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Geologic units in Jefferson county, West Virginia
[Additional scientific data in this geographic area]
- Trenton Group and Black River Group, undivided (Ordovician) at surface, covers 0.1 % of this area
Trenton Group and Black River Group, undivided - Trenton Group: dark, crystalline, nodular, and argillaceous limestones, with some metabentonite streaks. Includes the Nealmont, Oranda, Edinburg, and the upper part of the Chambersburg Limestones of northeastern West Virginia; also the Moccasin and Eggleston Formation of Mercer and Monroe Counties. Black River Group: predominantly gray aphanitic limestones, with many bioclastic streaks; siliceous in the lower part.
- Ordovician, middle calcareous units (Ordovician) at surface, covers 3 % of this area
Ordovician - middle calcareous units.
- Martinsburg Formation (Ordovician) at surface, covers < 0.1 % of this area
Martinsburg Formation - predominantly gray to dark shale, yellowish in the upper portion. Contains scattered thin limestone and sandstone interbeds, particularly in the lower portion. The upper portion constitutes the Reedsville Shale.
- Stonehenge Limestone (Ordovician) at surface, covers 10 % of this area
Stonehenge Limestone - gray, thin-bedded to massive, fossiliferous limestone, largely mechanically deposited, with small black chert nodules and beds of "edgewise" conglomerate. The highly resistant Stoufferstown Limestone member is found at the base.
- Rockdale Run Formation (Ordovician) at surface, covers 7 % of this area
Rockdale Run Formation - bluish to light gray and brown, thick-bedded dolomite and limestone, containing gray chert and zones of Cryptozoa and Lecanospira.
- Pinesburg Station Dolomite (Ordovician) at surface, covers 1.0 % of this area
Pinesburg Station Dolomite - fine- to medium-crystalline, brown to light gray dolomite, containing nodular chert.
- Waynesboro Formation (Cambrian) at surface, covers 6 % of this area
Waynesboro Formation - variegated shale and sandstone, commonly red or brown. Middle zone contains much dolomite and limestone. Contains the Olenellus fauna of Early Cambrian age, although its upper portion may be of Middle Cambrian age.
- Weverton-Loudoun Formation (Cambrian) at surface, covers 2 % of this area
Weverton-Loudoun Formation (Chilhowee Group) - tough quartzitic sandstones, conglomerates, and shale.
- Tomstown Dolomite (Cambrian) at surface, covers 6 % of this area
Tomstown Dolomite - thick-bedded, blue-gray, aphanitic, saccharoidal, and splintery dolomite, weathering coffee-brown; some siliceous limestone and black chert. Contains commercial beds of white, pure, low-silica dolomite.
- Catoctin Formation (Cambrian/Precambrian) at surface, covers < 0.1 % of this area
Catoctin Formation - predominantly a greenstone. Basic lava flows, schist and gneiss, containing chlorite, plagioclase, amphibolite, and epidote. Includes minor quantities of arkose and thin clastics. Western subsurface extension presently unknown.
- Harpers Formation (Cambrian) at surface, covers 6 % of this area
Harpers Formation (Chilhowee Group) - greenish-gray phyllite, with interbeds of fine-grained quartzite.
- Elbrook Formation (Cambrian) at surface, covers 19 % of this area
Elbrook Formation - thin-bedded blue-gray argillaceous limestone and platy shale, with some siliceous limestone and minor dolomite.
- Conococheague Formation (Cambrian) at surface, covers 0.3 % of this area
Conococheague Formation - predominantly algal and mechanically deposited limestone, with interbeds of aphanitic limestone and dolomite. Contains siliceous and dolomitic laminations. Resistant sandy Big Spring Station Member near the base.
- Antietam Formation (Cambrian) at surface, covers 3 % of this area
Antietam Formation (Chilhowee Group) - gray to white quartzite, sandstone and quartz-schist; thick-bedded, and resistant; contains Scolithus.
- Chilhowee Group; Weverton Formation (Late Precambrian - Cambrian) at surface, covers < 0.1 % of this area
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.
- Chilhowee Group; Harpers Formation (Cambrian) at surface, covers < 0.1 % of this area
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.
- Tomstown Dolomite (Cambrian) at surface, covers < 0.1 % of this area
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.
- Elbrook Limestone (Cambrian) at surface, covers < 0.1 % of this area
Elbrook Limestone - Light blue, laminated, argillaceous limestone and calcareous shale; some dolomite; thickness 1,400 to possibly 3,000 feet.