U.S. Geological Survey 2002 version 1.0 tabular digital data Zartman, Robert. E. Bush, Charles. A. Abston Carl 1995 U.S. Geological Survey Digital Data Series DDS-14 http://edc.usgs.gov/glis/hyper/guide/ngdb This data set, dds14kar, is a subset of the National Geochronological Data Base (NGDB), as published in 1995. It shows the distribution of published K/Ar and Ar/Ar age determinations in the United States. Sample location, rock description, analytical data, age, interpretation, and literature citation is given for each record. This GIS representation of the data set facilitates the presentation and analysis of earth-science data. 1995 publication date Complete None planned 177.5 -67.1 71.0 25.3 None K/Ar geochronology Ar/Ar geochronology radiometric age geochronology None US United States of America None The U.S. Geological Survey makes no warranties related to the accuracy of the data and users are required to determine the usability for any particular purpose. U.S. Geological Survey Nora Shew mailing and physical address

4200 University Drive

Anchorage AK 99508-4667 U.S.A. 907-561-1181 nshew@usgs.gov The National Geochronological data base is maintained by the U.S. Geological Survey. It was published by Robert E. Zartman, Charles A. Bush, and Carl Abston in 1995. The K/Ar and Ar/Ar portion of the data base was prepared for by Nora Shew and Tom Kress. The radiometric ages are given in m.y., millions of years. The analytical error, also given in m.y., is listed for most ages. The numerical precision was not maintained during the data conversion and the user should be aware that more precision may be indicated than is real. Users should use this data set to learn about existing data, then research the original references to gain more information about the sample, analysis, and interpretation. This is a point data set, where each point represents a published analytical age determination. If an age is published in multiple references, it is represented as a single point and only a single reference is cited. This data set contains a subset of the National Geochronological data base, NGDB. Data for samples dated by a potassium-argon dating method and include location information are given here. The data set does not include the following dating methods: fission track, lead alpha, rubidium-strontium, samarium-neodymium, or uranium-thorium-lead. In addition, many fields associated with the K/Ar and Ar/Ar records were not included. Some of the missing fields are: analysis number, lab number, suite number, mineral code, county, quadrangle, scale, source, geo unit, petrographic code, lab code, and lexicon age. The precision of the latitude and longitude values was not maintained during the data conversion and the user should be aware that more precision may be indicated than is real. The text field 'Precision' describes the positional accuracy of each point. Zartman, Robert E. Bush, Charles A. Abston, Carl 1995 tabular digital data U.S. Geological Survey Digital Data Series DDS-14A CD-ROM 1995 publication date DDS-14A The entire data set was obtained from DDS-14A. The National Geochronologic data base (NGDB) is stored in a relational data base program. DDS-14A published the data as a relational data base and separate ASCII format. The comma seperated value files were imported into database software, Access, where the table relationships were re-built. It was necessary to edit some records in order for the data base to be re-built. The actual data values were not changed. Once the Access data base was completed, select fields were used to build a DBF file. Using ArcView a shapefile was produced called dds14_k_ar_age.shp 2001 Point .002 .002 Decimal degrees points Rock or mineral sample dated by K/Ar geochronology Recno (Record Number) Unique NGDB identifier for sample. Multiple analyses on a single sample have the same Record Number. 3 18332 Rockname (Rock) Rock type from which the dating sample is from descriptive text of mixed case Mineral Mineral or phase dated descriptive text of mixed case Age Age of sample in millions of years (m.y.) -0.09 6883 m.y. (million years) Error Analytical error of calculated age 0 940 m.y. (million years) Analysisty Method of K/Ar dating (no value) 37Ar-41Ar total fusion 39Ar-40Ar incremental (plateau) 39Ar-40Ar total fusion 40Ar-40K isochron 40Ar/36Ar-40K/36Ar isochron Conventional K-Ar Conventional Rb-Sr (assumed initial 87Sr/86Sr) Agecomment Informative text about the estimated age or the material analyzed (no value) age meaning uncertain (analysis questionable) age meaning uncertain (geologic factors) age not evaluated age of intrusion age of later metamorphism age of metamorphic crystallization age of sedimentation age of uplift and cooling age of volcanism age reset by thermal event anomalous initial isotopic composition, age questionable initial age disturbed by later metamorphism initial age disturbed by weathering maximum age of intrusion maximum age of metamorphic crystallization maximum age of volcanism may denote delayed cooling minimum age of intrusion minimum age of metamorphic crystallization minimum age of mineralization minimum age of volcanism sample contains excess radiogenic argon, age is too old sample contains inherited material, age is too old K2Opct percent K20 0 64 percent Ar40mol radiogenic 40Ar expressed as mol/gm scaled by 1.0E-10 0.000000 2453.000000 mol/gm Arradpct (Arrad%) Percent radiogenic Ar 0 100 percent Deccon (Decay constant) Potassium decay contants used in age calculation text Latitude latitude in decimal degrees 26.67 71.0 degree Latdir Direction of latitude N North Longitude longitude in decimal degrees -67.1 177.5 degree Longdir Direction of Longitude E East W West St (State) Two letter abbreviation for State sample was collected from Two-letter abbreviations for US states USPS Precision Description of location precision descriptive text Refcode NGDB coded value linking radiometric date with published reference Reference Reference which is the source of the analytical information bibliographic citation U.S. Geological Survey Tom Kress mailing address

12201 Sunrise Valley Drive MS954

Reston VA 20192 USA 703-648-6328 thkress@usgs.gov dds14k_ar_age.shp The U.S. Geological Survey (USGS) provides this point data "as is." The USGS makes no guarantee or warranty concerning the accuracy of information contained in the dataset. Further, the USGS makes no warranties, either expressed or implied, as to any other matter whatsoever, including, without limitation, the condition of the product, or its fitness for any particular purpose. The burden for determining fitness for use lies entirely with the user. Although this data has been processed successfully on computers at the USGS, no warranty, express or implied, is made by the USGS regarding the use of this data on any other system, nor does the fact of distribuiton constitute or imply any such warranty. ESRI shapefile 1.0 Sample locations and age information unzip 1 megabyte http://tin.er.usgs.gov/karage/karage.zip none 20020123 20030303 U.S. Geological Survey Nora Shew mailing and physical address

4200 University Drive

Anchorage AK 99508-4667 USA 907-561-1181 nshew@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998