A partial compilation and database of 40Ar-39Ar and K-Ar geochronologic data and sample locations in Arizona and southeastern-most California

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Author
Spencer, J. E.
Ferguson, C. A.
Richard, S. M.
McIntosh, W. C.
Peters, L.
Issue Date
2017
Keywords
Arizona
GEOCHRONOLOGY
K-Ar
Ar-Ar

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Citation
Spencer, J. E., Ferguson, C. A., Richard, S. M., McIntosh, W. C., and Peters, L., 2017, A partial compilation and database of 40Ar-39Ar and K-Ar geochronologic data and sample locations in Arizona and southeastern-most California: Arizona Geological Survey Digital Information (DI)-48, 6 p. text, with Excel Workbook, Access database table, and analytical data.
Publisher
Arizona Geological Survey (Tucson, AZ)
Description
During 1993-2017, the Arizona Geological Survey conducted field investigations in Arizona as part of the jointly Federal-State funded STATEMAP program, which is a component of the National Geologic Mapping Act of 1992. During these investigations, many samples were collected for 40Ar/39Ar and K-Ar geochronologic analysis, with analyses funded by various STATEMAP awards to the Arizona Geological Survey. Most of these samples were analyzed at the New Mexico Geochronology Research Laboratory which specializes in high-precision 40Ar/39Ar geochronologic analysis of sanidine from volcanic rocks. Numerous analyses have also been produced by other laboratories over the past 30 years related to various geologic field studies. This compilation, represented primarily by an Excel table and a derived table in Microsoft Access, includes analyses from studies related to STATEMAP and from miscellaneous other studies conducted over the past decades. Note also that a data-reporting publication or data file is listed for each sample in the "Source" column in the primary Excel table. Analytical data, where not previously released through Arizona Geological Survey publications, are included for some samples in data files that are part of this Digital Information Series publication (Fig. 1). Samples without accurate sample locations are not included in the primary Excel table and Access table, but are included in an additional Excel worksheet. This publication is intended for use by those engaged in geologic investigations where such data would be useful. Special care was taken in this report to determine exact sample locations. Before about year 2000, samples were typically located by plotting locations on topographic base maps while at the sample field sites. After that time, sample locations were typically recorded with a portable GPS unit in NAD27 UTM coordinates in meters. All sample locations, regardless of original sample-location method, were used to identify latitude and longitude coordinates in decimal degrees. If UTM coordinates were known, coordinate conversion was done with a U.S. National Geodetic Survey online site that would transform as many as 99 pairs of coordinates at a time (https://beta.nge.noaa.gov/gtkweb/ - note that reloading the site after a non-responsive or erroneous run was commonly necessary and led to initial inference of website malfunction). If GPS measurements were unavailable, the sample location was identified on the original field map sheet or a copy, and a USGS web site (https://viewer.nationalmap.gov/basic/#productSearch) was used to determine lat-lon. This was done by finding the same location on the digital online topographic map, placing the tip of the computer cursor arrow on that spot, and recording the lat-lon coordinates of the cursor as shown on the web page (this process was expedited by use of two computers). The positional uncertainty introduced by this method is estimated at 10-50 meters, depending on the particular site and the level of detail of represented geographic features. For example, samples collected from the sharp corner of a stream bed represented on both maps could be much more accurately located than one from a broad, even slope.
URI
http://hdl.handle.net/10150/668352
Additional Links
https://library.azgs.arizona.edu/
Language
en
Series/Report no.
DI-48
Rights
Arizona Geological Survey. All rights reserved.
Collection Information
Documents in the AZGS Documents Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu.
North Bounding Coordinate
37.0039
South Bounding Coordinate
31.332406
West Bounding Coordinate
-114.812834
East Bounding Coordinate
-109.044839
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