. Wolfe, written commun., 1992). Maximum thickness in the map area is about 60 m (197 ft); however, thickness is difficult to determine because of the irregular basal contact and extensive post-depositional erosion. There is as much as 18 m (59 ft) of relief along the basal contact. The basal contact is sharp, undulatory, and directly overlain by a thin gravel bed. The Cohansey Formation unconformably overlies the Kirkwood Formation and is found in channels cut down into the Kirkwood. Where the Kirkwood consists of sandy, light-colored sediments, the basal contact of the Cohansey is drawn below crossbedded sediments. Where the Kirkwood consists of dark-colored silty beds, the basal contact is drawn between light-colored Cohansey sediments and the underlying dark-colored sediments. The Cohansey was markedly thinned because of erosion prior to deposition of overlying units in the western and southern parts of the southern sheet (Owens and Minard, 1975). The unit has been extensively eroded and stripped from large areas of the New Jersey Coastal Plain, particularly in the central sheet where outliers are common. In spite of its widespread nature, the Cohansey is poorly exposed because of its loose sandy composition, which causes it to erode easily (Newell and others, in press). Because of this same sandy nature, the Cohansey has been widely mined for sand, and manmade exposures are common in many areas. The age of the Cohansey is controversial because no calcareous microfauna or macrofauna have been found in this formation. The best indication of age comes from pollen and spores obtained from dark carbonaceous clay. Rachele (1976) analyzed the microflora from the Legler site and noted that the Cohansey had a rich and varied assemblage including several genera labeled "exotics" which no longer occur in the northeastern United States: Engelhardia, Pterocarya, Podocarpus, and Cyathea. Greller and Rachele (1984) estimated a middle Miocene age. Ager's (in Owens and others, 1988) analysis of the Cohansey from a corehole at Mays Landing also suggests a middle Miocene (Serravallian) age.
Feltville Formation (Lower Jurassic)
Feltville Formation - Mostly fine-grained, feldspathic sandstone, coarse siltstone, and silty mudstone, brownish-red to light-grayish-red. Fine-grained sandstone is moderately well sorted, cross laminated, and contains 15 percent or more feldspar; interbedded with mudstone, indistinctly laminated, bioturbated, and calcareous in places. A thin bed (0-2 m (0-7 ft) thick) of black, microlaminated carbonaceous limestone and gray calcareous mudstone occurs near the base and contains fish and plant fossils, and thermally mature hydrocarbons. Thickness of unit in the Sand Brook syncline is about 155 m (509 ft).
Feltville Formation (Lower Jurassic)
Feltville Formation (Olsen, 1980) - Interbedded brownish-red to light-grayish-red, fine- to coarse-grained sandstone, gray and black, coarse siltstone in upward-fining cycles, and silty mudstone. Fine-grained sandstone and siltstone are moderately well sorted, commonly cross-laminated, and have 15 percent or more feldspar; interbedded with brownish-red, indistinctly laminated, bioturbated calcareous mudstone. Thermally metamorphosed into hornfels where in contact with Preakness Basalt. Near the base are two thin, laterally continuous beds of black, carbonaceous limestone and gray, calcareous siltstone, each up to 3 m (10 ft) thick. These contain abundant fish, reptile, anthropod, and diagnostic plant fossils. Three or four, thin, gray to black siltstone and mudstone sequences occur in upper part of unit. Near Oakland, subrounded pebbles to cobbles of quartzite and quartz in a red siltstone and sandstone matrix (Jfc) interfinger with sandstone and siltstone of the Feltville Formation. Maximum thickness about 155 m (510 ft).
Feltville Formation Conglomerate and Sandstone facies (Lower Jurassic)
Feltville Formation Conglomerate and Sandstone facies - Near Oakland, subrounded pebbles to cobbles of quartzite and quartz in a red siltstone and sandstone matrix (Jfc) interfinger with sandstone and siltstone of the Feltville Formation.
Franklin Marble (Middle Proterozoic)
Franklin Marble - White- to light-gray-weathering, white, grayish-white, or, less commonly pinkish-orange, coarse- to locally fine-crystalline calcite marble with accessory amounts of graphite, phlogopite, chondrodite, clinopyroxene, and serpentine. Contains pods and layers of clinopyroxene-garnet skarn, hornblende skarn, and clinopyroxene-rich rock. Thin layers of metaquartzite occur locally. Intruded by the Mount Eve Granite in the Pochuck Mountain area. Franklin Marble is host to the Franklin and Sterling Hill zinc ore bodies; exploited for talc and asbestiform minerals near Easton, Pennsylvania. Subdivided into an upper marble, "Wildcat marble," and a lower marble, "Franklin marble," by New Jersey Zinc Co. geologists (Hague and others, 1956).
Gneiss granofels and Migmatite (Middle Proterozoic)
Gneiss granofels and Migmatite - Gneiss and granofels range in composition from felsic to intermediate to mafic; intermediate compositions predominate. Contains a wide variety of rock types including graphitic schist and marble. Many rocks were injected by a granitoid that has blue quartz and augen of potassic feldspar and are arteritic migmatites. One body of gneiss contains a 1 m by 0.5 m (3 by 2 ft) phacoid of gabbro that is interpreted to be an olistolith. Unit probably represents a sequence of meta-sedimentary and metavolcanic rocks that have been heavily injected and migmatized by felsic magma.
Green Pond Conglomerate (Lower (?) and Middle Silurian)
Green Pond Conglomerate (Rogers, 1836) - Medium- to coarse-grained quartz-pebble conglomerate, quartzitic arkose and orthoquartzite, and thin- to thick-bedded reddish-brown siltstone. Grades downward into gray, very dark-red, or grayish-purple, medium- to coarse-grained, thin- to very thick bedded pebble to cobble conglomerate containing clasts of red shale, siltstone, and chert; yellowish-gray sandstone and chert; dark-gray shale and chert; and white-gray and pink milky quartz. Quartz cobbles are as long as 10 cm (4 in.), and rare red shale clasts as much as 46 cm (18 in.) across. Milky quartz pebbles average 2.5 cm (1 in.) in length. Red arkosic quartz-pebble conglomerate and quartzite are more abundant than gray and grayish-green quartzite. Unconformably overlies Martinsburg Formation, Allentown Dolomite, Leithsville Formation, or Proterozoic rocks. About 305 m (1000 ft) thick.
Hardyston Quartzite (Lower Cambrian)
Hardyston Quartzite (Lower Cambrian) (Wolff and Brooks, 1898) - Light- to medium-gray and bluish-gray conglomeratic sandstone. Varies from pebble conglomerate, to fine-grained, well-cemented quartzite, to arkosic or dolomitic sandstone. Conglomerate contains subangular to subrounded white quartz pebbles up to 2.5 cm (1 in.). Lower contact unconformable. About 0 to 9 m (1-30 ft) thick.
Hardyston Quartzite (Lower Cambrian)
Hardyston Quartzite (Wolff and Brooks, 1898) - Medium- to light-gray, fine- to coarse-grained, medium- to thick-bedded quartzite, arkosic sandstone and dolomitic sandstone. Basal pebble to cobble conglomerate typically contains clasts of local basement affinities. Contains fragments of the trilobite Olenellus thompsoni of Early Cambrian age. Thickness approximately 0.5 to 62 m (1.6-200 ft).
High Point Member (Upper Ordovician)
High Point Member (Drake, 1991) - Medium-dark-gray, thin-bedded shale, siltstone and fine-grained sandstone, containing turbidite sequences Tbcde to Tcde of Bouma (1962). Interbedded with less abundant, light-yellowish-gray-weathering, medium-gray to medium-dark-gray, medium-grained, medium- to thick-bedded and massive, quartz- and calcareous-cemented quartz sandstone containing rip-ups of medium- to dark-gray shale and siltstone that commonly consist of Bouma (1962) turbidite sequences Tab to Ta. Restricted to northeast section of Martinsburg outcrop belt. Thermally metamorphosed near intrusive bodies. Grades along strike to the southwest into Ramseyburg Member by decrease in average grain size, absence of shale rip-ups, and lack of siliceous cement. Lower contact gradational and placed at base of lowermost thick-bedded graywacke or amalgamated graywacke containing shale rip-ups. Unit assigned to Orthograptus ruedemanni zone to Climacograptus spiniferus zone of Riva (1969, 1974) using graptolites collected by Parris and Cruikshank (1992). Thickness ranges from 0 to 1,370 m (0-4,500 ft).
Hornblende Granite (Middle Proterozoic)
Hornblende Granite - Pinkish-gray- to medium-buff-weathering, pinkish-white or light-pinkish-gray, medium- to coarse-grained, gneissoid to indistinctly foliated granite and sparse granite gneiss composed principally of microcline microperthite, quartz, oligoclase, and hornblende. Some phases are quartz syenite or quartz monzonite. Includes small bodies of pegmatite and amphibolite not shown on map. U-Pb age approximately 1,090 Ma (Drake and others, 1991b).
Hornblende Syenite (Middle Proterozoic)
Hornblende Syenite - Tan- to buff-weathering, pinkish-gray or greenish-gray, medium- to coarse-grained, gneissoid syenite and lesser amounts of quartz syenite containing microcline microperthite, oligoclase, quartz, and hornblende. Some phases are monzonite or monzodiorite.
Jacksonburg Limestone and Sequence at Wantage, undivided (Middle Ordovician)
Jacksonburg Limestone and Sequence at Wantage, undivided - Jacksonburg Limestone - Upper part is medium- to dark-gray, laminated to thin-bedded shaly limestone and less abundant medium-gray arenaceous limestone containing quartz-sand lenses. Upper part thin to absent to northeast. Lower part is interbedded medium- to dark-gray, fine- to medium-grained, very thin to medium-bedded fossiliferous limestone and minor medium- to thick-bedded dolomite-cobble conglomerate having a limestone matrix. Unconformable on Beekmantown Group and conformable on the discontinuous sequence at Wantage in the Paulins Kill area. Contains conodonts of North American midcontinent province from Phragmodus undatus to Aphelognathus shatzeri zones of Sweet and Bergstrom (1986). Thickness ranges from 41 to 244m (135-800 ft). Sequence at Wantage - Restricted, discontinuous sequence of interbedded limestone, dolomite, conglomerate, siltstone, and shale. Upper part is medium-yellowish-brown- to olive-gray-weathering, medium- to dark-gray, very fine to fine-grained, laminated to massive limestone and dolomite that grade down into underlying clastic rocks of lower part. Upper part locally absent. Lower part ranges from grayish-red, medium-gray, pale-brown, and greenish-gray to pale-green mudstone and siltstone containing disseminated subangular to subrounded chert-gravel, quartz-sand lenses, and chert-pebble conglomerate. Lower contact unconformable. Thickness ranges from 0 to 46 m (0-150 ft).
Jutland Klippe Sequence, undifferentiated (Middle Ordovician to Upper Cambrian?)
Jutland Klippe Sequence, undifferentiated - Rocks of the Jutland klippe sequence occur in six isolated fragments of the Jutland klippe east of Jutland and two fragments of the Peapack klippe along the Peapack-Ralston fault in the New Jersey Highlands hinterland. The sequence is largely varicolored shale and sandstone, but contains lesser amounts of limestone, dolomite and pebble conglomerate. Lash and Drake (1984) correlate this sequence with the accretionary prism deposits of the Greenwich slice of the Hamburg klippe in eastern Pennsylvania. Rocks of the Jutland klippe sequence were folded and thrust over rocks of the Kittatinny Valley sequence during the Taconic orogeny and then were deformed during the Alleghanian orogeny and again during Mesozoic rifting of eastern North America.
Jutland Klippe Sequence Unit A (lower Middle Ordovician to Upper Cambrian)
Jutland Klippe Sequence Unit A of Perissoratis and others (1979) - Interbedded red, green, and tan shale, sandstone, and dark-gray, aphanitic to fine-grained limestone, which contains floating quartz-sand grains. Grades downward through interbedded sequence of red, green and brown shale to medium-gray to brown, fine- to coarse-grained sandstone and quartz-pebble conglomerate. Lower beds are dark-gray shale and siltstone containing minor dark-gray, aphanitic to fine-grained, medium-bedded limestone. Lower contact is a fault. Contains graptolites in the span of Anisograptus to Isograptus caduceus of Berry (1968) (Perissoratis and others, 1979) and conodonts of the Cordylodus proavus to Paroistodus proteus faunas of the North Atlantic Realm. Thickness is unknown.
Jutland Klippe Sequence Unit B (Middle Ordovician)
Jutland Klippe Sequence Unit B of Perissoratis and others (1979) - Heterogeneous sequence of interbedded red, green, tan and gray shale; interlaminated dolomite and shale; interbedded fine-grained graywacke siltstone and beds or lenses of sandstone; light-gray to pale-pinkish-gray quartzite; and interbedded fine-grained, thin-bedded limestone and red and green shale. Limestone locally resembles an intraformational conglomerate because it is disrupted, boudinaged, and surrounded by shale beds. Lower contact gradational and within interbedded sequence of thin- to medium-bedded sandstone, siltstone, and limestone. Perissoratis and others (1979) placed this contact at boundary between graptolite faunas Isograptus caduceus and Paraglossograptus etheridgei of Berry (1968). The youngest graptolites occur within Climacograptus bicornis zone of Berry (1968). Some shale beds contain conodonts (Ethington and others, 1958; Karklins and Repetski, 1989) and brachiopod fragments. Carbonate and pelitic rocks locally contain conodonts of Prioniodus triangularis to Pygodus anserinus faunas of North Atlantic Realm. Thickness varies due to structural complexity, but may be about 460 to 550 m (1,500-1,800 ft).
Kanouse and Esopus Formations and Connelly Conglomerate, undivided (Lower Devonian)
Kanouse and Esopus Formations and Connelly Conglomerate, undivided - Kanouse Sandstone (Kummel, 1908) - Medium-gray, light-brown, and grayish-red, fine- to coarse-grained, thin- to thick-bedded sparsely fossiliferous sandstone and pebble conglomerate. Basal conglomerate beds are interbedded with siltstone similar to the upper part of the Esopus Formation and contain well-sorted, subangular to subrounded, gray and white quartz pebbles less than 1 cm (0.4 in.) long. Lower contact gradational. About 14 m (46 ft) thick. Esopus Formation - (Vanuxem, 1842; Boucot, 1959) - Light- to dark-gray, laminated to thin-bedded siltstone interbedded with dark-gray to black mudstone, dusky-blue sandstone and siltstone, and yellowish-gray fossiliferous siltstone and sandstone. Lower contact probably conformable with the Connelly Conglomerate. The formation is about 100 m (330 ft) thick at Greenwood Lake and estimated at 55 m (180 ft) thick in Longwood Valley. Connelly Conglomerate (Chadwick, 1908) - Grayish-orange weathering, very light gray to yellowish-gray, thin-bedded quartz-pebble conglomerate. Quartz pebbles average 1 to 2 cm (0.4-0.8 in.), are subrounded to well rounded, and well sorted. The unit unconformably overlies the Berkshire Valley Formation. About 11 m (36 ft) thick.
Lamprophyre, tinguaite (phonolite with acicular acmite crystals), phonolite, bostonite (trachyte), and malignite (mafic nepheline syenite), undifferentiated (Silurian - Ordovician)
Lamprophyre, tinguaite (phonolite with acicular acmite crystals), phonolite, bostonite (trachyte), and malignite (mafic nepheline syenite), undifferentiated - Light-medium- to medium-dark-gray, aphanitic to fine-grained, alkalic to calcic-alkalic dikes and sills. Unit intrudes rocks from the Middle Proterozoic to the High Point Member of the Martinsburg Formation, but does not intrude the Shawangunk Formation. K-Ar data of 422 +/- 14 Ma from biotite phenocrysts in a minette (lamprophyre with biotite phenocrysts) dike (Charles Milton, written communication, 1972) suggests an Early Silurian age for some of these rocks.
Leithsville Formation (Middle and Lower Cambrian)
Leithsville Formation (Wherry, 1909) - Thin- to thick-bedded dolomite containing subordinate siliciclastic rocks. Upper part is medium- to medium-dark-gray, fine- to medium-grained, pitted, friable, mottled and massive dolomite. Middle part is medium-gray, stylolitic, fine-grained, thin- to medium-bedded dolomite that is interbedded with shaly dolomite and, less commonly, vari-colored quartz sandstone, siltstone, and shale. Lower part is medium-gray, medium-grained, medium-bedded dolomite containing quartz-sand grains in stringers and lenses near the contact with the Hardyston Quartzite. Archaeocyathids of Early Cambrian age suggest an intraformational disconformity separating rocks of Middle and Early Cambrian age (Palmer and Rozanov, 1976). Thickness approximately 305 m (1,000 ft).
Leithsville Formation (Middle and Lower Cambrian)
Leithsville Formation (Middle and Lower Cambrian) (Wherry, 1909) - Light- to dark-gray and lightolive-gray, fine- to medium-grained, thin- to medium-bedded dolomite. Grades downward through medium-gray, grayish-yellow, or pinkish-gray dolomite and dolomitic sandstone, siltstone and shale to medium-gray, medium-grained, medium-bedded dolomite containing quartz sand grains as stringers and lenses near the base. Lower contact gradational. Thickness ranges from 0 to 56 m (0-185 ft) due to erosion.
Lockatong Formation (Upper Triassic)
Lockatong Formation (Kummel, 1897) - Cyclically-deposited sequences consisting of light- to dark-gray, greenish-gray, and black, dolomitic or analcime-bearing silty argillite, laminated mudstone, silty to calcareous, argillaceous, very-fine-grained pyritic sandstone and siltstone, and minor silty limestone (Trl). Grayish-red, grayish-purple, and dark-brownish-red sequences (Trlr) common in upper half. Two types of cycles are recognized: detrital and chemical. Detrital cycles average 5.2 m (17 ft) thick and consist of basal, argillaceous, very fine grained sandstone to coarse siltstone; medial, dark-gray to black, laminated siltstone, silty mudstone, or silty limestone; and upper, light- to dark-gray, silty to dolomitic or analcime-rich mudstone, argillitic siltstone, or very-fine-grained sandstone. Chemical cycles are similar to detrital cycles, but thinner, averaging 3.2 m (10.5 ft). Cycles in northern Newark basin are thinner and have arkosic sandstone in lower and upper parts. Upper part of formation in northern basin composed mostly of light-gray to light-pinkish-gray or light-brown, coarse- to fine-grained, thick- to massive-bedded arkosic sandstone (Trla). Thermally metamorphosed into hornfels where intruded by diabase (Jd). Interfingers laterally and gradationally with quartz sandstone and conglomerate (Trls) and quartzite conglomerate (Trlcq) near Triassic border fault in southwestern area of map. Maximum thickness of Lockatong Formation about 1,070 m (3,510 ft).
Lockatong Formation (Upper Triassic)
Lockatong Formation - Predominantly cyclic lacustrine sequences of silty, dolomitic or analcime-bearing argillite; laminated mudstone; silty to calcareous, argillaceous very fine grained sandstone and pyritic siltstone; and minor silty limestone, mostly light- to dark-gray, greenishgray, and black. Grayish-red, grayish-purple, and dark-brownish-red sequences (Trlr) occur in some places, especially in upper half. Two types of cycles are recognized: freshwater-lake (detrital) and alkaline-lake (chemical) cycles. Freshwater-lake cycles average 5.2 m (17 ft) thick. They consist of basal, transgressive, fluvial to lake-margin deposits that are argillaceous, very fine grained sandstone to coarse siltstone with indistinct lamination, planar or cross lamination, or are disrupted by convolute bedding, desiccation cracks, root casts, soil-ped casts, and tubes. Medial lake-bottom deposits are laminated siltstones, silty mudstones, or silty limestones that are dark gray to black with calcite laminae and grains and lenses, or streaks of pyrite; fossils are common, including fish scales and articulated fish, conchostracans, plants, spores, and pollen. Upper regressive lake margin, playa lake, and mudflat deposits are light- to dark-gray silty mudstone to argillitic siltstone or very fine grained sandstone, mostly thick bedded to massive, with desiccation cracks, intraformational breccias, faint wavy laminations, burrows, euhedral pyrite grains, and dolomite or calcite specks. Alkaline-lake cycles are similar to freshwater-lake cycles, but are thinner, averaging 3 m (10 ft), have fewer fossils (mainly conchostracans), and commonly have red beds, extensive desiccation features, and abundant analcime and dolomite specks in the upper parts of cycles. Thickness near Byram is about 1,070 m (3,510 ft). The formation thins to the southeast and northeast; thickness near Princeton is less than 700 m (2,297 ft).
Lockatong Formation red bed (Upper Triassic)
Lockatong Formation red bed - Cyclically-deposited sequences consisting of light- to dark-gray, greenish-gray, and black, dolomitic or analcime-bearing silty argillite, laminated mudstone, silty to calcareous, argillaceous, very-fine-grained pyritic sandstone and siltstone, and minor silty limestone (Trl). Grayish-red, grayish-purple, and dark-brownish-red sequences (Trlr) common in upper half.
Lockatong Formation red bed (Upper Triassic)
Lockatong Formation red bed - Predominantly cyclic lacustrine sequences of silty, dolomitic or analcime-bearing argillite; laminated mudstone; silty to calcareous, argillaceous very fine grained sandstone and pyritic siltstone; and minor silty limestone, mostly light- to dark-gray, greenishgray, and black. Grayish-red, grayish-purple, and dark-brownish-red sequences (Trlr) occur in some places, especially in upper half. Two types of cycles are recognized: freshwater-lake (detrital) and alkaline-lake (chemical) cycles. Freshwater-lake cycles average 5.2 m (17 ft) thick. They consist of basal, transgressive, fluvial to lake-margin deposits that are argillaceous, very fine grained sandstone to coarse siltstone with indistinct lamination, planar or cross lamination, or are disrupted by convolute bedding, desiccation cracks, root casts, soil-ped casts, and tubes. Medial lake-bottom deposits are laminated siltstones, silty mudstones, or silty limestones that are dark gray to black with calcite laminae and grains and lenses, or streaks of pyrite; fossils are common, including fish scales and articulated fish, conchostracans, plants, spores, and pollen. Upper regressive lake margin, playa lake, and mudflat deposits are light- to dark-gray silty mudstone to argillitic siltstone or very fine grained sandstone, mostly thick bedded to massive, with desiccation cracks, intraformational breccias, faint wavy laminations, burrows, euhedral pyrite grains, and dolomite or calcite specks. Alkaline-lake cycles are similar to freshwater-lake cycles, but are thinner, averaging 3 m (10 ft), have fewer fossils (mainly conchostracans), and commonly have red beds, extensive desiccation features, and abundant analcime and dolomite specks in the upper parts of cycles. Thickness near Byram is about 1,070 m (3,510 ft). The formation thins to the southeast and northeast; thickness near Princeton is less than 700 m (2,297 ft).
Longwood Shale (Middle (?) and Upper Silurian)
Longwood Shale (Darton, 1894) - Dark-reddish-brown, thin- to very thick bedded shale interbedded with cross-bedded, very dark red, very thin to thin-bedded sandstone and siltstone. Lower contact conformable. About 100 m (330 ft) thick.
Lower Member of the Kirkwood Formation (lower Miocene, Aquitanian)
Lower Member - Complex unit in which facies changes are common. In outcrop, some of the lower member is a light-colored quartz sand (Grenloch facies of Isphording, 1970). The facies pinches out rapidly in the subsurface, and the unit is primarily a massive to finely laminated, dark-gray clay (Alloway clay of Kummel and Knapp, 1904). This clay facies occurs as far south as Clayton, Gloucester County, where the lower part changes to a fossiliferous clayey silt. The lower clayey facies thickens to over 30 m (98 ft) in the coastal region. Here, the lower facies is mostly dark-gray clayey silt that is locally very fossiliferous. The unit varies in thickness but is thickest, as much as 80 m (262 ft), in the southeastern part of the central sheet. South of Bridgeton, Cumberland County, sand is present at the top of the member. This sand thickens to over 23 m (75 ft) at the coast where it is part of the "800 foot" sand, the principal aquifer in the coastal region. Quartz and siliceous rock fragments are the major sand minerals. Feldspars typically constitute less than 10 percent of the sand fraction except in the reworked beds where they make up as much as 25 percent of the sand. Mica and wood fragments are minor constituents. The basal contact with the underlying unit is sharp and unconformable. Commonly there is a 0.3- to 1-m (1- to 3-ft)-thick zone along this contact in which coarse-grained quartz sand and some gravel are present. Because of the quartz sand in the lower member in outcrop, some considered the lower member and the Cohansey Formation to be transitional (Isphording, 1970). Obviously this is not the case as there are three other members (Shiloh Marl, Wildwood, and Belleplain) lying between the lower member and the Cohansey. The age of the lower member was determined from planktic foraminifera and diatoms, and from strontium-isotope age estimates. The foraminiferal assemblage includes Globigerina praebulloides, Globigerinoides trilobus, G. altiapertura, and Globorotalia siakensis. These species are characteristic of the lower Miocene Zone 5 of Blow (1969) of Burdigalian age. The diatom assemblage is characterized by Actinoptychus heliopelta, Aulacodiscus rogersii, Coscinodiscus lewisianus, Sceptroneis caduceus, and Triceratium acutum. These diatoms are characteristic of ECDZ 1 of Andrews (1988), which is considered to be early Miocene (Burdigalian) in age. The strontium-isotope analyses of shells from this member indicate ages from 23 to 20.2 Ma (Aquitanian), thereby extending the age of this member (Sugarman and others, 1993). The pollen in the clay facies of the Kirkwood, as determined from the ACGS-4 drillhole, are oak, hickory, and pine with smaller amounts of beech, black gum, sweet gum, alder, elm, linden, and birch. The sandy facies has essentially the same assemblage but has unusually high concentrations of beech. Exotic species such as Podocarpus and Momipites are common in the unit. The cool floral elements found in the overlying Belleplain and Wildwood Members were not found in the lower member.
Magothy Formation (Upper Cretaceous, middle and lower Santonian)
Magothy Formation - Sand, fine- to coarsegrained, locally very gravelly (pebbles less than 1.3 cm (0.5 in) in diameter) especially in updip areas, typically cross stratified, massive, horizontally bedded, light-gray to white, carbonized wood (several centimeters long) and colorless mica scattered throughout. Black to dark-gray, very carbonaceous clay is locally interstratified with the sand. No calcareous fossils were recovered from the Magothy Formation in the shallow subsurface. In the Freehold drillhole the thin basal bed of the Magothy is composed of quartz gravel (maximum clast diameter, about 2.5 cm (1 in)). The lower part of the formation above the gravel consists of thin-bedded white clay interbedded with fine- to coarse-grained, poorly sorted, thickbedded, light-colored, somewhat micaceous quartz sand. The interbedded clay becomes dark gray up section and the sand is slightly glauconitic and locally shelly. Quartz is the major sand mineral. Siliceous rock fragments, mica, and feldspar are minor constituents. In general, this formation appears to be fluvial near the base (upper delta plain) and gradually becomes more marine upward (shelf). The overall sedimentologic pattern suggests a net transgression during deposition of the Magothy with shelf deposits overriding a nonmarine (probably deltaic) facies. Downdip at Buena, Atlantic County, the Magothy is 22 m (72 ft) thick and is primarily a massive to finely laminated, dark-gray, woody clay-silt. Unit is as much as 55 m (180 ft) thick in the northern part of the central sheet and generally thins to the southwest. The age of the Magothy is best defined by pollen. Christopher (1979) placed this palynoflora in his Zone V of early and late Santonian age. He also recognized three assemblage zones within Zone V, the Complexiopollis exiqua-Santalacites minor Zone (lowest), the ?Pseudoplicapollis longiannulata-Plicapollis incisa Zone (middle), and the ?Pseudoplicapollis cuneata-Semioculopollis verrucosa Zone (highest). All three zones are present in the Magothy in New Jersey. The foraminifera Marginotruncana marginata and Rosita fornicata were collected from the Island Beach corehole at 550 m (1804 ft) and are indicative of the Dicarinella asymmetrica Zone. Because of the overall character of the foram assemblage it is probable that these fossils indicate a late Santonian rather than early Campanian age (H.J. Dowsett, written commun., 1992). The Magothy, therefore, is Santonian or older in age.
Magothy Formation (Upper Cretaceous, middle and lower Santonian)
Magothy Formation - Sand, quartz, fine- to coarse-grained, locally gravelly (especially at the base), white; weathers yellow brown or orange brown, interbedded with thin-bedded clay or dark-gray clay-silt mainly at the top of the formation. Muscovite and feldspar are minor sand constituents. Large wood fragments occur in many clay layers. Clay weathers to gray brown or white. Formation characterized by local vertical and lateral facies changes. The Magothy is best exposed and thickest (about 80 m (262 ft)) in the Raritan Bay area. The outcrop belt is widest in the north and narrows to the southwest. The formation is about 25 m (82 ft) thick or less in the southern sheet. The formation is poorly exposed because of its sandy nature and its widespread cover by younger sediments. The old geologic map of New Jersey (Lewis and Kummel, 1910-1912, revised 1950) showed the Magothy to consist of only one lithology (Cliffwood beds at Cliffwood Beach, Monmouth County). Subsequent pollen studies of the Magothy and the underlying Raritan Formation showed most of the Raritan to be the same age as the Magothy. Wolfe and Pakiser (1971) redefined and considerably expanded the Magothy. Kummel and Knapp (1904) had already recognized that the Magothy, as used here, contained a large number of lithologies. At the time of their study, the Magothy was extensively mined for clay and sand and was well exposed. Their subdivisions had economic designations (for example, Amboy stoneware clay). Barksdale and others (1943) later gave geographic names to these subdivisions, discussed individually below. The lower contact of the Magothy in the Delaware River valley is difficult to place because the lower part of the Magothy is lithically similar to the underlying Potomac Formation. The contact is placed at the base of the lowest dark-gray clay in the Magothy. The best faunas from the Magothy were obtained from siderite concretions and slabs in and near Cliffwood Beach representing only the top of the formation. These faunas were discussed in detail by Weller (1904, 1907) and supplemented by Sohl (in Owens and others, 1977). The presence of Ostrea cretacea in the Cliffwood Beach fauna suggests that the upper part of the Magothy is late Santonian in age. Wolfe and Pakiser (1971) and Christopher (1979, 1982) discussed the microfloral assemblage in the Magothy. Christopher subdivided the Magothy into three zones: Complexipollis exigua-Santalacites minor (oldest), ?Pseudoplicapollis longiannulata-Plicapollis incisa (middle), and ?Pseudoplicapollis cuneata-Semioculopollis verrucosa (youngest). The oldest zone, originally considered to be as old as Turonian, was subsequently considered to be post-Coniacian Christopher, 1982). The middle and upper zones are also probably Santonian. Christopher (1979) followed the nomenclature for the subdivisions elaborated upon earlier. The Cliffwood and Morgan beds, and, presumably the upper thin-bedded sequence, would include the youngest pollen zone; the Amboy Stoneware Clay Member and perhaps the uppermost part of the Old Bridge Sand Member, the middle pollen zone; and the lower part of the Old Bridge Sand Member and South Amboy Fire Clay Member, the oldest pollen zone. The Magothy is considered herein to be of Santonian age. Cliffwood beds - Typically very sandy, horizontally bedded to crossbedded, mainly small-scale trough crossbeds. Thin layers of dark, fine, carbonaceous matter are interbedded with sand. Carbonaceous units are conspicuously micaceous; the sand is less so. Sand is typically fine to medium grained and locally burrowed. Burrows include the small-diameter Ophiomorpha nodosa and some that are not clay lined. Slabs of dark-reddish-brown siderite were common at the base of the bluff at Cliffwood Beach before the outcrop was covered. Some of these slabs had many fossil molds, typically a large number of pelecypods. Lower in the section, between high and low tide level, there is a pale-gray clay-silt about 1.5 m (5 ft) thick with many small reddish-brown siderite concretions. These concretions have many fossils that were described in detail by Weller (1904). The Cliffwood beds are about 7.5 m (25 ft) thick in outcrop. Equivalents of the Cliffwood beds are exposed near the Delaware River between Trenton and Florence, Burlington County. These beds are mainly sand, as are those at Cliffwood Beach, but they tend to have more crossbedding than the typical Cliffwood strata and no burrows or marine fossils. In addition, beds of quartz gravel are present in the Cliffwood near Riverside, Burlington County. Morgan beds - Occur only in the northern part of the central sheet. They consist of interbedded, thin, dark-colored clay and fine-grained, light-colored, micaceous sand. Clay is locally more abundant in the Morgan than in the Cliffwood beds. Sand ranges from massive to locally crossbedded and locally has fine organic matter. This unit is exposed only in the South Amboy quadrangle where it is as much as 12 m (39 ft) thick. It grades downward into underlying clay. Amboy Stoneware Clay Member - Crops out only in the South Amboy quadrangle in the central sheet and is mainly dark-gray, white-weathering, interbedded clay and silt to fine-grained quartz sand. Clay has abundant, fine, carbonaceous matter and fine mica flakes. Small cylindrical burrows are abundant in this unit. Locally, the clay is interbedded with sand and contains large pieces of lignitized, bored (Teredolites) logs. Large slabs of pyrite-cemented sand are associated with the woody beds. Amber occurs in some of the wood. Unit is approximately 7.5 m (25 ft) thick, but pinches out along strike. The Amboy Stoneware is disconformable on the underlying sand. Old Bridge Sand Member - Predominantly a light-colored sand, extensively crossbedded and locally interbedded with dark-gray laminae; clay is highly carbonaceous, woody, in discontinuous beds, especially near the base. The scale of crossbedding varies from small to large. Locally, small burrows are present. Unit is as much as 12 m (39 ft) thick and rests disconformably on the underlying unit. South Amboy Fire Clay Member - Basal member of the Magothy Formation. Unit resembles the Amboy Stoneware Clay Member, particularly in its lensing character. Unit is best exposed in the central sheet in the South Amboy quadrangle and in the Delaware River valley at the base of the bluffs at Florence. The South Amboy is a dark, massive to finely laminated clay, locally oxidized to white or red. Unit fills large channels and has local concentrations of large, pyrite-encrusted, lignitized logs. Some of the clay is slumped, suggesting post-depositional undercutting during channel migration. The clay is interbedded with fine- to medium-grained, crossbedded sand. The basal contact with the underlying Raritan is well exposed in the Sayre and Fisher Pit in Sayreville, Middlesex County, where the contact is marked by a deeply weathered gravel zone.
Manasquan Formation (lower Eocene, Ypresian)
Manasquan Formation - Clay to clay-silt, massive to finely laminated, green to gray-green, extensively bioturbated. Calcareous microfossils are abundant in this unit. In the northwestern outcrop belt and shallow subsurface of the central sheet, the lower beds of the Manasquan Formation consist of a maximum of 10 m (33 ft) of fine- to coarse-grained, somewhat clayey, bluish-green glauconitic quartz sand. No calcareous macrofossils were found in this lithology. The sand minerals in the basal sand facies, excluding glauconite, consist of quartz, feldspar (10 to 25 percent), and siliceous rock fragments (a few percent). The glauconitic quartz sand is overlain to the southwest by a light- to dark-green, locally glauconitic, sandy clay-silt. This clay-silt is present at the base of the unit in the shallow subsurface. Eastward and in the intermediate subsurface, the Manasquan is primarily a clayey glauconite sand. In the deep subsurface, the Manasquan is primarily a massive to finely laminated, lightyellow clay-silt that has high concentrations of calcareous microfossils and has several hard indurated layers. In general, the formation thickens to the southeast where it is more than 60 m (197 ft) thick. The basal contact with the underlying Vincentown Formation is sharp and contains a thin zone, typically 0.61 m (2 ft) thick, of reworked glauconite sand, phosphatic debris, and sparse quartz granules. Gamma-ray logs through the Manasquan Formation have a large gamma spike along the basal contact. The age of the Manasquan was determined from calcareous nannofossils and, to a lesser degree, from foraminifera. The lower part of the Manasquan is assigned to the upper part of Zone NP 9 on the basis of the calcareous nannofossils Campylosphaera dela and Lophodolithus nascens and the absence of Zone NP 10 species. The upper part of the formation lies within Zone NP 13. This zone is characterized by the absence of Rhomboaster orthostylus and the presence of Discoaster lodoensis (Poore and Bybell, 1988). The foraminifera Planorotalites palmerae, which is present in this unit, has a range that correlates with the lower part of Zone NP 13 (Poore and Bybell, 1988).
Manhattan Schist (Lower Cambrian and (or) Late Proterozoic)
Manhattan Schist (Hall, in press) - Medium-dark gray, medium- to coarse-grained schist and gneiss composed of biotite, muscovite, quartz, and plagioclase, and local accessory minerals sillimanite, kyanite, tourmaline, and garnet. Contains some interlayered amphibolite. Unit is not exposed in the map area, but is present in boring logs.
Marcellus Shale (Middle Devonian)
Marcellus Shale (Vanuxem, 1840) - Medium-gray weathering, dark-gray to grayish-black, thin- to thick-bedded, fossiliferous, fissile and limonite-stained locally arenaceous shale. Lower contact grades downward over 12 m (40 ft) from black shale through limy shale, into silty limestone of the Buttermilk Falls Limestone (documented in drill core data of Fletcher and Woodrow, 1970). Approximately 274 m (900 ft) thick.
Marshalltown Formation (Upper Cretaceous, upper and middle Campanian)
Marshalltown Formation - Sand, quartz and glauconite, fine- to medium-grained, silty and clayey, massive, dark-gray; weathers light brown or pale red, extensively bioturbated. Very glauconitic in basal few meters; glauconite concentration decreases upward so that in upper part of unit, quartz and glauconite are nearly equal. Feldspar, mica, pyrite, and phosphatic fragments are minor sand constituents. Locally, very micaceous (mostly green chlorite) with sparse carbonized wood fragments. Fine-grained pyrite abundant throughout formation. Local thin, pebbly zones with large fossil impressions occur in the middle of the formation. In the upper part of the formation, quartz increases to about 40 percent. Unit crops out in a narrow belt throughout the map area and forms isolated outliers in the central sheet. Best exposures are along Crosswicks Creek in the Allentown quadrangle. In the southern sheet, the Marshalltown underlies a narrow belt in the uplands and broadens to the southwest. Many Marshalltown exposures occur along Oldmans Creek and its tributaries near Auburn, Gloucester County. The contact with the underlying Englishtown Formation is sharp and unconformable. The basal few centimeters of the Marshalltown contain siderite concentrations, clay balls, and wood fragments reworked from the underlying Englishtown. Many burrows, some filled with glauconite, project downward into the Englishtown for about one meter (3 ft) giving a spotted appearance to the upper part of the Englishtown (Owens and others, 1970). The Marshalltown is the basal transgressive unit of a sedimentation cycle that includes the regressive deposits of the overlying Wenonah and Mount Laurel Formations resembling the overlying Red Bank Formation to Navesink Formation cycle in its asymmetry. Within the map area, only a few long-ranging megafossils occur in the Moorestown quadrangle (Richards, 1967). To the south, in the type area, Weller (1907) reported diverse molluskan assemblages indicating a Campanian age. More importantly, Olsson (1964) reported the late Campanian foraminifera Globotruncana calcarata Cushman from the upper part of the formation. No G. calcarata were found during our investigations. Wolfe (1976) assigned the pollen assemblage of the Marshalltown to the CA5A Zone considered to be Campanian. The Marshalltown has most recently been assigned to Zone CC 20-21 (Sugarman and others, 1995) of middle and late Campanian age (Perch-Nielsen, 1985).
Martinsburg Formation, undivided (Upper and Middle Ordovician)
Martinsburg Formation, undivided (Bayley and others, 1914) - Interbedded light-olive-gray, greenish-gray-, or dark-yellowish-brown- weathering, medium-dark- to dark-gray, laminated to medium-bedded graywacke and siltstone and olive-gray- to dark-yellowish-brown-weathering, medium-dark- to dark-gray slate. Turbidite cycles are common. Mapped only east of Lafayette and west of Lake Grinnell where thickness is at least 305 m (1000 ft).
Merchantville Formation (Upper Cretaceous, lower Campanian)
Merchantville Formation - Sand, glauconite, locally has high quartz content, very clayey and silty, massive to thick-bedded, grayish-olive-green to dark-greenish-gray; weathers moderate brown or moderate yellow brown. Mica, feldspar, and pyrite are minor sand constituents. Very micaceous at base. Locally, has extensive iron incrustations in near-surface weathered beds. Fossil molds are mostly phosphatic. Fossils typically occur in siderite concretions. No calcareous fossils were found in outcrop. The Merchantville forms a continuous narrow to wide belt throughout the map area. The unit is about 6 m (20 ft) thick in the northern part of the central sheet, about 20 m (66 ft) thick in the Trenton area, and 12 to 15 m (39-49 ft) thick throughout the southern sheet. The formation is best exposed in the Trenton East quadrangle, mainly in the tributaries on the western side of Blacks Creek and south of Bordentown, Burlington County, where the entire thickness of the formation can be seen in gullies (Owens and Minard, 1964b). The basal contact with the underlying Magothy or Cheesequake Formations is sharp and disconformable. At most places, a reworked zone about 0.3 to 1 m (1-3 ft) thick is present at the base. This basal bed contains reworked lignitized wood, siderite concretions as much as 13 cm (5 in) in diameter, scattered pebbles and coarse-grained quartz sand and is burrowed. Most burrows project downward into the underlying formations. The Merchantville is the basal bed of a lower Campanian transgressive-regressive cycle that includes the overlying Woodbury and Englishtown Formations. Merchantville faunas were analyzed by Sohl (in Owens and others, 1977) who concluded that northern fauna represented deposition on a lower shoreface or in the transition to an inner shelf, whereas the southern fauna was a deeper water assemblage, probably inner shelf. Macrofossils occur as internal and external molds and include the ammonites Menabites (Delawarella) delawarensis and Scaphites (Scaphites) hippocrepis III. The Scaphites is of the type III variety of Cobban (1969) and is indicative of the lower, but not the lowest, Campanian. More recently, Kennedy and Cobban (1993), detailing the ammonite assemblage that includes Baculites haresi, Chesapeakella nodatum, Cryptotexanites paedomorphicus sp., Glyptoxoceras sp., Menabites (Delawarella) delawarensis, M. (Delawarella) vanuxemi, Menabites (Bererella) sp., Pachydiscus (Pachydiscus) sp., Placenticeras placenta, Pseudoscholenbachia cf. P. chispaensis, Scaphites (Scaphites) hippocrepis III, Submortoniceras punctatum, S. uddeni, and Texanites (Texanites) sp., concluded that the Merchantville is of late early Campanian age. Wolfe (1976) indicated that the Merchantville microflora was distinct from overlying and underlying units and designated it Zone CA2 of early Campanian age.
Metabasalt (Late Proterozoic)
Metabasalt - Sequence of conformably layered volcanic rocks of fine-grained to aphanitic, greenish-gray, retrogressively metamorphosed greenstone, greenschist, and basalt. Greenschist contains clots and lenses of blue quartz and abundant sulfide. Unit does not crop out and is known only from subsurface borings and artificial exposures. Interpreted to be Late Proterozoic by Volkert and Drake (1993) on the basis of geochemical similarity to Late Proterozoic metadiabase dikes in New Jersey Highlands.
Minisink Limestone and New Scotland Formation, undivided (Lower Devonian)
Minisink Limestone and New Scotland Formation, undivided - Minisink Limestone (Epstein and others, 1967) - Light-medium-gray-weathering, medium-gray, fine-grained, medium-bedded, partly massive, argillaceous fossiliferous limestone. Some nodules and lenses of purer limestone occur locally. Lower contact gradational. Thickness uniformly 7 m (23 ft). New Scotland Formation (Clarke and Schuchert, 1899) - Upper part is dark-gray, very fine grained, laminated to thin-bedded siliceous shale containing pods of medium-dark-gray, very fine grained limestone; scattered thin beds and lenses of medium-gray, fine-grained argillaceous fossiliferous limestone; and small dark-gray chert nodules. Lower part is medium-dark-gray, thin-bedded, siliceous, fossiliferous calcareous shale. Contains thin beds and lenses of medium-gray, fine-grained, highly fossiliferous, argillaceous limestone containing nodules, lenses and, locally, irregular beds of dark-gray chert. Lower contact abrupt and placed at top of calcareous quartz sandstone. Total thickness is approximately 23 m (75 ft).
Mt. Laurel Formation (Upper Cretaceous, upper Campanian)
Mt. Laurel Formation - Sand, quartz, massive to crudely bedded, typically coarsens upward, interbedded with thin clay beds. Glauconite and feldspar are minor sand constituents. Muscovite and biotite are abundant near the base. Lower part of formation is a fine- to medium-grained, clayey, dark-gray, glauconitic (maximum 25 percent) quartz sand. Typically weathers to white or light yellow and locally stained orange brown by iron oxides. Small pebbles scattered throughout, especially in the west-central area. Locally, has small, rounded siderite concretions in the interbedded clay-sand sequence. Granules and gravel are abundant in the upper 1.5 m (5 ft). Upper beds are light gray and weather light brown to reddish brown. The Mount Laurel is 10 m (33 ft) thick from the Roosevelt quadrangle to the Runnemede quadrangle in the central sheet. Thickness varies in the northern part of the map area due, in part, to extensive interfingering of this formation with the underlying Wenonah Formation. Weller (1907) and Kummel (1940) recognized only about 1.5 m (5 ft) of the Mount Laurel in the north. In this report those beds are assigned to the overlying Navesink Formation. The interbedded sequence, the major facies in the north, ranges to about 4.5 m (15 ft) thick. These interbeds have well-developed large burrows (Martino and Curran, 1990), mainly Ophiomorpha nodosa, and less commonly Rosselia socialis. The Mount Laurel is gradational into the underlying Wenonah Formation. A transition zone of 1.5 m (5 ft) is marked by an increase in clay, silt, and mica into the Wenonah, especially in the west-central area of the central sheet. The oyster Agerostrea falcata occurs in the lower part of the formation. Exogyra cancellata and Belemnitella americana are abundant in upper beds in the west-central area of the central sheet (New Egypt quadrangle). The Mount Laurel Formation is of late Campanian age based on the assignment of Zone CC 22b to the formation by Sugarman and others (1995) and the occurrence of Exogyra cancellata near Mullica Hill, Gloucester County.
Navesink Formation (Upper Cretaceous, Maastrichtian)
Navesink Formation - Sand, glauconite, medium-grained, clayey and silty, massive, dark-gray to dark-gray-green, extensively bioturbated, locally contains large calcareous shells; sand-size mica, locally abundant; weathers light brown or red brown. Basal quartz sand is fine- to coarse-grained, pebbly, massive, light-yellow, and somewhat glauconitic, as much as 2 m (7 ft) thick and formed by the reworking of the underlying Mount Laurel Formation (Owens and others, 1977). Exogyra costata and the belemnite Belemnitella americana occur in the basal quartz sand. Crops out in a narrow belt throughout map area. Fresh exposures occur along tributaries of Raccoon Creek near Mullica Hill, Gloucester County. The Navesink is 3 to 7.5 m (10-25 ft) thick. The Navesink and Red Bank deposits represent a transgressive (Navesink)-regressive (Red Bank) cycle of sedimentation (Owens and Sohl, 1969). The cycle is unconformity-bounded at top and bottom. Within the cycle, the formational contact is gradational. The age of the Navesink was determined from both the macrofauna and microfauna. Planktic foraminifera from the lower part of the Navesink are indicative of the Rugotruncana subcircumnodifera Subzone of early Maastrichtian age (Smith, in Owens and others, 1977). The upper part contains the mollusks Exogyra costata, Sphenodiscus lobatus, and Pycnodonte vesicularis indicating a middle to late Maastrichtian age. Planktic foraminifera from the upper part represent the Gansserina gansseri Subzone of middle Maastrichtian age (Smith, in Owens and others, 1977). Pollen in the Navesink and Sandy Hook Member of the Red Bank are similar; the Navesink microflora is a CA6/MA-1 Zone in Wolfe's (1976) classification. The Navesink, therefore, ranges from early to late Maastrichtian. Sugarman and others (1995) assigned a middle Maastrichtian Zone CC 25 to the Navesink.
Oriskany Group, undivided (Lower Devonian)
Oriskany Group, undivided (Willard, 1938) - Thickness ranges from 38 m (125 ft) in southwest to 52 m (170 ft) in northeast. Ridgely Sandstone (Swartz and others, 1913) - White-weathering, medium-gray, medium- to thick-bedded, carbonate-cemented quartz-pebble conglomerate and coarse quartz sandstone, which contain abundant brachiopods. Moderately well sorted, subrounded sand gains. Unit thins northeastward and pinches out at Peters Valley. Lower contact abrupt. Thickness ranges from 0 to 10 m (0-32 ft). Shriver Chert (Swartz and others, 1913) - Medium- to dark-gray-weathering, black to dark-gray, medium-to-thick-bedded siltstone and shale containing interbedded black chert and local chert-bearing limestone. Present only in southwestern part of outcrop area where lower contact is gradational with silty limestone of Glenarie Formation. Thickness ranges from 0 to 9 m (0-30 ft). Glenarie Formation (Chadwick, 1908) - Medium-gray-weathering, medium- to dark-gray, fine-grained, thin- to medium-bedded, fossiliferous, silty limestone, and local chert lenses. Unit thickens to northeast. Lower contact probably gradational. Thickness ranges from 17 to 52 m (55-170 ft).
Ouachitite breccia (Early Silurian? and Late Ordovician)
Ouachitite breccia - Medium-dark-gray, fine-grained ouachitite (olivine-free biotite lamprophyre) containing pebble- to cobble-size xenoliths of Middle Proterozoic rock, dolomite of the Kittatinny Supergroup(?), the Martinsburg Formation, and autoliths of potassic syenite, lamprophyre, and carbonatite. Found in numerous diatremes in the Beemerville area; largest of at Rutan Hill.
Passaic Formation (Lower Jurassic and Upper Triassic)
Passaic Formation - Predominantly red beds consisting of argillaceous siltstone; silty mudstone; argillaceous, very fine grained sandstone; and shale; mostly reddish-brown to brownish-purple, and grayish-red. Red beds occur typically in 3- to 7-m (10- to 23-ft-)-thick, cyclic playa-lake-mudflat sequences and fining-upward fluvial sequences. Lamination is commonly indistinct due to burrowing, desiccation, and paleosol formation. Where layering is preserved, most bedforms are wavy parallel lamination and trough and climbing-ripple cross lamination. Calcite- or dolomite-filled vugs and flattened cavities, mostly 0.5 to 0.2 mm (0.02-0.08 in) across, occur mostly in the lower half. Sand-filled burrows, 2 to 5 mm (0.08-0.2 in) in diameter, are prevalent in the upper two-thirds of the unit. Desiccation cracks, intraformational breccias, and curled silt laminae are abundant in the lower half. Lake cycles, mostly 2 to 5 m (7-16 ft) thick, have a basal, greenish-gray, argillaceous siltstone; a medial, dark-gray to black, pyritic, carbonaceous, fossiliferous, and, in places, calcareous lake-bottom fissile mudstone or siltstone; and an upper thick-bedded, gray to reddish and purplish-gray argillaceous siltstone with desiccation cracks, intraformational breccias, burrows, and mineralized vugs. Thickness of the formation between Sourland Mountain and Sand Brook syncline is about 3,500 m (11,483 ft).
Passaic Formation Conglomerate and Sandstone facies (Lower Jurassic and Upper Triassic)
Passaic Formation Conglomerate and Sandstone facies - Conglomeratic sandstone (JTrpsc) is brownish-red pebble conglomerate, medium- to coarse-grained, feldspathic sandstone and micaceous siltstone; unit is planar to low-angle trough cross laminated, burrowed, and contains local pebble layers. Unit forms upward-fining sequences 0.5 to 2.5 m (1.6-8 ft) thick. Conglomeratic sandstone thickness exceeds 800 m (2,625 ft).
Passaic Formation gray bed (Lower Jurassic and Upper Triassic)
Passaic Formation gray bed - Upper Triassic gray lake deposits (Trpg) consist of gray to black silty mudstone, gray and greenish- to purplish-gray argillaceous siltstone, black shale, and medium- to dark-gray, argillaceous, fine-grained sandstone and are abundant in the lower half of the Passaic Formation. Gray lakebeds occur in groups of two to five cycles although they also occur as single cycles in some parts of the formation. Several lakebed sequences consisting of one or two thick groups of drab-colored beds as much as 30 m (98 ft) thick or more can be traced over tens of kilometers. Many gray-bed sequences are locally correlated within fault blocks; some can be correlated across major faults or intrusive rock units. Thickness of the (entire Passaic) formation between Sourland Mountain and Sand Brook syncline is about 3,500 m (11,483 ft).
Passaic Formation gray bed (Lower Jurassic and Upper Triassic)
Passaic Formation gray bed - Rhythmic cycles 2 to 7 m (7-23 ft) of thick gray-bed sequences (Trpg), termed Van Houten cycles by Olsen (1985), contain basal thin-bedded to finely laminated shale to siltstone, which grade upward through laminated to micro-laminated, locally calcareous mudstone to siltstone and finally into massive silty mudstone. Lowest part of cycle has some desiccation features and local fossils; middle part has highest organic content and the most fossils; highest part contains mudcracks, burrows, and root casts. Gray-bed cycles are abundant in lower half of Passaic Formation and less common in upper half.
Passaic Formation Limestone-clast Conglomerate facies (Lower Jurassic and Upper Triassic)
Passaic Formation Limestone-clast Conglomerate facies - Limestone conglomerate unit (JTrpcl) is medium-bedded to massive, pebble to boulder conglomerate. Clasts are subangular dolomitic limestone in matrix of brownish- to purplish-red sandstone to mudstone; matrix weathers light-gray to white near faults. Maximum thickness unknown.
Passaic Formation Mudstone facies (Lower Jurassic and Upper Triassic)
Passaic Formation Mudstone facies - Sandy mudstone (JTrpms) is reddish-brown to brownish-red, massive, silty to sandy mudstone and siltstone, which are bioturbated, ripple cross-laminated and interbedded with lenticular sandstone. To southwest where similar lithologic units also occur, they have not been mapped separately, but have been included in undivided unit JTrp.
Potomac Formation (Upper Cretaceous, lower Cenomanian)
Potomac Formation - Predominantly clay to clay-silt, thinly laminated to thick-bedded, mottled red, white, and orange-brown, less commonly dark-gray and woody; interbedded with thin beds and lenses of very fine to medium-grained, massive, white to orange-brown, micaceous sand. Lithologies are typical of the shallow subsurface. Down dip, these lithologies interfinger with thin to thick beds of marine clay-silt, commonly glauconitic and locally shelly. Marine beds are most prevalent in the southernmost part of the southern sheet. Unit 3 was cored in its entirety at Freehold where it is approximately 75 m (246 ft) thick. In the core, the basal 6 m (20 ft) consists of red or mottled red and white clay interbedded with gravel and fine- to coarse-grained sand. The clay is pervaded by reddish-brown siderite. Most of the overlying beds consist of interbedded dark-colored clay, locally weathered to pale yellow or white, and fine- to medium-grained, light-colored sand. Layers that contain fine black carbonaceous material to large lignitized wood pieces are common in unit 3 in this core. At Toms River, the unit is about 60 m (197 ft) thick and consists of dark- to pale-gray clay, locally weathering to white or yellowish gray, and light-colored, micaceous sand. In general, the darker colored clay is more common in the upper part of the section. Locally, the sand has very small amounts of glauconite which may indicate some local marine influence during sedimentation. The age of unit 3 was determined from pollen in the nonmarine deposits and foraminifera in the marine sections. Typical forms found in Zone III in New Jersey are Ajatipollis sp. A, Tricolpites nemejci, T. vulgaris, Tricolporoidites bohemicus, Tricolporoidites sp. A, T. sp. B, and Tricolporopollenites sp. B (Doyle and Robbins, 1977). In the marine facies, Petters (1976) reports a planktic foraminiferal suite containing Praeglobotruncana delrioensis and Rotalipora greenhornensis. Both the pollen and foraminiferal assemblages suggest an early Cenomanian age.
Potomac Formation, unit 3 (Upper Cretaceous, lower Cenomanian)
Potomac Formation - Sand, fine- to coarse-grained, locally gravelly, crossbedded, light-colored, interbedded with white or variegated red and yellow, massive clay, and rarely dark-gray, woody clay. The Potomac Formation crops out only in the Delaware River valley where the river and its tributaries have eroded away the overlying formations. The Potomac has been mapped in a broad belt parallel to the inner edge of the Coastal Plain. Although mapped in a broad belt, the Potomac is very poorly exposed because of the widespread cover of surficial sediments. The best exposures occur where surficial material is mined away in the Camden area. Unit is about 45 m (148 ft) thick. Contact with the overlying Magothy Formation is difficult to pick where the basal Magothy also contains variegated clays. Most of the basal Magothy has more dark-colored clay, and the contact was drawn by using this criterion. The basal contact of the Potomac with the underlying crystalline rock is not exposed in New Jersey. Biostratigraphically, the Potomac has been separated into pollen zones I, II, and III (Doyle, 1969; Doyle and Robbins, 1977). Samples from the Potomac Formation in the Camden area and along the Delaware River nearby contain pollen assemblages of early Cenomanian age (Zone III) (Les Sirkin, written commun., 1988).
Pyroxene Gneiss (Middle Proterozoic)
Pyroxene Gneiss - White- to tan-weathering, greenish-gray, fine- to medium-grained, well-layered gneiss containing oligoclase, clinopyroxene, variable amounts of quartz, and trace amounts of opaque minerals and titanite. Some phases contain scapolite and calcite. Commonly interlayered with pyroxene amphibolite or marble.
Pyroxene Granite (Middle Proterozoic)
Pyroxene Granite - Gray- to buff- or white-weathering, greenish-gray, medium- to coarse-grained, massive, gneissoid to indistinctly foliated granite containing mesoperthite to microantiperthite, quartz, oligoclase, and clinopyroxene. Common accessory minerals include titanite, magnetite, apatite, and trace amounts of pyrite. Some phases are monzonite, quartz monzodiorite, or granodiorite. Locally includes small bodies of amphibolite not shown on map.
Quartz-Oligoclase Gneiss (Middle Proterozoic)
Quartz-Oligoclase Gneiss - White-weathering, light-greenish-gray, medium- to coarse-grained, moderately layered to indistinctly foliated gneiss and lesser amounts of granofels composed of quartz, oligoclase or andesine, and, locally, biotite, hornblende and (or) clinopyroxene. Contains thin amphibolite layers.
Ramseyburg Member (Upper and Middle Ordovician)
Ramseyburg Member (Drake and Epstein, 1967) - Interbedded medium- to dark-gray, to brownish-gray, fine- to medium-grained, thin- to thick-bedded graywacke sandstone and siltstone and medium- to dark-gray, laminated to thin-bedded shale and slate. Unit may form complete turbidite sequences, Tabcde (Bouma, 1962), but basal cutout sequences Tcde dominate. Basal scour, sole marks, and soft-sediment distortion of beds are common in graywacke. Thermally metamorphosed near intrusive bodies. Lower contact placed at bottom of lowest thick- to very thick bedded graywacke, but contact locally grades through sequence of dominantly thin-bedded shale and slate and minor thin- to medium-bedded discontinuous and lenticular graywacke beds in the Bushkill member. Parris and Cruikshank (1992) correlate unit with Orthograptus ruedemanni to lowest part of Climacograptus spiniferus zones of Riva (1969, 1974). Thickness ranges from 640 m (2,100 ft) in Delaware River Valley, to 1,524 m (5,000 ft) near Stillwater, to 1067 m (3,500 ft) at New York State line.
Raritan Formation (Upper Cretaceous)
Raritan Formation (Cook, 1868) - Consists of upper clayey-silt (Woodbridge Clay Member) and lower sand (Farrington Sand Member) in map area. Woodbridge Clay Member is palered-orange weathering, grayish-black to dark-gray micaceous silt, very clayey; interbedded and locally interbedded with light-gray, very clayey, fine- to very-fine-grained micaceous sand containing primarily quartz and feldspar. Abundant layers of small, pyrite-coated wood fragments. Siderite in discontinuous beds and in flattened slab concretions as much as 1 m (3 ft) in diameter are common. Mollusk casts common in siderite near top of formation. Typically about 24 m (80 ft) thick. Farrington Sand Member is white, fine-to medium-grained, very micaceous, crossbedded sand, interbedded with thin to thick, darkgray, silty beds. Exposed only in pits dug below the overlying Woodbridge Clay Member. Typically about 8 m (25 ft) thick. Fossils include late Cenomanian ammonites Metoicoceras bergquisti and Metengonoceras sp. in upper part of Woodbridge (Cobban and Kennedy, 1990) and pollen of the Complexipollis-Atlantopollis assemblage zone (= Zone IV) of late Cenomanian to early Turonian age (Christopher, 1979; 1982).
Raritan Formation (Upper Cretaceous, upper Cenomanian)
Raritan Formation - Clay, silty, massive, dark-gray, shelly. Unit is generally restricted to the deep subsurface and only subcrops in the northern part of the central sheet. Petters (1976) proposed a new formation, the Bass River Formation, which included the Raritan as well as the lowermost part of the Magothy and the uppermost part of the Potomac Formation, unit 3. In this report, the name Bass River is not used. Thickness values were obtained from interpretations of geophysical logs from the few drillholes that penetrated this formation; consequently, these values are, at best, speculative. It is estimated that the Raritan is at most 100 m (328 ft) thick in the southernmost part of New Jersey. The formation contains both nonmarine and marine facies. The Freehold drillhole shows the best section containing both facies. In this drillhole the Raritan is approximately 60 m (197 ft) thick. The lower 12 m (39 ft) consists of interbedded, fine- to medium-grained, thin- to thick-bedded, light to dark-colored quartz sand and light- to dark-colored clay or clayey silt. Small to large pieces of lignitized wood are characteristic of and common to abundant in these beds. The middle 30 m (98 ft) consists of laminated to thinly bedded, dark-gray, micaceous clay and fine-grained, light-colored, micaceous quartz sand. Reddish-brown secondary cementation is common in the strata of this interval. Lignitized wood fragments are also locally abundant in these beds but on average the wood pieces are much smaller than those seen in the basal beds. The upper 18 m (59 ft) also is dominated by the laminated to thin-bedded sequences of micaceous clay and quartz sand but has small amounts of glauconite sand. A thin layer of large fossils (primarily Exogyra woolmani) is present in these upper beds. At the very top of this interval some of the beds are cemented by siderite. In general, the Raritan appears to be fluvial in the lower part, marginal marine in the middle, and marine at the top. North and west of the Freehold drillhole the Raritan is mostly interbedded nonmarine crossbedded sand and black to variegated clay. At Island Beach, southwest of Freehold, the Raritan is wholly marine and consists largely of dark-gray, shelly, micaceous clay at the base and fine-grained, dark-gray, shelly, micaceous clay at the top. It is assumed that the Raritan is late Cenomanian to possibly early Turonian in age as determined from northern New Jersey sections. In outcrop, the Raritan is early late Cenomanian in age on the basis of ammonites (Cobban and Kennedy, 1990). Pollen from these outcrops belongs to the Complexiopollis-Atlantopollis Assemblage Zone (zone IV, Christopher, 1979). Downdip, Petters (1976) reports the planktic foraminifer Marginotruncana helvetica, a middle Turonian marker, from beds assigned to pollen zone IV at Toms River, Ocean County.
Raritan Formation (Upper Cretaceous, upper Cenomanian)
Raritan Formation - Consists of an upper clayey silt (Woodbridge Clay Member) and a lower sand (Farrington Sand Member). Formation occurs only in northern part of central sheet. Woodbridge Clay Member - Silt, clayey, dark-gray; weathers to red brown or white, locally interbedded with light-gray, clayey, fine- to very fine grained sand (primarily quartz and mica with little feldspar). Very micaceous (muscovite, chlorite, and biotite) in both silty and sandy beds. Very woody, mostly fine pieces in layers and coated with pyrite. Locally, tree stumps, in upright position, are found near base of unit as are transported individual logs several feet in length. Siderite occurs in discontinuous beds and as flattened slab concretions as much as 0.6 m (2 ft) in maximum diameter. Fossil casts of marine mollusks are present, particularly near the top of the formation. Locally, well-developed burrows of Ophiomorpha nodosa filled with iron oxides weather out of the clay-silt. The Woodbridge is approximately 20 m (66 ft) thick in the vicinity of Sayreville, Middlesex County, where the South River has stripped away the overlying Magothy Formation, and it crops out in many places in the Perth Amboy and New Brunswick quadrangles to the north, but not in the quadrangles to the south or southwest. The Woodbridge does not crop out in the Delaware River valley southwest of Trenton. The late Cenomanian ammonites Metoicoceras bergquisti and Metengonoceras sp. were described from the upper part of the Woodbridge (Cobban and Kennedy, 1990). Pollen from the unit belongs to the Complexipollis-Atlantopollis Assemblage Zone of latest Cenomanian and early Turonian age (Christopher, 1979, 1982). Farrington Sand Member - Sand, quartz, fine- to medium-grained, crossbedded, very micaceous, white, interbedded with thin to thick, dark, silt beds. Rock fragments are a minor sand constituent. No burrows were observed in the unit. Unit is exposed only in pits dug below the overlying Woodbridge Clay Member. Typically, thickness is about 9 to 10.5 m (30-34 ft). Pollen from the Farrington is similar to the pollen in the Woodbridge.
Rondout and Decker Formations, undivided (Lower Devonian and Upper Silurian)
Rondout and Decker Formations, undivided - Rondout Formation (Clarke and Schuchert, 1899) - Upper part is medium-gray weathering, medium-dark-gray, very fine to fine-grained, medium-bedded, fossiliferous, argillaceous limestone. Middle part is light-medium-gray-weathering, medium-gray, laminated to medium-bedded, argillaceous dolomite. Locally contains deep desiccation polygons. Lower part is medium-gray-weathering, medium- to dark-gray, very fine to medium-grained, medium-bedded fossiliferous limestone. Silurian-Devonian boundary placed in middle of formation (Denkler and Harris, 1988). Lower contact abrupt and placed at top of highest calcareous quartz sandstone. Thickness approximately 12 m (40 ft). Decker Formation (White, 1882) - Light-gray- to yellowish-gray-weathering, light- to medium-gray, calcareous quartz siltstone, sandstone, and fine-pebble conglomerate locally interbedded with fossiliferous medium-gray, medium- to coarse-grained limestone and very fine grained, thin- to medium-bedded dolomite. Lower contact gradational. Thickness varies from 15 m (50 ft) near Duttonville to 25 m (82 ft) at Wallpack Center.
Schoharie Formation (Lower Devonian)
Schoharie Formation (Vanuxem, 1840) - Yellowish-gray- to locally pale-olive-weathering, medium- to dark-gray, medium- to thick-bedded, calcaeous siltstone and lesser amounts of silty limestone. Locally contains thin ribs or pods of black chert in limestone. Limestone content decreases in lower part of unit. Contains the trace fossil Taonurus, a grazing trail. Lower contact gradational and placed at top of highest massive siltstone below lowest limestone. Thickness approximately 53 m (175 ft).
Shark River Formation (upper and middle Eocene, Priabonian through Lutetian)
Shark River Formation - Consists of three lithofacies, a basal clayey, greenish-gray glauconite sand; a middle dark-green to gray-green silty clay or clayey silt; and an upper medium-gray to gray-green, silty quartz sand. Updip beds are cyclic with a fine- to medium-grained, somewhat clayey, fossiliferous, dark-green, glauconite-quartz (25 percent) sand at the base. The basal lithofacies is about 12 m (39 ft) thick in the southern sheet and 3 m (10 ft) thick in the central sheet. There is a general increase in quartz sand upward and a change in color to dark gray or brownish gray. Locally, some of the beds are more clayey and have more calcareous shell fragments. The middle clay and silt facies is typically the thickest lithofacies in most Shark River sections (as much as 38 m (125 ft) thick) and is massive to thick bedded. The thick-bedded parts typically consist of intercalated silty and clayey beds that are extensively bioturbated. Macro- and microfossils are abundant in this facies. Most of the macrofossils are thin-walled pelecypods. This facies is gradational into the upper quartz-sand facies. The quartz sand is well developed in the Toms River Chemical Plant drillhole, Toms River, Ocean County (sheet 1). This facies apparently was beveled off in the updip areas during erosion prior to deposition of the Kirkwood Formation. The Shark River Formation in the updip area near Bridgeton, Cumberland County (sheet 2), is about 52 m (171 ft) thick. All of the Shark River lithologies in the downdip area are extensively bioturbated. The Shark River is thickest (more than 60 m (197 ft)) in a trough that lies near the middle of the southern sheet. The contact between the Shark River and the underlying Manasquan Formation is sharp and contains a thin zone of reworked glauconite sand, granules of quartz, and phosphatic debris. On most gamma-ray logs through this contact, there is a sharp gamma high reflecting the concentration of phosphatic sediment. The vertical arrangement of facies in this formation is from a transgressive (mostly clay) facies at the base to a regressive (mostly sand) facies at the top. Calcareous nannofossils and foraminifera were used to date this unit. Where the unit is thickest, the nannofossils range from the upper part of Zone NP 14 (Rhabdosphaera inflata) to the lower part of Zone NP 18 (Chiasmolithus oamaruensis). The entire sequence of Zones NP 14 through NP 18 was observed only in the ACGS-4 corehole near Mays Landing. The planktic foraminifera zones range from the Turborotalia frontosa Zone at the base to the Turborotalia pomeroli/Turborotalia cerroazulensis Zone at the top. A middle to early late Eocene age for the Shark River is indicated by these zones (Poore and Bybell, 1988).
Shark River Formation (upper and middle Eocene, Priabonian through Lutetian)
Shark River Formation - Glauconite sand, silt, and clay, medium- to coarse-grained, light-brown to medium-gray, locally indurated at top and noncalcareous throughout. Mollusk impressions (mainly Venericardia perantiqua) were observed in the Farmingdale quadrangle. The Shark River is exposed only at a few localities in the central sheet near Farmingdale, Monmouth County, along the Manasquan and Shark Rivers and in several tributaries to Deal Lake near Asbury Park in the Asbury Park quadrangle (Sugarman and Owens, 1994). Most outcrops are small, less than 3 m (10 ft) in height. The contact with the underlying Manasquan Formation was not observed. The Shark River is about 18 m (59 ft) thick and consists of two fining-upward cycles: a glauconite sand is present at the base and a clay or silt is present at the top of each cycle. Calcareous nannofossils in subsurface Shark River sections indicate Zones NP 14 through NP 18 (Martini, 1971) (middle Eocene and early late Eocene).
Shawangunk Formation (Middle and Lower Silurian)
Shawangunk Formation (Mather, 1840; Epstein and Epstein, 1972) - Upper part is medium- to medium-dark-gray, or dark-greenish-gray, medium- to thick-bedded sandstone and pebble conglomerate having well rounded grains, some of which are limonite stained. Conglomerate consists of matrix-supported quartz and subordinate shale pebbles as long as 5 cm (2 in.) in poorly to well-sorted, planar tabular to trough crossbedded sandstone. Local black to dark-greenish-gray, thin-bedded shale near upper contact. Middle part, occurring in southwest and sporadically in northeast, is light- to medium-dark-gray, greenish-gray, interbedded thin- to medium-bedded, planar tabular to trough cross-bedded shale and sandstone. Grains are well rounded and moderately to well sorted. Contains sparse graphite flakes. Lower part is light- to medium-gray to light-olive-gray, thin- to thick-bedded quartz and feldspathic sandstone, quartzite, and quartz-pebble conglomerate, which is matrix-supported, poorly to well sorted, cross to planar bedded. Clasts are primarily quartz and sparse dark-gray argillite and black chert. Sandstone is feldspathic and locally approaches an arkose in compostion. Lower contact unconformable and, at places, is a fault of small displacement. Thickness approximately 427 m (1,400 ft).
Shiloh Marl Member of the Kirkwood Formation (lower Miocene, Burdigalian)
Shiloh Marl Member - Consists of (1) a lower laminated, micaceous, locally fossiliferous (typically thin-walled, small mollusks), dark-gray clay interbedded with very fine grained sand and (2) an upper medium- to coarse-grained, gravelly, massive, pale-brown to medium-gray sand with scattered thin-walled mollusks. Thin, dark-gray clay layers interbedded with thin layers of lignite are common in this upper interval. Like the Wildwood, this unit occurs mainly within the southern sheet and the southeastern part of the central sheet. Thicknesses vary within the basin but are a maximum of 55 m (180 ft). In the Island Beach corehole the unit is clayey at the base and sandy at the top. The basal contact with the underlying unit is sharp but there is little reworked debris along this contact. In detail, the lowest 4.5 m (15 ft) of the unit is a fine- to medium-grained, massive, micaceous, extensively bioturbated, somewhat clayey, quartz sand. Small wood fragments are common. This basal sand bed grades upward into a sequence of horizontally bedded, light- to dark-gray clay and very fine grained, somewhat micaceous quartz sand. Color banding in this interval is strong. A very coarse grained, pale-gray quartz sand with some granules is interbedded with this dominantly clayey sequence. The clayey sequence is overlain by a medium-grained, massive, bioturbated, medium-gray sand similar to the basal sand. This sand grades into a thin- to thick-bedded and crossbedded sequence of dark-gray and brown sand that increases in grain size from coarse to very coarse grained up section. Most of the sand is quartz with lesser amounts of potassium feldspar (6 to 16 percent of the sand fraction). Near the top of the unit, quartz gravel is a common constituent in the very coarse grained sand bed. The age of the Shiloh is early Miocene (Burdigalian) as determined from diatoms. The Shiloh contains Actinoptychus heliopelta (ECDZ 1 of Andrews, 1987, 1988). Strontium age determinations on shells from this unit yielded ages of 20.9 to 19.7 Ma confirming the early Burdigalian age. Pollen studies indicate that the Shiloh has unusually high concentrations of Fagus (beech). Other pollen includes Quercus (oak), Carya (hickory), Pinus (pine), and Ulmus (elm) along with exotics. Overall the assemblage, except possibly for the high concentration of Fagus, indicates a warm-temperate climate during the time of deposition.
Skunnemunk Conglomerate (Middle Devonian)
Skunnemunk Conglomerate (Darton, 1894) - Grayish-purple to grayish-red, thin- to very thick bedded, locally cross-bedded, polymictic conglomerate and sandstone containing clasts of white vein quartz, red and green quartzite and sandstone, red and gray chert, and red shale; interbedded with medium-gray, thin-bedded sandstone and greenish-gray and grayish-red, mud-cracked shale. Conglomerate and sandstone matrix is primarily hematite and microcrystalline quartz. Conglomerate cobbles range to 16.5 cm (6.5 in) long, and average cobble size increases in upper part of unit. Lower contact conformable and gradational as defined by Kummel and Weller (1902). About 915 m (3,000 ft) thick.
Stockton Formation (Upper Triassic)
Stockton Formation (Kummel, 1897) - Light-gray, light-grayishbrown, yellowish- to pinkish-gray, or violet-gray to reddish-brown, medium- to coarse-grained arkosic sandstone and reddish- to purplish-brown mudstone, silty mudstone, argillaceous siltstone, and shale. Mudstone, siltstone and shale beds thicker and more numerous in central Newark basin west of Round Valley Reservoir. Sandstones mostly planar-bedded, with scoured bases containing pebble lags and mudstone rip-ups. Unit is coarser near Newark basin border fault, where poorly exposed, reddish-brown to pinkish-white, medium- to coarse-grained, feldspathic pebbly sandstone and conglomerate (Trss) and pebble to cobble quartzite conglomerate (Trscq). Maximum thickness of formation about 1,240 m (4,070 ft).
Stockton Formation (Upper Triassic)
Stockton Formation - Predominantly medium- to coarse-grained, light-gray, light-grayish-brown, or yellowish- to pinkish-gray arkosic sandstone and medium- to fine-grained, violet-gray to reddish-brown arkosic sandstone; with lesser, reddish to purplish-brown, silty mudstone, argillaceous siltstone, and shale. Some coarse-grained sandstone in lower part contains thick beds of conglomerate (Trsc) which have been mapped in the vicinity of Stockton. Sandstone, deposited in high-gradient stream channels, is mostly planar bedded with scoured bases containing pebble lags and mudstone rip-up clasts. Upper part of channel beds are burrowed. Large-scale trough crossbeds occur in some very coarse grained sandstone beds; smaller scale trough and climbing-ripple cross lamination occur in the upper part of channel sequences and in finer grained sandstone beds. Typical floodplain mudstones are irregularly thin bedded and extensively burrowed. Floodplain beds are thicker and more numerous in the central Newark basin, near the Delaware River. Thickness of the unit (including Trsc) near Stockton is about 1,240 m (4,068 ft).
Tinton Formation (Upper Cretaceous, upper Maastrichtian)
Tinton Formation - Sand, quartz, and glauconite in varying proportions, very clayey and locally indurated by siderite into hard, massive ledges. Sand is dark gray to dark yellow where unweathered; where weathered, siderite changes color of unit to orange brown because of iron oxides, and the formation is stained or cemented in exotic patterns. The Tinton crops out in the northern part of the central sheet from Sandy Hook, Monmouth County, to the northernmost part of the Roosevelt quadrangle, near Perrineville. Unit unconformably overlies the Red Bank Formation in the high hills of the northern Coastal Plain, most notably near Perrineville and Morganville, Monmouth County. In these updip areas, fine gravel, 1 cm (0.4 in) maximum diameter, or large shell concentrations are found along the basal contact. The typical basal bed is a massive, glauconitic (10-35 percent), fine to medium-grained quartz sand with scattered gravel. The massive character of the basal bed is the result of extensive bioturbation. Burrows, filled with glauconite sand of the Tinton, project down into the quartz sand of the underlying Red Bank Formation. At lower elevations downdip, the Tinton is less weathered, much darker, more glauconitic, and typically indurated. The type locality on Pine Brook at Tinton Falls, Monmouth County, is in this downdip area. At Tinton Falls, 7 to 8 m (23-26 ft) of the Tinton is exposed and has a higher glauconite content than in the updip area. Glauconite at Tinton Falls is light green to pale yellow, and many of the grains have a smooth polished surface that is almost lustrous. Thin sections of the Tinton reveal that many of the grains are oolitic (Owens and Sohl, 1973). X-ray analyses indicate the presence of mixed clay minerals; therefore, the unit is not pure glauconite. The Tinton Formation at Tinton Falls has scattered molds of calcitic fossils and aragonitic shells. Richards (1958) recorded 30 species of mollusks from the Tinton in this area. Of importance are Sphenodiscus lobatus, Cucullaea (Idonearca) littlei, and Scabrotrigonia cerulia. In New Jersey, Scabrotrigonia cerulia is restricted to the Tinton. All three species are common to the upper Maastrichtian Haustator bilira Zone of Sohl (in Owens and others, 1977). Strontium-isotope analysis on calcareous shells from the Tinton yielded ages of 66.2 to 65.6 Ma or a late Maastrichtian age (Sugarman and others, 1995).
Towaco Formation (Lower Jurassic)
Towaco Formation (Olsen, 1980) - Reddish-brown to brownish-purple, fine- to medium-grained micaceous sandstone, siltstone, and silty mudstone in upward-fining sequences 1 to 3 m (3-10 ft) thick. Distributed throughout formation are eight or more sequences of gray to greenish- or brownish-gray, fine-grained sandstone, siltstone and calcareous siltstone and black, microlaminated calcareous siltstone and mudstone containing diagnostic pollen, fish and dinosaur tracks. Sandstone is commonly trough cross laminated; siltstone is commonly planar laminated or bioturbated, but can be indistinctly laminated to massive. Thermally metamorphosed into hornfels where in contact with Hook Mountain Basalt. Conglomerate and conglomeratic sandstone with subrounded quartzite and quartz clasts in matrix of light-red sand to brownish-red silt (Jtc) interfingers with rocks of the Towaco Formation north and west of New Vernon. Maximum thickness is about 380 m (1,250 ft).
Towaco Formation Conglomerate and Sandstone facies (Lower Jurassic)
Towaco Formation Conglomerate and Sandstone facies - Conglomerate and conglomeratic sandstone with subrounded quartzite and quartz clasts in matrix of light-red sand to brownish-red silt (Jtc) interfingers with rocks of the Towaco Formation north and west of New Vernon.
Unnamed Formation at Cape May (upper Pliocene)
Unnamed Formation at Cape May - Interbedded gravel, sand, and clay, massive to thickbedded. Informal unit described from a corehole at the Cape May Airport. The lower 18.3 m (60 ft) consists of interbedded gravel; medium- to very coarse grained, poorly sorted sand; and thin to thick beds of medium- to dark-gray, very woody clay. Gravel clasts are typically less than 0.64 mm (0.025 in) in diameter. The upper 12.2 m (40 ft) consists of a thick-bedded, medium-gray, extensively bioturbated clay-silt, which is overlain by an extensively burrowed, fine- to medium-grained glauconitic (about 5 percent) quartz sand. Quartz and siliceous rock fragments compose most sand grains. Feldspar is present in most samples but usually constitutes less than 10 percent of the sand fraction. No calcareous macrofossils were found in the burrowed intervals. Unit is known only to occur on the Cape May peninsula where it lies within a large channel. The unit is about 60 m (197 ft) in maximum thickness. The contact with the underlying Belleplain Member of the Kirkwood Formation is sharp and unconformable; a basal gravel bed as much as 1 m (3 ft) thick is present along the contact. The pollen assemblage in the lower part of the unit is dominated by pine and oak with somewhat lesser amounts of hickory and basswood. Spruce, hemlock, beech, alder, and black gum are minor constituents. Traces of fir, willow, birch, and sweet gum are present, as is exotic Engelhardia. The nonarborial pollen are a Multisia-type composite of the present-day Andean provenance which indicate an exotic cool climate. The lower assemblage suggests a cool-temperate climatic regimen. The pollen assemblage in the upper beds is dominated by oak and hickory with minor amounts of basswood, sweet gum, pine, and Multisia-type composite. Traces of cedar, willow, birch, alder, grass, and Sphagnum spores also are present. This assemblage probably represents a temperate climatic regimen (Les Sirkin, Adelphi University, written commun., 1991). The low percentage of exotic species is characteristic of the late Pliocene, and therefore, the unnamed unit at Cape May may be equivalent to the Beaverdam Formation of the Delmarva Peninsula of Delaware, Maryland, and Virginia.
Vincentown Formation (upper Paleocene, Selandian)
Vincentown Formation - Upper part, sand, glauconite (35-40 percent) and quartz (60-65 percent), fine- to very fine grained, very clayey and silty, massive, dark-gray, bioturbated, very micaceous. Lower part, sand, massive, less micaceous and clayey, dark-gray-green. The lower 4.5 m (15 ft) of the formation is a fine- to medium-grained, clayey glauconite sand. Locally, there is an accumulation of disarticulated calcareous shells along the contact with the underlying Hornerstown Formation. These shells are commonly the brachiopod Oleneothyris harlani or the mollusk Gryphaea dissimilaris. Where the shell bed is absent it is difficult to separate glauconite sand of the basal part of the Vincentown from the underlying Hornerstown Formation, which also is a glauconite sand. Gamma logs through this interval show that there is a small gamma spike along the contact between the glauconite sands. The grain size decreases and the formation is significantly more clayey downdip. At Allaire State Park, Monmouth County (drillhole Allaire-C), for example, the bulk of the Vincentown is a clayey, very micaceous, dark-gray, slightly feldspathic quartz sand. Large fossils, which are abundant in the near-surface beds, are absent. In addition, the basal glauconite beds tend to thicken somewhat downdip. Farther basinward, the bulk of the formation is an unfossiliferous, gray-green to locally tan clayey silt or silty clay. Locally, a thin- to thick-bedded glauconite sand occurs at the base. In the thickest downdip section penetrated at Island Beach, the Vincentown is mostly a pale-gray to dark-gray clay-silt. No megafossils were observed in the Island Beach core. On the basis of geophysical log interpretations in the deepest subsurface, this unit has a maximum thickness of about 38 m (125 ft). The age of the Vincentown is best indicated by calcareous nannofossils, which indicate Zones NP 5 to NP 9 (Bybell, 1992). Common nannofossils from Zone NP 5 are Chiasmolithus bidens, Ellipsolithus distichus, Fasciculithus tympaniformis, Scapholithus fossilis, and Toweius eminens. Common nannofossils in Zone NP 9 are Biantholithus astralis, Chiasmolithus bidens, Discoaster multiradiatus, D. salisburgensis, Fasciculithus involutus, F. schaubii, F. thomasii, and Lophodolithus nascens. The upper part of the Vincentown falls within the upper part of Zone NP 9 and therefore is late Paleocene (Selandian) in age.
Vincentown Formation (upper Paleocene, Selandian)
Vincentown Formation - Sand, quartz, medium-grained, well- to poorly sorted, dusky-yellow to pale-gray; weathers orange brown or red brown, typically very glauconitic and clayey near base; glauconite decreases up section. Feldspar and mica are minor sand constituents. Unit best exposed in the Pemberton, New Egypt, and Mount Holly quadrangles of the central sheet where the overlying formations have been stripped away. The Vincentown Formation is as much as 30 m (98 ft) thick and averages 3 to 15 m (10-49 ft) in its subcrop belt. Where unweathered the unit is generally a shelly sand; where weathered the unit is largely a massive quartz sand. The unweathered sand of the Vincentown is exposed intermittently along the Manasquan River near Farmingdale, Monmouth County. The calcareous nature of the unweathered Vincentown was observed in several coreholes in the vicinity of Farmingdale. The contact with the underlying Hornerstown Formation is disconformable; locally shell beds (bioherms) up to 1.5 m (5 ft) thick are found along the contact. Shells in the bioherms are typical of a restricted environment and contain the brachiopod Oleneothyris harlani (Morton) in the lower beds and the oyster Pycnodonte dissimilaris in the upper beds. The basal contact and the Oleneothyris bioherms are exposed along Crosswicks and Lahaway Creeks and their tributaries. Where bioherms are absent, the basal contact is difficult to place within a sequence of glauconite beds. In general, glauconite beds of the Vincentown are darker gray than glauconite beds of the Hornerstown, and the Vincentown has more quartz sand. Upper beds of the Vincentown are as much as 12 m (39 ft) thick and are mostly silty, darkgray to green-gray, massive, glauconite sand that contains a small percentage of quartz. Calcarenite or coquina, characterized by an abundance of bryozoans, occurs locally along the western belt. These fossiliferous beds, 6 to 7.5 m (20-25 ft) thick, are best exposed along Shingle Run in the New Egypt quadrangle area and in streams that cross the Vincentown outcrop belt in the Pemberton quadrangle. Calcareous nannofossils, present in some Vincentown outcrops, are from Zones NP 5 (the Oleneothyris beds) and NP 9 (late Paleocene). Vincentown sediments are much more fossiliferous in the subsurface and contain Zones NP 5 through NP 9, inclusive. Therefore, the Vincentown corresponds in age with the Aquia Formation of Virginia and Maryland. Numerous studies of the foraminifera of the Vincentown from calcareous beds in the western outcrop belt indicate that the Vincentown includes the planktic foraminifera Zones P3b through P6a (Olsson and others, 1988). A potassium-argon age of 56.4 +/- 18 Ma was determined for basal beds near New Egypt, Ocean County (Owens and Sohl, 1973).
Wantage Sequence (Middle Ordovician)
Wantage Sequence (Monteverde and Herman, 1989) - Restricted, discontinuous sequence of interbedded limestone, dolomite, conglomerate, siltstone, and shale. Upper part is medium-yellowish-brown- to olive-gray-weathering, medium- to dark-gray, very fine to fine-grained, laminated to massive limestone and dolomite that grade down into underlying clastic rocks of lower part. Upper part locally absent. Lower part ranges from grayish-red, medium-gray, pale-brown, and greenish-gray to pale-green mudstone and siltstone containing disseminated subangular to subrounded chert-gravel, quartz-sand lenses, and chert-pebble conglomerate. Lower contact unconformable. Thickness ranges from 0 to 46 m (0-150 ft).
Wenonah Formation (Upper Cretaceous, upper Campanian)
Wenonah Formation - Sand, quartz and mica, fine-grained, silty and clayey, massive to thick-bedded, dark-gray to medium-gray; weathers light brown to white, extensively bioturbated, very micaceous, locally contains high concentrations of sand-sized lignitized wood and has large burrows of Ophiomorpha nodosa. Feldspar (5-10 percent) is a minor sand constituent. Unit crops out in a narrow belt from Sandy Hook Bay on the central sheet and pinches out southwest of Oldmans Creek, Salem County, on the southern sheet. Isolated outliers of the Wenonah are detached from the main belt in the central sheet area. Thickness is about 10 m (33 ft) in the northern part of the central sheet, 20 m (66 ft) in the southwestern part of the central sheet, and 7.5 m (25 ft) in the southern sheet. The Wenonah is gradational into the underlying Marshalltown Formation. A transition zone of several meters is marked by a decrease in mica and an increase in glauconite sand into the Marshalltown. Fossil casts are abundant in the Wenonah. Weller (1907) reported Flemingostrea subpatulata Hop Brook in the Marlboro quadrangle indicating a late Campanian age. Wolfe (1976) placed the Wenonah microflora in his CA5A assemblage, considered to be of late Campanian age. Kennedy and Cobban (1994) identified ammonites including Baculites cf. B. scotti, Didymoceras n. sp., Menuites portlocki, Nostoceras (Nostoceras) puzosiforme n. sp., Nostoceras (Nostoceras) aff. N. colubriformus, Parasolenoceras sp., Placenticeras placenta, P. minor n. sp., and Trachyscaphites pulcherrimus. The presence of M. portlocki and T. pulcherrimus indicates late, but not latest, Campanian.
Wildwood Member of the Kirkwood Formation (middle and lower Miocene, Langhian and Burdigalian)
Wildwood Member - Clay, silty, massive to finely bedded, dark-gray to olive-gray, locally interbedded with thin beds of light-colored sand. Contains small shell fragments primarily at base. Upper beds are more sandy than lower beds but also contain many thin to thick beds of clay. The sand is fine to medium grained, light gray, and commonly has dispersed wood fragments. Shell fragments are locally present in this facies. Basal beds are micaceous, locally diatomaceous, and contain wood fragments. Quartz is the major sand constituent with minor amounts of siliceous rock fragments and feldspar. The Wildwood subcrops beneath surficial deposits where the Belleplain Member and Cohansey Formation were stripped away. Along Delaware Bay, the Wildwood subcrops from near the Cohansey River to Fortescue, Cumberland County. Along the Atlantic Coast, the unit subcrops from Bay Shore Park to near Beach Haven Park, Ocean County. The maximum thickness of the unit is about 18 m (59 ft). The contact with the underlying Shiloh Marl Member is sharp and unconformable. Diatoms from the Wildwood Member are from the East Coast Diatom Zone (ECDZ) 2 of Andrews (1988) indicating a latest Burdigalian and Langhian age (late early and early middle Miocene).
Wildwood Member of the Kirkwood Formation (middle and lower Miocene, Langhian and Burdigalian)
Wildwood Member - New member named for a well drilled at Wildwood, Cape May County. Typically consists of a very fossiliferous, micaceous, darkgray clay-silt interbedded with fine- to medium-grained, pale-gray-brown sand in lower half of the member. The upper half of the member is more sandy (mostly fine-grained, micaceous quartz sand), thin-bedded to laminated, commonly interbedded with thin-bedded, gray-brown, micaceous clay; wood fragments are common. The basal contact with the underlying unit is sharp and has considerable relief. A 1-m (3-ft)-thick bed of gravel (1 cm (0.4 in) in maximum diameter) with pieces of quartz and worn shells, commonly occurs along the contact. Thickness of the unit varies widely because of the undulating basal contact. The maximum thickness, 80 m (262 ft), was penetrated in the Wildwood well. At the Island Beach well (290019) at Island Beach State Park, Ocean County, the Wildwood is over 30 m (98 ft) thick. The lower 6 m (20 ft) consists of thick interbeds of fine- to medium-grained, massive to locally thick-bedded, extensively bioturbated, micaceous quartz sand and dark-brown and grayish-brown silty clay. The middle part is mostly massive to finely laminated, dark-gray to gray-brown silt to clay. The upper 6 m (20 ft) consists of fine- to coarse-grained, locally gravelly, thin- to thick-bedded sand interbedded with the clay and silt. The age of the Wildwood was determined from diatoms and strontium-isotope age estimates of mollusk shells. The diatom assemblages in this unit fall within Andrews (1988) ECDZ 2, thus indicating a considerable unconformity between this member and the overlying Belleplain (ECDZ 6). ECDZ 2 is in the Delphineis ovata Zone and contains the characteristic diatoms Coscinodiscus lewisianus, Delphineis lineata, Rhaphidodiscus marylandicus, Rhaphoneis fusiformis, R. margaritata, R. wicomicoensis, Sceptroneis caduceus, S. grandis, and S. hungarica. Strontium-isotope analyses on shells from this interval indicate an age range of 17.4 to 15.5 Ma (Sugarman and others, 1993). The isotopic and paleontologic ages suggest that the Wildwood Member straddles the early-middle Miocene boundary (Langhian-Burdigalian boundary). Pollen from the Wildwood has warm-temperate affinities in the lower part and mixed warm- and cool-temperate affinities in the upper part suggesting an overall cooling of the climate during the time of deposition. Collectively, the Wildwood and Belleplain Members constitute the section that Woolman (1889-1902) assigned to his "great diatom bed".
Wissahickon Formation (Lower Cambrian and Late Proterozoic)
Wissahickon Formation - Fine- to medium-grained biotite-quartz-plagioclase schist and gneiss that contains thin amphibolite layers. Schist and gneiss in alternating layers suggest a turbidite sequence of shale and graywacke. The rocks are at high metamorphic grade, and, in places, the more pelitic parts have partly melted forming veins of migmatite. Some exposures show evidence of polymetamorphism as micaceous minerals occur both within the schistosity and as static porphyroblasts.
Woodbury Formation (Upper Cretaceous, lower Campanian)
Woodbury Formation - Clay-silt, dark-gray; weathers brown and orange pink. Iron oxides fill fractures or form layers in the most weathered beds. Unit is massive except at the base where thin quartz sand layers occur. Locally, thin stringers of pale-greenish-brown, smooth-surface glauconite occur near the top. Unit conspicuously micaceous throughout and contains finely dispersed pyrite, carbonaceous matter, and small pieces of carbonized wood as much as 30 cm (12 in) in length. Small siderite concretions are abundant in the Woodbury in the northern part of the outcrop belt. Unit forms a broad belt in the central sheet from Sandy Hook Bay, southwest to area around East Greenwich, Gloucester County, where it pinches out or changes facies. The Woodbury maintains a thickness of about 15 m (49 ft) throughout most of its outcrop belt. Fossil imprints are abundant. An extensive Woodbury macrofauna was described by Weller (1907) from siderite concretions from a tributary to the Cooper River in the Camden quadrangle. This assemblage is unusual in that it is the only existing outcrop of the Woodbury where calcareous and aragonitic shells are still intact. Most fossils are small, fragmented, and concentrated in small pockets, but larger intact calcareous fossils are scattered throughout the Woodbury. Weller (1907) recorded 57 species from this locality. In addition, this is the same locality that contains fossils of the dinosaur Hadrosaurus foulkii. Pollen collected from the Woodbury was assigned to the CA3 Zone by Wolfe (1976). Biostratigraphic data suggest that the Woodbury is of early Campanian age.
New Mexico
Abo and Yeso Formations (Phanerozoic | Paleozoic | Permian)
Abo and Yeso Formations, undivided
Abo Formation (Phanerozoic | Paleozoic | Permian)
Abo Formation; red beds, arkosic at base, finer and more mature above; Wolfcampian; may include limestone beds of Pennsylvanian age (Virgilian) in Zuni Mountains. In Robledo Mountains the Abo may be considered a member of the Hueco Formation
Abo Formation, lower part (Phanerozoic | Paleozoic | Permian)
Lower part of Abo Formation; Wolfcampian, and in part Virgilian ?
andesite and basaltic andesite flows and associated volcaniclastic units (Phanerozoic | Cenozoic | Tertiary)
Lower Tertiary, (Lower Oligocene and Eocene) andesite and basaltic andesite flows, and associated volcaniclastic units. Includes Rubio Peak Formation, and andesite of Dry Leggett Canyon
andesites and basaltic andesites (Phanerozoic | Cenozoic | Tertiary)
Upper Oligocene andesites and basaltic andesites (26-29 Ma); includes La Jara Peak Basaltic Andesite, Uvas Basalt, the basaltic andesite of Poverty Creek, and Squirrel Springs Andesite, the Razorback, Bear Springs Canyon, Salt Creek, Gila Flat, and Middle Mountain Formations, and the Alum Mountain Group; locally includes more silicic flows
Animas Formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary)
Animas Formation; in northeast San Juan Basin
Artesia Group (Phanerozoic | Paleozoic | Permian)
Artesia Group; shelf facies forming broad south-southeast trending outcrop from Glorieta to Artesia area; includes Grayburg, Queen, Seven Rivers, Yates, and Tansill Formations; Guadalupian. May locally include Moenkopi Formation (Triassic) at top
Bandelier Tuff (Phanerozoic | Cenozoic | Quaternary)
Bandelier Tuff; Jemez Mountains area only
basaltic and andesitic volcanics interbedded with sedimentary units (Phanerozoic | Cenozoic | Tertiary Quaternary)
Basaltic and andesitic volcanics interbedded with Pleistocene and Pliocene sedimentary units
basaltic andesites (Phanerozoic | Cenozoic | Tertiary)
Lower Miocene and uppermost Oligocene basaltic andesites (22-26 Ma). Includes Bearwallow Mountain Andesite and basaltic andesite of Mangas Mountain
basalt or basaltic andesite (Phanerozoic | Cenozoic | Quaternary)
Basalt or basaltic andesite; middle and lower Pleistocene
Bell Canyon Formation (Phanerozoic | Paleozoic | Permian)
Bell Canyon Formation; basin facies-sandstone, limestone, and shale; Guadalupian
Bull Canyon Formation of Chinle Group (Phanerozoic | Mesozoic | Triassic)
Bull Canyon Formation; Norian
Bursum Formation (Phanerozoic | Paleozoic | Permian)
Bursum Formation; shale, arkose, and limestone; earliest Permian
Carlile Shale (Phanerozoic | Mesozoic | Cretaceous)
Carlile Shale; limited to northeastern area; Turonian-Coniacian
Cherry Canyon Formation (Phanerozoic | Paleozoic | Permian)
Cherry Canyon Formation; basin facies-sandstone, limestone, and shale
Chinle Group (Phanerozoic | Mesozoic | Triassic)
Chinle Group; Upper Triassic; includes Moenkopi Formation (Middle Triassic) at base in many areas; in eastern part of state the following five formations are mapped:
Cretaceous rocks, undivided (Phanerozoic | Mesozoic | Cretaceous)
Cretaceous rocks, undivided
Cutler Formation (Phanerozoic | Paleozoic | Permian)
Cutler Formation; used in northern areas and Chama embayment only
Dakota Sandstone and Rio Salado Tongue of the Mancos Shale (Phanerozoic | Mesozoic | Cretaceous)
Dakota Sandstone and Rio Salado Tongue of the Mancos Shale. In northwest Socorro County locally includes overlying Tres Hermanos Formation
felsic shallow-intrusive rocks (Phanerozoic | Cenozoic | Tertiary)
Middle Tertiary felsic shallow-intrusive rocks; phonolites and trachytes of northeastern N.M.; includes the rhyolite of Ash Mountain
Fence Lake Formation (Phanerozoic | Cenozoic | Tertiary)
Fence Lake Formation; conglomerate and conglomeratic sandstone, coarse fluvial volcanoclastic sediments, minor eolian facies, and pedogenic carbonates of the southern Colorado Plateau region; Miocene
Garita Creek Formation of Chinle Group (Phanerozoic | Mesozoic | Triassic)
Garita Creek Formation; Carnian
Gila Group (Phanerozoic | Cenozoic | Tertiary Quaternary)
Gila Group. Includes Mimbres Formation and several informal units in southwestern basins; Middle Pleistocene to uppermost Oligocene
Grayburg and Queen Fromations (Phanerozoic | Paleozoic | Permian)
Grayburg and Queen Formations; sandstone, gypsum, anhydrite, dolomite, and red mudstone; Guadalupian
Greenhorn Formation and Carlile Shale (Phanerozoic | Mesozoic | Cretaceous)
Greenhorn Formation and Carlile Shale, undivided; locally includes Graneros Shale
Hinsdale Basalt (Phanerozoic | Cenozoic | Tertiary)
Hinsdale Basalt; northern Taos and eastern Rio Arriba Counties; basalt flows interbedded with Los Pinos Formation
Hueco Formation (Phanerozoic | Paleozoic | Permian)
Hueco Formation; limestone unit restricted to south-central area; Pendejo Tongue divides Abo Formation into upper and lower parts; Wolfcampian
intertongued Dakota-Mancos sequence (Phanerozoic | Mesozoic | Cretaceous)
Intertongued Dakota-Mancos sequence of west-central New Mexico; includes the Whitewater Arroyo Tongue of Mancos Shale and the Twowells Tongue of the Dakota
Kirtland and Fruitland Formations (Phanerozoic | Mesozoic | Cretaceous)
Kirtland and Fruitland Formations; coal-bearing, coal primarily in the Fruitland; Campanian to Maastrichtian
lacustrine and playa-lake deposits (Phanerozoic | Cenozoic | Quaternary)
Lacustrine and playa-lake deposits; includes associated alluvial and eolian deposits of major lake basins; upper Quaternary
Lead Camp Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Lead Camp Formation; San Andres and Organ Mountains
Lewis Shale (Phanerozoic | Mesozoic | Cretaceous)
Lewis Shale; marine shale and mudstone
Los Pinos Formation of Lower Santa Fe Group (Phanerozoic | Cenozoic | Tertiary)
Los Pinos Formation of Lower Santa Fe Group (Miocene and upper Oligocene); includes Carson Conglomerate (Dane and Bachman, 1965) in Tusas Mountains-San Luis Basin area
Lower and Middle Santa Fe Group (Phanerozoic | Cenozoic | Tertiary)
Lower and Middle Santa Fe Group. Includes Hayner Ranch, Rincon Valley, Popotosa, Cochiti, Tesuque, Chamita, Abiquiu, and other Formations; Miocene and uppermost Oligocene
Mancos Formation and Beartooth Quartzite (Phanerozoic | Mesozoic | Cretaceous)
Mancos Formation and Beartooth Quartzite (and Sarten Sandstone); Mancos includes what was formerly referred to as Colorado Shale which in turn may include equivalents of Tres Hermanos Formation
McRae Formation (Phanerozoic | Mesozoic | Cretaceous)
McRae Formation; Engle basin - Cutter sag area; Maastrichtian
Menefee Formation (Phanerozoic | Mesozoic | Cretaceous)
Menefee Formation; mudstone, shale, and sandstone; coal-bearing
Mesaverde Group (Phanerozoic | Mesozoic | Cretaceous)
Mesaverde Group includes the Gallup Sandstone, Crevasse Canyon Formation, Point Lookout Sandstone, Menefee Formation, and Cliff House Sandstone
metamorphic rocks (Proterozoic | Paleoproterozoic)
Lower Proterozoic metamorphic rocks, dominantly felsic volcanic, volcaniclastic and plutonic rocks (1650-1700+ Ma); includes Vadito Group; locally includes high-grade felsic gneisses of unknown age
Moenkopi Formation (Phanerozoic | Mesozoic | Triassic)
Moenkopi Formation; Middle Triassic
Moreno Hill Formation and Atarque Sandstone (Phanerozoic | Mesozoic | Cretaceous)
Moreno Hill Formation and Atarque Sandstone; in Salt Lake coal field and extreme southern Zuni basin; Turonian
Morrison Formation and upper San Rafael Group (Phanerozoic | Mesozoic | Jurassic)
Morrison Formation and upper San Rafael Group
Nacimiento Formation (Phanerozoic | Cenozoic | Tertiary)
Nacimiento Formation; Paleocene, San Juan Basin
Ogallala Formation (Phanerozoic | Cenozoic | Tertiary)
Ogallala Formation, alluvial and eolian deposits, and petrocalcic soils of the southern High Plains; Lower Pliocene to middle Miocene (locally includes unit Qoa)
Ojo Alamo Formation (Phanerozoic | Cenozoic | Tertiary)
Ojo Alamo Formation; Paleocene, San Juan Basin
Panther Seep Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Panther Seep Formation; Organ, Franklin, and San Andres Mountains
Pennsylvanian rocks, undivided (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Pennsylvanian rocks, undivided; in Sangre de Cristo Mountains may include Sandia Formation, Madera Limestone, La Pasada, Alamitos, and Flechado Formations; elsewhere may include Bar-B, Nakaye, Red House, Oswaldo, and Syrena Formations
Pierre Shale and Niobrara Formation (Phanerozoic | Mesozoic | Cretaceous)
Pierre Shale and Niobrara Formation
Poison Canyon and Raton Fromations (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary)
Poison Canyon and Raton Formations; undivided
Quartermaster Formation (Phanerozoic | Paleozoic | Permian)
Quartermaster Formation; red sandstone and siltstone; Upper Permian
Quatermaster and Rustler Formations (Phanerozoic | Paleozoic | Permian)
Quartermaster and Rustler Formations; Upper Permian
Raton Formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary)
Raton Formation; in Raton Basin; unit contains conformable K/T boundary
Redonda Formation of Chinle Group (Phanerozoic | Mesozoic | Triassic)
Redonda Formation
rhyolitic pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary)
Upper Oligocene rhyolitic pyroclastic rocks (ash-flow tuffs); includes Davis Canyon Tuff, South Crosby Peak Formation, La Jencia, Vick's Peak, Lemitar, South Canyon, Bloodgood Canyon, Shelley Peak Tuffs, tuff of Horseshoe Canyon, Park Tuff, Rhyolite Canyon Tuff, Apache Springs Tuff, Diamond Creek, Jordan Canyon, Garcia Camp Tuffs, the Turkey Springs Tuff, the tuff of Little Mineral Creek, the Amalia Tuff, and others. Some contain volcaniclastic and reworked volcaniclastic rocks, and eolian sandstone; (24-29 Ma)
Rustler Formation (Phanerozoic | Paleozoic | Permian)
Rustler Formation; siltstone, gypsum, sandstone, and dolomite; Upper Permian
San Andres Formation (Phanerozoic | Paleozoic | Permian)
San Andres Formation; limestone and dolomite with minor shale; Guadalupian in south, in part Leonardian to north
San Andres Limestone and Glorieta Sandstone (Phanerozoic | Paleozoic | Permian)
San Andres Limestone and Glorieta Sandstone; Guadalupian and Leonardian
Sandia Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian)
Sandia Formation; predominately clastic unit (commonly arkosic) with minor black shales, and limestone in lower part; locally includes Osha Canyon Formation in Nacimiento Mountains
Sangre de Cristo Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian)
Sangre de Cristo Formation, in Sangre de Cristo Mountains
San Rafael Group (Phanerozoic | Mesozoic | Jurassic)
San Rafael Group; consists of Entrada Sandstone, Todilto and Summerville Formations, Bluff Sandstone, and locally Zuni Sandstone (or only Acoma Tongue of Zuni)
Santa Fe Group (Phanerozoic | Cenozoic | Tertiary Quaternary)
Santa Fe Group, undivided. Basin fill of Rio Grande rift region; middle Pleistocene to uppermost Oligocene
Santa Rosa Formation of Chinle Group (Phanerozoic | Mesozoic | Triassic)
Santa Rosa Formation; Carnian; includes Moenkopi Formation (Middle Triassic) at base in most areas
sedimentary and vocaniclastic sedimentary rocks (Phanerozoic | Cenozoic | Tertiary)
Mostly Oligocene and upper Eocene sedimentary and volcaniclastic sedimentary rocks with local andesitic to intermediate volcanics; includes Espinaso, Spears, Bell Top, and Palm Park Formations
sedimentary units, Palogene (Phanerozoic | Cenozoic | Tertiary)
Paleogene sedimentary units; includes Baca, Galisteo, El Rito, Blanco Basin, Love Ranch, Lobo, Sanders Canyon, Skunk Ranch, Timberlake, and Cub Mountain Formations
Seven Rivers Formation (Phanerozoic | Paleozoic | Permian)
Seven Rivers Formation; gypsum, anhydrite, salt, dolomite, and siltstone; Guadalupian
silicic flows and massess and associated pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary)
Upper Oligocene silicic (or felsic) flows and masses and associated pyroclastic rocks; includes Taylor Creek, Fanney, and Rocky Canyon Rhyolites
silicic flows, domes, and associated pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary)
Lower Oligocene silicic (or felsic) flows, domes, and associated pyroclastic rocks and intrusions; includes Mimbres Peak Formation
silicic pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary)
Lower Oligocene silicic pyroclastic rocks (ash-flow tuffs); includes Hell's Mesa, Kneeling Nun, lower part of Bell Top Formation, Caballo Blanco, Datil Well, Leyba Well, Rock House Canyon, Blue Canyon, Sugarlump and Tadpole Ridge Tuffs, the tuffs of the Organ cauldron, Treasure Mountain Tuff (now known as Chiquito Peak Tuff), Bluff Creek Tuff, Oak Creek Tuff, tuff of Steins Mountain, tuff of Black Bill Canyon, tuff of Farr Ranch, Woodhaul Canyon, Gillespie and Box Canyon Tuffs, Cooney Tuff, and other volcanic and interbedded fluvial and pumiceous units; (31-36.5 Ma)
Trujillo Formation of Chinle Group (Phanerozoic | Mesozoic | Triassic)
Trujillo Formation; Norian
undivided, Upper Cretaceous (Phanerozoic | Mesozoic | Cretaceous)
Upper Cretaceous, undivided. Includes Virden Formation in northern Hidalgo County, Ringbone Formation in Hidalgo and Luna and Grant Counties, and locally Beartooth and Sarten, Mancos in Silver City area; Cenomanian - Maastrichtian for most part, although Beartooth is pre-Cenomanian
upper Chinle Group (Garita Creek, Trujillo, Bull Canyon, and Redonda Formations) (Phanerozoic | Mesozoic | Triassic)
Upper Chinle Group, Garita Creek through Redonda Formations, undivided
Upper Santa Fe Group (Phanerozoic | Cenozoic | Tertiary Quaternary)
Upper Santa Fe Group. Includes Camp Rice, Fort Hancock, Palomas, Sierra Ladrones, Ancha, Puye, and Alamosa Formations; middle Pleistocene to uppermost Miocene
upper Tertiary sedimentary units (Phanerozoic | Cenozoic | Tertiary)
Upper Tertiary sedimentary units; includes Bidahochi Formation, the Picuris Formation, and Las Feveras Formation, and locally fanglomerates; Pliocene to upper Miocene
Vermejo Formation and Trinidad Sandstone (Phanerozoic | Mesozoic | Cretaceous)
Vermejo Formation and Trinidad Sandstone; Maastrichtian
volcanic rocks, lower Oligocene and Eocene (Phanerozoic | Cenozoic | Tertiary)
Lower Oligocene and Eocene volcanic rocks, undifferentiated; dominantly intermediate composition, with interbedded volcaniclastic rocks; (31-44 Ma)
Yates and Tansill Formations (Phanerozoic | Paleozoic | Permian)
Yates and Tansill Formations; sandstone, siltstone, limestone, dolomite, and anhydrite; Guadalupian
Yesa Formation (Phanerozoic | Paleozoic | Permian)
Yeso Formation; sandstones, siltstones, anhydrite, gypsum, halite, and dolomite; Leonardian
Yeso, Glorieta, and San Andres Formations, undivided (Phanerozoic | Paleozoic | Permian)
Yeso, Glorieta and San Andres Formations, undivided
Nevada
Alluvial deposits (Quaternary)
ALLUVIAL DEPOSITS-Locally includes beach and sand dune deposits
Andesite and basalt flows (Early Miocene to Early Pliocene)
ANDESITE AND BASALT FLOWS-Mostly in about 17 to about 6 m.y. age range. In Humboldt County, locally includes rocks as old as 21 m.y. May include rocks younger than 6 m.y. in places
Andesite and related rocks of intermediate composition (Early Oligocene to Early Miocene)
ANDESITE AND RELATED ROCKS OF INTERMEDIATE COMPOSITION-Flows and breccias
Andesite and related rocks of intermediate composition (Late Miocene to Middle Miocene)
ANDESITE AND RELATED ROCKS OF INTERMEDIATE COMPOSITION-Flows and breccias
Antler Sequence of Silberling and Roberts (1962) (Pennsylvanian to Late Permian )
ANTLER SEQUENCE OF SILBERLING AND ROBERTS (1962) (Middle Pennsylvanian to Early or Late Permian) (Guadalupian)-Conglomerate, sandy to conglomeratic limestone, limestone, sandstone, and calcareous shale. Thin detrital and carbonate sequence within main part of Antler orogenic belt. Includes units such as Sunflower Formation of Bushnell (1967) in Elko County, Battle Formation, Antler Peak Limestone, and Edna Mountain Formation in Lander and western Eureka Counties, and Wildcat Peak Formation in northern Nye County
Argillaceous limestone, chert, and shale (Devonian)
ARGILLACEOUS LIMESTONE, CHERT, AND SHALE-Elko and Eureka Counties
Ash-flow tuffs and tuffaceous sedimentary rocks (Middle Miocene to Late Miocene)
ASH-FLOW TUFFS AND TUFFACEOUS SEDIMENTARY ROCKS
Ash-flow tuffs, rhyolitic flows, and shallow intrusive rocks (Middle Miocene to Late Miocene)
ASH-FLOW TUFFS, RHYOLITIC FLOWS, AND SHALLOW INTRUSIVE ROCKS
Banbury Formation (Middle Miocene to Late Miocene)
BANBURY FORMATION-Basalt, gravel, and tuffaceous sediments locally. Northeast Humboldt County and northwest Elko County
Basalt flows (Miocene to Quaternary)
BASALT FLOWS-Locally includes maar deposits
Breccia (Middle Eocene to Early Pliocene)
BRECCIA-Volcanic, thrust, and jasperoid breccia and landslide megabreccia
Chert, shale, argillite, siltstone, quartzite, and greenstone (Cambrian to Devonian)
CHERT, SHALE, ARGILLITE, SILTSTONE, QUARTZITE, AND GREENSTONE-Undivided siliceous assemblage. Mostly Ordovician
Cherty limestone and sparse dolomite, shale, and sandstone (Permian)
CHERTY LIMESTONE AND SPARSE DOLOMITE, SHALE, AND SANDSTONE (Lower and Upper Permian)-Includes units such as Park City Group and equivalent rocks in northern Nevada and Toroweap Formation and Kaibab Limestone in southern Nevada
Chinle Formation and associated rocks (Late Triassic)
CHINLE FORMATION AND ASSOCIATED ROCKS (Upper Triassic)-Continental deposits of variegated bentonitic claystone, siltstone, and clayey sandstone; ledge-forming sandstone; and red siltstone
Conglomerate, limestone, meta-andesite, phyllite, and shale (Devonian to Mississippian)
CONGLOMERATE, LIMESTONE, META-ANDESITE, PHYLLITE, AND SHALE-Includes Grossman, Banner, Nelson, and Mountain City Formation. Northern Elko County
Conglomerate, sandstone, shale, and dolomite of Diablo Formation below and shale, sandstone, and conglomerate of Candelaria Formation above (Early Permian to Early Triassic)
CONGLOMERATE, SANDSTONE, SHALE, AND DOLOMITE OF DIABLO FORMATION BELOW AND SHALE, SANDSTONE, AND CONGLOMERATE OF CANDELARIA FORMATION ABOVE (Lower or Upper Permian to Lower Triassic)-Mineral, Esmeralda, and northwestern Nye Counties
Continental deposits of siltstone, shale, conglomerate, and limestone (Cretaceous)
CONTINENTAL DEPOSITS OF SILTSTONE, SHALE, CONGLOMERATE, AND LIMESTONE-Includes units such as King Lear Formation in Humboldt County, Newark Canyon Formation in Eureka County, Willow Tank Formation and baseline Sandstone in Clark County
Continental sedimentary rocks (Late Cretaceous to Eocene)
CONTINENTAL SEDIMENTARY ROCKS-Includes units such as Pansy Lee Conglomerate in Humboldt County, part of Cretaceous(?) and Tertiary rocks of Kleinhampl and Ziony (1967) in northern Nye County, and part of "older clastic rocks" of Tschanz and Pampeyan (1970) in Lincoln County
Continental sedimentary rocks (Late Cretaceous to Early Miocene)
CONTINENTAL SEDIMENTARY ROCKS-Clark County
Diorite (Jurassic to Cretaceous)
Dolomite (Silurian to Early Devonian)
DOLOMITE-Includes units such as Laketown and Lone Mountain Dolomites. Locally includes rocks of Early Devonian age at top.
Dolomite (Late Ordovician to Late Silurian)
DOLOMITE-Includes uppermost part of Ordovician System (Ely Springs Dolomite and equivalent rocks) and all of Silurian System.
Dolomite and limestone (Middle Cambrian to Ordovician)
DOLOMITE AND LIMESTONE-Undivided Cambrian and Ordovician rocks in part of Clark County; mostly Cambrian.
Dolomite and limestone (Middle Cambrian to Devonian)
DOLOMITE AND LIMESTONE (Lower Paleozoic)
Dolomite, limestone, and minor amounts of sandstone and quartzite (Devonian)
DOLOMITE, LIMESTONE, AND MINOR AMOUNTS OF SANDSTONE AND QUARTZITE-Includes units such as Sevy and Simonson Dolomites, Guilmette and Nevada Formations, and Devils Gate Limestone.
Dunlap Formation (Early Jurassic to Middle Jurassic)
DUNLAP FORMATION (Lower and Middle Jurassic)-Conglomerate, sandstone, greenstone, felsite, and tuff. Locally contemporaneous with folding and thrusting. Mineral County and adjacent parts of Esmeralda and Nye Counties
Elder Sandstone (Silurian)
ELDER SANDSTONE-Feldspathic sandstone, siltstone, shale, and chert. Lander County.
Gabbroic complex (Early Jurassic to Middle Jurassic)
GABBROIC COMPLEX (Lower and Middle Jurassic)-Includes gabbro, basalt, and synorogenic quartz sandstone (Boyer Ranch Formation). Churchill and Pershing Counties
Granitic rocks (Jurassic)
GRANITIC ROCKS-Mostly quartz monzonite and granodiorite
Granitic rocks (Middle Triassic to Early Jurassic)
GRANITIC ROCKS-Quartz monzonite in northern Esmeralda County
Granitic rocks (Paleocene to Late Miocene)
GRANITIC ROCKS-Mostly quartz monzonite and granodiorite
Granitic rocks (Cretaceous)
GRANITIC ROCKS-Mostly quartz monzonite and granodiorite
Granitic rocks, central and eastern Nevada (Jurassic to Miocene)
GRANITIC ROCKS, CENTRAL AND EASTERN NEVADA-Mostly quartz monzonite and granodiorite. Inconclusively dated or not dated radiometrically
Granitic rocks, western Nevada (Jurassic to Cretaceous)
GRANITIC ROCKS, WESTERN NEVADA (Mesozoic)-Mostly quartz monzonite and granodiorite. Inconclusively dated or not dated radiometrically
Harmony Formation (Late Cambrian)
HARMONY FORMATION (Upper Cambrian)-Feldspathic and arkosic sandstone and minor amounts of shale, limestone, and chert.
Havallah sequence of Silberling and Roberts (1962) (Mississippian to Permian)
HAVALLAH SEQUENCE OF SILBERLING AND ROBERTS (1962)-Chert, argillite, shale, greenstone, and minor amounts of siltstone, sandstone, conglomerate, and limestone. Includes Schoonover Formation of Fagan (1962) and Reservation Hill Formation in Elko County, Farrel Canyon Formation in southwestern Humboldt County, Havallah and Pumpernickel Formations in Pershing, Lander, and parts of Humboldt Counties, and rocks originally considered a part of the Pablo and Excelsior Formations in northern Nye, northern Esmeralda, and southern Mineral Counties. Assignment of some rocks to the Havallah sequence in the East Range, Pershing County, is highly uncertain. Includes rocks ranging in age from Late Mississippian to Early Permian
Horse Spring Formation (Late Oligocene to Middle Miocene)
HORSE SPRING FORMATION-Tuffaceous sedimentary rocks, southern Nevada
Igneous and metamorphic complex (Paleozoic sedimentary rocks with Mesozoic intrusive rocks)
IGNEOUS AND METAMORPHIC COMPLEX-Pegmatitic granite and other granitic rocks complexly intermixed with metasedimentary rocks. Considered to be Mesozoic igneous complex intruding lower Paleozoic and possibly Precambrian Z sedimentary rocks. Grades into units shown on map as lower Paleozoic. Ruby Mountains and East Humboldt Range, Elko County
Intrusive rocks (Late Cretaceous to Middle Miocene)
INTRUSIVE ROCKS-Aphanitic, porphyritic, and coarsely granular rocks ranging in composition from diorite to granite. Clark County
Intrusive rocks of mafic and intermediate composition (Miocene to Quaternary)
INTRUSIVE ROCKS OF MAFIC AND INTERMEDIATE COMPOSITION
Intrusive rocks of mafic to intermediate composition (Eocene to Miocene)
INTRUSIVE ROCKS OF MAFIC TO INTERMEDIATE COMPOSITION
Koipato Group and related rocks (Permian to Early Triassic)
KOIPATO GROUP AND RELATED ROCKS (Lower Triassic)-Altered andesitic flows, rhyolitic tuffs and flows, and clastic rocks. Includes rocks mapped by Silberling (1959) as Pablo Formation and originally considered to be Permian in the Shoshone Mountains, Nye County. Includes Tallman Fanglomerate (Permian?) in Humboldt County
Landslide deposits (Quaternary)
LANDSLIDE DEPOSITS
Limestone and dolomite, locally thick sequences of shale and siltstone (Late Cambrian to Middle Cambrian)
LIMESTONE AND DOLOMITE, LOCALLY THICK SEQUENCES OF SHALE AND SILTSTONE-Includes units such as Pioche Shale, Eldorado Dolomite, Geddes Limestone, Secret Canyon Shale, Hamburg Dolomite, Dunderberg Shale, and Windfall Formation of northern Nevada and Carrara, Bonanza King, and Nopah Formations of southern Nevada.
Limestone and minor amounts of dolomite and shale (Mississippian)
LIMESTONE AND MINOR AMOUNTS OF DOLOMITE AND SHALE-Includes units such as Rogers Spring and Monte Cristo Limestones
Limestone and sparse dolomite, siltstone, and sandstone (Mississippian to Early Permian)
LIMESTONE AND SPARSE DOLOMITE, SILTSTONE, AND SANDSTONE-Includes units such as undivided Riepe Spring Limestone of Steele (1960) and Ely Limestone or their equivalent in Elko, White Pine, and northern Lincoln Counties and most of the Bird Spring Formation and Callville Limestone in Clark and southern Lincoln Counties. Includes some stratigraphically higher Permian rocks in Leppy Peak, easternmost Elko County.
Limestone, dolomite, and shale (Mississippian to Permian)
LIMESTONE, DOLOMITE, AND SHALE (Upper Paleozoic)-Includes Van Duzer Limestone of Decker (1962)
Limestone, dolomite, shale, and quartzite (Ordovician)
LIMESTONE, DOLOMITE, SHALE, AND QUARTZITE-Includes units such as Pogonip Group, Eureka Quartzite, and Ely Springs Dolomite. Where Ely Springs Dolomite or equivalent rocks are included in SOc unit, this unit includes only the Pogonip Group and Eureka Quartzite or their equivalents.
Limestone, minor amounts of dolomite, shale, and sandstone; locally thick conglomerate units (Triassic)
LIMESTONE, MINOR AMOUNTS OF DOLOMITE, SHALE, AND SANDSTONE; LOCALLY THICK CONGLOMERATE UNITS (Lower, Middle, and Upper Triassic)-Includes Tobin, Dixie Valley, Favret, Augusta Mountain, and Cane Spring Formations and Star Peak Group in central Nevada and Grantsville and Luning Formations in west-central Nevada
Massive limestone (Mississippian)
MASSIVE LIMESTONE-In the San Antonio Mountains, western Nye County
Metamorphic rocks (Early Proterozoic)
METAMORPHIC ROCKS-Gneiss and schist and lesser amounts of gneissic granite, pyroxenite, hornblendite, migmatite, pegmatite, and marble.
Moenkopi Formation, Thaynes Formation, and related rocks (Early Triassic to Middle Triassic)
MOENKOPI FORMATION, THAYNES FORMATION, AND RELATED ROCKS (Lower Triassic)-Marine deposits of siltstone, limestone, and sparse conglomerate
Phyllitc siltstone, quartzite, and lesser amounts of limestone and dolomite (Late Proterozoic to Early Cambrian)
PHYLLITIC SILTSTONE, QUARTZITE, AND LESSER AMOUNTS OF LIMESTONE AND DOLOMITE-Includes Reed Dolomite; Deep Spring, Campito, Poleta, Harkless, and Saline Valley Formations; and Mule Spring Limestone
Phyllite, shale, and limestone (Middle Cambrian to Ordovician)
PHYLLITE, SHALE, AND LIMESTONE-Locally includes chert and quartzite. Includes Tennessee Mountain Formation of Bushnell (1967) in western Elko County, Broad Canyon sequence of Means (1962) in Lander County, and rocks originally mapped as Palmetto Formation in Toiyabe and Toquima Ranges, northern Nye County
Platy limestone and limy siltstone, chert at base (Silurian to Early Devonian)
PLATY LIMESTONE AND LIMY SILTSTONE, CHERT AT BASE-Includes units such as Roberts Mountains Formation, and Storff Formation and Chellis Limestone of Decker (1962). Locally includes rocks of Early Devonian age at top.
Quartzite and minor amounts of conglomerate, phyllitic siltstone, limestone, and dolomite (Late Proterozoic to Early Cambrian)
QUARTZITE AND MINOR AMOUNTS OF CONGLOMERATE, PHYLLITIC SILTSTONE, LIMESTONE, AND DOLOMITE-Includes Prospect Mountain Quartzite, Osgood Mountain Quartzite, and Gold Hill Formation in northern Nevada, and Stirling Quartzite, Wood Canyon Formation, and Zabriskie Quartzite in southern Nevada.
Quartzite, phyllitic siltstone, conglomerate, limestone, and dolomite (Late Proterozoic)
QUARTZITE, PHYLLITIC SILTSTONE, CONGLOMERATE, LIMESTONE, AND DOLOMITE-Includes McCoy Creek Group (excluding Stella Lake Quartzite) in east-central Nevada and Johnnie Formation in southern Nevada.
Rhyolitic flows and shallow intrusive rocks (Middle Miocene to Late Miocene)
RHYOLITIC FLOWS AND SHALLOW INTRUSIVE ROCKS
Rhyolitic flows and shallow intrusive rocks (Early Oligocene to Early Miocene)
RHYOLITIC FLOWS AND SHALLOW INTRUSIVE ROCKS
Rhyolitic flows and shallow intrusive rocks (Miocene to Quaternary)
RHYOLITIC FLOWS AND SHALLOW INTRUSIVE ROCKS
Rhyolitic flows and shallow intrusive rocks (Late Eocene to Middle Eocene)
RHYOLITIC FLOWS AND SHALLOW INTRUSIVE ROCKS
Sandstone and quartzite (Cambrian)
SANDSTONE AND QUARTZITE-Includes Tapeats Sandstone and related rocks. Rests on Precambrian metamorphic rocks.
Sandy and silty limestone, conglomerate, and siltstone (Pennsylvanian to Late Permian)
SANDY AND SILTY LIMESTONE, CONGLOMERATE, AND SILTSTONE (Upper Pennsylvanian to Upper Permian)-Includes units such as Strathearn Formation of Dott (1955) and Buckskin Mountain, Beacon Flat, and Carlin Canyon Formations of Dott (1955)
Scott Canyon Formation (Early Cambrian to Middle Cambrian)
SCOTT CANYON FORMATION (Lower or Middle Cambrian)-Chert, shale, greenstone, and sparse limestone and quartzite. Southeast Humboldt County and northwest Lander County.
Sedimentary rocks (Late Cretaceous to Oligocene)
SEDIMENTARY ROCKS-Includes Sheep Pass Formation (Eocene) and related units and unnamed tuffaceous sedimentary rocks
Shale and chert (Silurian)
SHALE AND CHERT-Includes Fourmile Canyon Formation in Eureka County and Noh Formation of Riva (1970) and unnamed rocks in Elko County.
Shale and thin-bedded or laminated limestone; also thinly interbedded limestone and chert (Middle Cambrian to Late Cambrian)
SHALE AND THIN-BEDDED OR LAMINATED LIMESTONE; ALSO THINLY INTERBEDDED LIMESTONE AND CHERT-Includes units such as Preble and Emigrant Formations
Shale, chert, and limestone (Ordovician)
SHALE, CHERT, AND LIMESTONE-Includes Aura Formation of Decker (1962) in northwest Elko County and Perkins Canyon Formation of Kay and Crawford (1964) in northern Nye County
Shale, chert, and minor amounts of quartzite, greenstone, and limestone (Ordovician)
SHALE, CHERT, AND MINOR AMOUNTS OF QUARTZITE, GREENSTONE, AND LIMESTONE-Includes units such as Vinini Formation of north-central Nevada, Palmetto Formation in southern and central parts of Esmeralda County, and Comus Formation in Humboldt County. Locally includes rocks of Silurian and Devonian age.
Shale, mudstone, siltstone, sandstone, and carbonate rock; sparse volcanic rock (Late Triassic to Early Jurassic)
SHALE, MUDSTONE, SILTSTONE, SANDSTONE, AND CARBONATE ROCK; SPARSE VOLCANIC ROCK (Upper Triassic and Lower Jurassic)-Includes Auld Lang Syne Group, Nightingale sequence of Bonham (1969), and Gabbs and Sunrise Formations
Shale, sandstone, volcanogenic clastic rocks, andesite, rhyolite, and locally thick carbonate units (Late Triassic to Early Cretaceous)
SHALE, SANDSTONE, VOLCANOGENIC CLASTIC ROCKS, ANDESITE, RHYOLITE, AND LOCALLY THICK CARBONATE UNITS-Undivided sequence locally containing recognizable equivalents of the Luning and Dunlap Formations
Shale, siliceous siltstone, chert, and minor amounts of limestone (Devonian)
SHALE, SILICEOUS SILTSTONE, CHERT, AND MINOR AMOUNTS OF LIMESTONE-Includes Cockalorum Wash Formation of northern Nye County and Woodruff Formation and unnamed rocks in Elko County
Shale, siltstone, sandstone, chert-pebble conglomerate, and limestone (Devonian to Mississippian)
SHALE, SILTSTONE, SANDSTONE, CHERT-PEBBLE CONGLOMERATE, AND LIMESTONE-Includes units such as Pilot Shale, Joana Limestone, Chainman Shale, and Diamond Peak Formation in northern and eastern Nevada and Narrow Canyon Limestone, Mercury Limestone, and Eleana Formation in southern Nevada
Siliceous and volcanic rocks (Mississippian)
SILICEOUS AND VOLCANIC ROCKS-In Humboldt County, consists of altered pillow lavas, coarse volcanic breccias, clastic limestone, and minor amounts of sandstone, shale, siliceous shale, and chert of the Goughs Canyon Formation (Lower and Upper Mississippian). In the East Range, Pershing County, consists of quartzite, conglomerate, slate, limestone, chert, and greenstone of the Inskip Formation (Mississippian?).
Siliceous and volcanic rocks (Ordovician to Devonian)
SILICEOUS AND VOLCANIC ROCKS-Chert, shale, quartzite, greenstone, and minor amounts of limestone. Includes units such as Valmy Formation of north-central Nevada and some rocks mapped as Palmetto Formation in northern part of Esmeralda County and adjacent parts of Mineral and Nye Counties. Locally includes rocks of Silurian and Devonian age.
Siltstone, sandstone, limestone, and dolomite (commonly silty or sandy) and gypsum (Early Permian)
SILTSTONE, SANDSTONE, LIMESTONE, AND DOLOMITE (COMMONLY SILTY OR SANDY), AND GYPSUM (Lower Permian)-Includes units such as Rib Hill Sandstone and Pequop Formation of Steele (1959) in Elko County, Rib Hill Sandstone and Arcturus Formation in White Pine County, Queantoweap Sandstone of NcNair (1951), Hermit Shale, and Coconino Sandstone in Clark and southern Lincoln Counties.
Silty limestone, minor amounts of shale, and some greenstone (Permian to Early Triassic)
SILTY LIMESTONE, MINOR AMOUNTS OF SHALE, AND SOME GREENSTONE-Unnamed sequence in Adobe Range, northern Elko County
Slaven Chert (Devonian)
SLAVEN CHERT-Chert and sparse limy sandstone, siltstone, and limestone. Lander County
Tuffaceous sedimentary rocks (Late Eocene to Late Miocene)
TUFFACEOUS SEDIMENTARY ROCKS-Locally includes minor amounts of tuff
Tuffaceous sedimentary rocks (Early Oligocene to Early Miocene)
TUFFACEOUS SEDIMENTARY ROCKS-Locally includes minor amounts of tuff
Volcanic flows and flow breccias, chiefly of andesitic composition, tuffs, sparse sandstone and graywacke (Permian to Jurassic)
VOLCANIC FLOWS AND FLOW BRECCIAS, CHIEFLY OF ANDESITIC COMPOSITION, TUFFS, SPARSE SANDSTONE AND GRAYWACKE-Includes Happy Creek Volcanic Series and related rocks in Humboldt County and similar rocks in Washoe and Pershing Counties; includes andesite breccias and volcanogenic sedimentary rocks in Mineral County
Volcanic sandstone, felsic ash-flow tuffs, rhyolite, and rhyodacite flows (Middle Jurassic to Early Cretaceous)
VOLCANIC SANDSTONE, FELSIC ASH-FLOW TUFFS, RHYOLITE, AND RHYODACITE FLOWS (Upper? Jurassic)-Pony Trail Group of Cortez Mountains, Eureka County
Volcanogenic sedimentary rocks, tuff, andesite and felsitic flows, and carbonate rocks (Permian to Jurassic (?))
VOLCANOGENIC SEDIMENTARY ROCKS, TUFF, ANDESITIC AND FELSITIC FLOWS, AND CARBONATE ROCKS-Age uncertain. Mineral, Esmeralda, and Northwest Nye Counties
Welded and nonwelded silicic ash-flow tuffs (Early Oligocene to Early Miocene)
WELDED AND NONWELDED SILICIC ASH-FLOW TUFFS-Locally includes thin units of air-fall tuff and sedimentary rock
Welded and nonwelded silicic ash-flow tuffs (Late Eocene to Middle Eocene)
WELDED AND NONWELDED SILICIC ASH-FLOW TUFFS-Locally includes thin units of air-fall tuff and sedimentary rock
Wyman Formation (Late Proterozoic)
WYMAN FORMATION-Phyllite and phyllitic siltstone and minor amounts of limestone, dolomite, and sandstone
New York
Amphibolite (Middle Proterozoic)
Amphibolite - pyroxenic amphibolite, hornblende gneiss, commonly biotitic, garnetiferous; subordinate calcsilicate rock.
Bedford Gneiss (Ordovician?)
Bedford Gneiss - biotite-quartz-plagioclase gneiss and interlayered amphibolite; in part with augen of andesine and microcline.
Beekmantown Group (Cambrian)
Beekmantown Group - Mohawk Valley: Little Falls Dolostone-chert; Hoyt Formation-limestone, dolostone, oolite. Washington county: Whitehall Formation-dolostone, limestone; Ticonderoga Dolostone-chert.
Beekmantown Group (Lower Ordovician)
Beekmantown Group - Mohawk Valley: Chuctanunda Creek Dolostone; Tribes Hill Formation-limestone, dolostaone; Gailor Dolostone. Washington County: Providence Island Dolostone; Fort Cassin Formation-limestone, dolostone; Fort Ann Formation-limestone, dolostone; Cutting Formation-dolostone, local chert, limestone at top, siltstone at base.
Beekmantown Group (in part) (Cambrian)
Beekmantown Group (in part) - In Champlain Valley: Whitehall Formation-dolostone, limestone (with Cryptozoon reefs); Ticonderoga Formation-dolostone (locally cherty), sandstone. In Vermont: Clarendon Springs Dolostone; Danby Formation-sandstone, quartzite, dolostone.
Beekmantown Group (in part) (Lower Ordovician)
Beekmantown Group (in part) - In St. Lawrence Valley: Ogdensburg Dolostone (Beauharnois Dolostone in Canada); In Champlain Valley: Providence Island Dolostone; Fort Cassin Formation-limestone, dolostone; Fort Ann Formation (Spellman of Clinton and Essex Counties)-limestone, dolostone; Cutting Formation-dolostone (locally cherty), limestone, siltstone. In Vermont: includes Bridport, Bascom, Cutting, and Shelburne carbonates.
Beers Hill, Dunn Hill, Millport, and Moreland Shales; Grimes Siltstone (Upper Devonian)
Beers Hill, Dunn Hill, Millport, and Moreland Shales; Grimes Siltstone.
Biotite and/or hornblende granite gneiss (Middle Proterozoic)
Biotite and/or hornblende granite gneiss - locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. Overprint signifies inequigranular texture or phacoidal structure. In northwest Adirondacks, grades into Yphg.
Biotite and/or hornblende granite gneiss (Middle Proterozoic)
Biotite and/or hornblende granite gneiss - locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. In northwest Adirondacks, grades into Yphg.
Biotite and/or hornblende granite gneiss (Middle Proterozoic)
Biotite and/or hornblende granite gneiss - locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. Overprint signifies inequigranular texture or phacoidal structure. In northwest Adirondacks, grades into Yphg.
Biotite and/or hornblende granite gneiss (Middle Proterozoic)
Biotite and/or hornblende granite gneiss - locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. Overprint signifies inequigranular texture or phacoidal structure. In northwest Adirondacks, grades into Yphg.
Biotite-quartz-plagioclase gneiss (Middle Proterozoic)
Biotite-quartz-plagioclase gneiss - commonly very low in biotite content, with interbedded feldspathic and biotitic quartzite and amphibolite; sillimanite and garnet common, graphite sporadic.
Biotite-quartz-plagioclase gneiss (Middle Proterozoic)
Biotite-quartz-plagioclase gneiss - with subordinate biotite granitic gneiss, amphibolite, calcsilicate rock.
Biotite-quartz-plagioclase gneiss, amphibolite, and related migmatite (Middle Proterozoic)
Biotite-quartz-plagioclase gneiss, amphibolite, and related migmatite - locally sillimanitic; commonly garnetiferous in and adjacent to Adirondack Highlands.
Biotite-quartz-plagioclase paragneiss (Middle Proterozoic)
Biotite-quartz-plagioclase paragneiss - commonly very low in biotite content, with interbedded feldspathic and biotitic quartzite and amphibolite; sillimanite and garnet common, graphite sporadic.
Biotite-quartz-plagioclase paragneiss, amphibolite, and related migmatite (Middle Proterozoic)
Biotite-quartz-plagioclase paragneiss, amphibolite, and related migmatite - locally sillimanitic; commonly garnetiferous in and adjacent to Adirondack Highlands.
Black River Group (Middle Ordovician)
Black River Group - In Black River Valley: Chaumont Limestone-locally cherty; Lowville Limestone; Pamelia Formation-dolostone, shale, arkose. In Champlain Valley: Amsterdam, Isle La Motte, and Lowville Limestones: Pamelia Dolostone.
Black River Group (Middle Ordovician)
Black River Group - Chaumont Limestone-chert; Lowville Limestone; Pamelia Dolostone.
Bloomsburg Formation (Upper Silurian)
Bloomsburg Formation - shale, sandstone; Guymard Quartzite; Otisville Shale; Shawangunk Conglomerate-sandstone, conglomerate.
Briarcliff Dolostone and Pine Plains Formation (Cambrian)
Briarcliff Dolostone and Pine Plains Formation - Briarcliff -l ocally cherty; Pines Plains - dolostone, shale, oolite.
Brunswick Formation (Upper Triassic)
Brunswick Formation - sandstone, siltstone and mudstone.
Brunswick Formation (Upper Triassic)
Brunswick Formation - mudstone, sandstone and arkose.
Brunswick Formation, undivided (Upper Triassic)
Brunswick Formation, undivided - includes the units: TRbg: sandstone and conglomerate; TRbs: sandstone, siltstone, mudstone; TRba: mudstone, sandstone, and arkose.
Calcitic and dolomitic marble (Middle Proterozoic)
Calcitic and dolomitic marble - variably siliceous; in part with calcsilicate rock and amphibolite.
Calcitic and dolomitic marble (Middle Proterozoic)
Calcitic and dolomitic marble - variably siliceous; in part with calcsilicate rock and amphibolite.
Calcitic and dolomitic marble (Middle Proterozoic)
Calcitic and dolomitic marble - predominantly; variably siliceous; in part with calcsilicate rock and amphibolite.
Camillus and Syracuse Formations (Upper Silurian)
Camillus and Syracuse Formations - shale, dolostone, gypsum, salt.
Camillus, Syracuse, and Vernon Formations (Upper Silurian)
Camillus, Syracuse, and Vernon Formations - shale, dolostone, salt, and gypsum.
Cashaqua and Middlesex Shales (Upper Devonian)
Cashaqua and Middlesex Shales.
Charnockite, granitic and quartz syenite gneiss (Middle Proterozoic)
Charnockite, granitic and quartz syenite gneiss - variably leucocratic, containing varying amounts of hornblende, pyroxenes, biotite; may contain interlayered amphibolite, metasedimentary gneiss, migmatite. Overprint signifies inequigranular texture or phacoidal structure.
Charnockite, granitic and quartz syenite gneiss (Middle Proterozoic)
Charnockite, granitic and quartz syenite gneiss - variably leucocratic, containing varying amounts of hornblende, pyroxenes, biotite; may contain interlayered amphibolite, metasedimentary gneiss, migmatite. Overprint signifies inequigranular texture or phacoidal structure.
Charnockite, mangerite, pyroxene-quartz syenite gneiss (Middle Proterozoic)
Charnockite, mangerite, pyroxene-quartz syenite gneiss - overprint signifies inequigranular texture.
Charnockite, mangerite, pyroxene-quartz syenite gneiss (Middle Proterozoic)
Charnockite, mangerite, pyroxene-quartz syenite gneiss - overprint signifies inequigranular texture.
Cheshire Quartzite and Dalton Formation (Cambrian)
Cheshire Quartzite and Dalton Formation
Clinton Group (Lower Silurian)
Clinton Group - Herkimer Sandstone; Kirkland Hematite; Willowvale Shale; Westmoreland Hematite; Sauquoit Formation-sandstone, shale; Oneida Conglomerate.
Clinton Group (Lower Silurian)
Decew Dolostone, Rochester Shale, Irondequoit and Merriton Limestones.
Clinton Group (Silurian)
Clinton Group - Herkimer Sandstone including Joslin Hill and Jordanville Members; Kirkland Hematite; Willowvale Shale; Westmoreland Hematite; Sauquoit Formation-sandstone, shale; Otsquago Sandstone; Oneida Conglomerate.
Cobleskill Limestone (Upper Silurian)
Cobleskill Limestone; Bertie, Camillus, and Syracuse Formations - shale, dolostone; Brayman Shale.
Cobleskill Limestone (Upper Silurian)
Cobleskill Limestone - Bertie and Camillus Formations-dolostone, shale.
Conneaut Group, undivided (Upper Devonian)
Conneaut Group, undivided - In west: Ellicott and Dexterville Formations-shale, siltstone. In east: Germania Formation-shale, sandstone; Whitesville Formation-shale, sandstone; Hinsdale Sandstone; Wellsville Formation-shale, sandstone; Cuba Sandstone.
Connoquenessing and Sharon Formations (Lower Pennsylvanian)
Connoquenessing and Sharon Formations - sandstone, shale; Sharon Formation-shale, sandstone, conglomerate; Olean Conglomerate 50-100 ft. (15-30 m).
Copake and Halcyon Lake Formations, Rochdale Limestone (Lower Ordovician)
Copake and Halcyon Lake Formations, Rochdale Limestone - Columbia County: Copake Formation-limestone, dolostone; Halcyon Lake Formation-chert, calc-dolostone.
Copake and Rochdale Formations (Lower Ordovician)
Copake and Rochdale Formations - Copake Formation-limestone, dolostone, siltstone; Rochdale Formation-limestone, dolostone; Halcyon Lake Dolostone-locally cherty.
Cuyahoga and Knapp Formations (Lower Mississippian)
Cuyahoga and Knapp Formations - Cuyahoga Formation-shale, sandstone; Corry Sandstone; Knapp Formation-shale, conglomerate 60-100 ft. (20-30 m).
Decew Dolostone and Rochester Shale (Lower Silurian)
Decew Dolostone and Rochester Shale
Decew Dolostone and Rochester Shale (Lower Silurian)
Decew Dolostone and Rochester Shale
Dolomitic and calcitic marbles interlayered with significant amounts of calcsilicate rock (Middle Proterozoic)
Dolomitic and calcitic marbles interlayered with significant amounts of calcsilicate rock - metasedimentary amphibolite, pyroxene granulite, and various gneisses; includes interlayered diopsidic and tremolitic marble and quartzite, and talc-tremolite rock (mined in Balmat-Edwards belt, northwest Adirondacks).
Elizaville Formation (Cambrian - Ordovician)
Elizaville Formation - shale, argillite, quartzite.
Elizaville Formation (Cambrian - Ordovician)
Elizaville Formation - shale, argillite, quartzite.
"Enfield" and Kattel Formations (Upper Devonian)
"Enfield" and Kattel Formations - shale, siltstone, sandstone.
Fordham Gneiss (A member) (Precambrian - Middle Proterozoic )
Fordham Gneiss (A member) - fa: garnet-biotite-quartz-plagioclase gneiss, amphibolite, biotite-hornblende-quartz-plagioclase gneiss, quartz-feldspar granulite.
Fordham Gneiss (C and D member) (Precambrian - Middle Proterozoic )
Fordham Gneiss (C and D member) - fc: biotite-hornblende-quartz-plagioclase gneiss, quartz-feldspar lenses, amphibolite, biotite and/or hornblende-quartz-feldspar gneiss; fd: sillimanite-garnet schistose gneiss, quartzite.
Fordham Gneiss, undivided (Precambrian - Middle Proterozoic )
Fordham Gneiss, undivided - fe: garnet-biotite-quartz-plagioclase gneiss, and amphibolite; fd: sillimanite-garnet schistose gneiss, quartzite; fc: biotite- hornblende-quartz-plagioclase gneiss, quartz-feldspar lenses, amphibolite, biotite and/or hornblende-quartz-feldspar gneiss; fb: amphibolite, biotite and/or hornblende-garnet-quartz-plagioclase gneiss; fa: garnet-biotite-quartz-plagioclase gneiss, amphibolite, biotite-hornblende-quartz-plagioclase gneiss, quartz-feldspar granulite.
Gabbro or norite to hornblende diorite (Upper Ordovician)
Gabbro or norite to hornblende diorite - rock complex with minor pyroxenite; Croton Falls and Peach Lake complexes in New York, and Mt. Prospect Complex in Connecticut.
Garnet-bearing gneiss and interlayered quartzite (Middle Proterozoic)
Garnet-bearing gneiss and interlayered quartzite - contains varying amounts of biotite, garnet, sillimanite; minor marble, amphibolite, rusty paragneiss.
Garnet-biotite-quartz-feldspar gneiss (Middle Proterozoic)
Garnet-biotite-quartz-feldspar gneiss - quartzite, quartz-feldspar gneiss, calcsilicate rock.
Genesee Group (Upper Devonian)
Genesee Group - West River Shale; Genundewa Limestone; Penn Yan and Geneseo Shales; North Evans Limestone.
Genesee Group (Upper Devonian)
Genesee Group - West River Shale; Genundewa Limestone; Penn Yan and Geneseo Shales; all except Geneseo replaced eastwardly by Ithaca Formation-shale, siltstone and Sherburne Siltstone.
Germantown Formation (Cambrian)
Germantown Formation - south of Troy; shale, conglomerate, limestone.
Germantown Formation (Cambrian)
Germantown Formation - shale, limestone, conglomerate.
Glenerie Formation (Lower Devonian)
Glenerie Formation - limestone, chert.
Glenerie Formation (Lower Devonian)
Glenerie Formation - limestone, chert; Port Jervis Formation (near Port Jervis only)-shale, limestone, chert.
Greenstones and tuffs and/or basalt (Cambrian?)
Greenstones and tuffs and/or basalt
Interlayered gabbroic or noritic metanorthosite (Middle Proterozoic)
Interlayered gabbroic or noritic metanorthosite - mangerite or charnockite, and the Yach lithology.
Inwood Marble (Early Cambrian - Lower Ordovician)
Inwood Marble - dolomite marble, calc-schist, granulite, and quartzite, overlain by calcite marble; grades into underlying patchy Lowerre Quartzite of Early Cambrian age.
Irondequoit Limestone thru Kodak Sandstone (Lower Silurian)
Irondequoit Limestone thru Kodak Sandstone - includes: Irondequoit Limestone, Williamson Shale; Wolcott Furnace Hematite; Wolcott Limestone; Sodus Shale; Bear Creek Shale; Wallington Limestone; Furnaceville Hematite; Maplewood Shale; Kodak Sandstone.
Irondequoit Limestone thru Kodak Sandstone (Lower Silurian)
Irondequoit Limestone thru Kodak Sandstone - includes: Irondequoit Limestone, Rockway Dolostone, Hickory Corners Limestone, Neahga Shale, and Kodak Sandstone.
Lamprophyre, diabase, and albite-basalt dikes (Jurassic - Lower Cretaceous)
Lamprophyre, diabase, and albite-basalt dikes - not shown in Proterozoic terrane.
Lamprophyre, trachyte, and rhyolite dikes (Jurassic - Lower Cretaceous)
Lamprophyre, trachyte, and rhyolite dikes - not shown in Proterozoic terrane.
Leucogranitic (alaskitic) gneiss (Middle Proterozoic)
Leucogranitic (alaskitic) gneiss - sodic plagioclase ranges from generally subordinate to locally dominant; locally with biotite, hornblende, pyroxene, garnet, sillimanite, disseminated magnetite; commonly contains metasedimentary layers, amphibolite, migmatite; plagioclase-rich variety is host to magnetite ore bodies in eastern Adirondacks.
Leucogranitic gneiss (Middle Proterozoic)
Leucogranitic gneiss - sodic plagioclase ranges from generally subordinate to locally dominant; locally with biotite, hornblende, pyroxene, garnet, sillimanite, disseminated magnetite; commonly contains metasedimentary layers, amphibolite, migmatite; plagioclase-rich variety is host to magnetite ore bodies in eastern Adirondacks.
Lower Walton Formation (Upper Devonian)
Lower Walton Formation - shale, sandstone, conglomerate.
Lower Walton Formation (Upper Devonian)
Lower Walton Formation - shale, sandstone, conglomerate.
Ludlowville Formation (Middle Devonian)
Ludlowville Formation - Deep Run Shale, Tichenor Limestone, Wanakah and Ledyard Shales, Centerfield Limestone Members.
Ludlowville Formation (Middle Devonian)
Ludlowville Formation - In west: Deep Run Shale, Tichenor Limestone, Wanakah and Ledyard Shales, Centerfield Limestone Members. In east: King Ferry Shale and other members, Stone Mill Sandstone Member.
Machias Formation (Upper Devonian)
Machias Formation - shale, siltstone; Rushford Sandstone; Caneadea, Canisteo, and Hume Shales; Canaseraga Sandstone; South Wales and Dunkirk Shales.
Machias Formation (Upper Devonian)
Machias Formation - shale, siltstone; Rushford Sandstone; Caneadea, Canisteo, and Hume Shales; Canaseraga Sandstone; South Wales and Dunkirk Shales; In Pennsylvania: Towanda Formation-shale, sandstone.
Manhattan Formation (A Member) (Middle Ordovician)
Manhattan Formation (A member) - sillimanite-garnet-muscovite-biotite-quartz- plagioclase schists; calcite marble and calcsilicate rock at base.
Manhattan Formation, undivided (Ordovician?)
Manhattan Formation, undivided - pelitic schists, amphibolite; Units ?Omb, ?Omc, and ?Omd may be Cambrian eugeosynclinal rocks thrust upon Oma; ?Omd - sillimanite-garnet-muscovite-biotite-plagioclase-quartz gneiss; ?Omc - sillimanite-garnet-muscovite-biotite-quartz-plagioclase schistose gneiss, sillimanite nodules, local quartz-rich layers; ?Omb - discontinous unit of amphibolite and ?Omc-type schist.
Marcellus Formation (Middle Devonian)
Marcellus Formation - Pecksport, Solsville, Otsego, and Chittenango shale and sandstone Members, Cherry Valley Limestone, and Union Springs Shale Members.
Medina Group (Lower Silurian)
Medina Group - Grimsby Formation-sandstone, shale.
Mettawee Slate (Cambrian ?)
Mettawee Slate - north of 43 degrees includes Castleton (North Brittain) Conglomerate. Mudd Pond Quartzite, Zion Hill Quartzite, and Bomoseen Graywacke Members.
Mettawee Slate (Cambrian?)
Mettawee Slate (Bull in Vermont) - includes Castleton (North Brittain) Conglomerate. Mudd Pond Quartzite, Zion Hill Quartzite, and Bomoseen Graywacke Members.
Monmouth Group, Matawan Group and Magothy Formation (Upper Cretaceous)
Monmouth Group, Matawan Group and Magothy Formation - silty clay, glauconitic sandy clay, sand, gravel.
Mount Merino and Indian River Formations (Ordovician)
Mount Merino and Indian River Formations - shale, slate, cherts.
Mount Merino and Indian River Formations (Ordovician)
Mount Merino and Indian River Formations - shale, argillite, chert.
Mount Merino and Indian River Formations (Ordovician)
Mount Merino and Indian River Formations - shale, slate, cherts.
Nassau Formation (Cambrian ?)
Nassau Formation - south of 43 degrees; slate, shale, thin quartzite, includes Stuyvesant Conglomerate, Diamond Rock Quartzite, Curtis Mountain Quartzite, and Bomoseen Graywacke Members.
Normanskill Formation (Middle Ordovician)
Normanskill Formation - shale, argillite, siltstone.
Normanskill Shale (Middle Ordovician)
Normanskill Shale - minor mudstone, sandstone.
Nunda Formation, West Hill Formation (Upper Devonian)
Nunda Formation, West Hill Formation - Nunda: sandstone, shale; West Hill: shale, siltstone; Corning Shale.
Oneonta Formation (Middle - Upper Devonian)
Oneonta Formation - shale, sandstone, conglomerate.
Onondaga and Bois Blanc Limestones (Middle Devonian)
Onondaga and Bois Blanc Limestones - In New York: Onondaga Limestone-Seneca, Morehouse (cherty), and Clarence Limestone Members, Edgecliff cherty Limestone Member, local coral bioherms; Bois Blanc Limestone-sandy, thin, discontinous. In Ontario: Dundee Limestone; Lucas Formation-dolostone, limestone (Anderdon); Amherstburg Formation-limestone, dolostone, sandstone (Sylvania); Bois Blanc Formation-dolostone, limestone, sandstone (Springvale).
Onondaga Limestone (Lower to Middle Devonian)
Onondaga Limestone - Seneca, Morehouse (cherty), and Nedrow Limestone Members, Edgecliff cherty Limestone Member, local bioherms, Buttermilk Falls Limestone Member; Schoharie Formation-shale, limestone; Carlisle Center Siltstone; Esopus Shale.
Onondaga Limestone (Lower to Middle Devonian)
Onondaga Limestone - Schoharie Formation-shale, limestone; Carlisle Center Siltstone; Esopus Shale.
Oswayo and Venango Formations (Upper Devonian)
Oswayo and Venango Formations - shale, siltstone, sandstone; replaced eastwardly by Cattaraugus Formation-shale, sandstone, conglomerate.
Panther Mountain Formation (Middle Devonian)
Panther Mountain Formation - shale, siltstone, sandstone.
Panther Mountain Form