A partial compilation and database of 40Ar-39Ar and K-Ar geochronologic data and sample locations in Arizona and southeastern-most California Jon E. Spencer1, Charles A. Ferguson1, Stephen M. Richard1 William C. McIntosh2, Lisa Peters2 1Arizona Geological Survey, 2New Mexico Bureau of Geology & Mineral Resources Volcanics exposed south of Ibex Peak, Plomosa Mtns., La Paz County, Arizona DIGITAL INFORMATION DI-48 July 2017 Arizona Geological Survey azgs.arizona.edu | repository.azgs.az.gov Arizona Geological Survey Philip A. Pearthree, Director Manuscript approved for publication in July 2017 Printed by the Arizona Geological Survey All rights reserved For an electronic copy of this publication: www.repository.azgs.az.gov For information on the mission, objectives or geologic products of the Arizona Geological Survey visit azgs.arizona.edu This publication was prepared by a department of the University of Arizona. The Univer- sity of Arizona, or any department thereof, or any of their employees, makes no warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report. Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the University of Arizona ___________________________ Recommended 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. Introduction 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. 1 Fig. 1. Supplemental data files that accompany this report and are listed in its primary Excel table. The lat-lon coordinates given in the primary table were not plotted to determine if their locations were consistent with reported rock units at the site. Future improvement of this database would benefit from evaluation of positional accuracy. Note: Publication includes: This text, Excel Workbook, and supplemental data file Partial list of Arizona geochronology publications Anderson, R.E., Longwell, C. R., Armstrong, R. L., and Marvin, R. F., 1972, Significance of K-Ar ages of Tertiary rocks from the Lake Mead region, Nevada-Arizona: Geological Society of America Bulletin, v. 83, p. 273- 288. Banks, N.G., McKee, E.H., Keith, S.B., Shafiqullah, M., and Damon, P.E., 1978, Radiometric and chemical data for rocks of the Tortolita Mountains 15' quadrangle, Pinal County, Arizona: Isochron/West, no. 22, p. 17-22. Bikerman, M., and Damon, P.E., 1966, K-Ar chronology of the Tucson Mountains, Pima County, Arizona: Geological Society of America, v. 77, p. 1224-1234. Creasey, S.C., 1978, Analytical data for K-Ar ages for the Mineral Mountain 7 1/2-minute quadrangle, in Theodore, T.G., Keith, W.J., Till, A.B., and Peterson, J.A, Preliminary geologic map of the Mineral Mountain 7 1/2-minute quadrangle, Arizona: U.S. Geological Survey Open-File Report 78-0468, 1 sheet, scale 1:24,000. Dalrymple, G. B., 1979, Critical tables for conversion of K-Ar ages from old to new constants: Geology, v. 7, p. 558-560. 2 Damon, P.E., and Shafiqullah, M., 2006, K-Ar dates of fault rocks along the Catalina detachment fault, Tanque Verde Ridge, Rincon Mountains, Arizona: Arizona Geological Survey, Contributed Report CR-06-A, 18 p. Damon, P.E., and Spencer, J.E., 2001, K-Ar geochronologic survey of the Hopi Buttes volcanic field, in Young, R.A., and Spamer, E.E., eds., The Colorado River: Origin and evolution: Grand Canyon, Arizona, Grand Canyon Association Monograph 12, p. 53-56. Damon, P.E., Shafiqullah, M., Harris, R.C., and Spencer, J.E., 1996, Compilation of unpublished K-Ar dates from the University of Arizona Laboratory of Isotope Geochemistry, 1971-1991, (updated April, 1997): Arizona Geological Survey Open-File Report 96-18, 56 p. Dickinson, W.R., and Shafiqullah, M., 1989, K-Ar and F-T ages for syntectonic mid-Tertiary volcanosedimentary sequences associated with the Catalina core complex and San Pedro trough in southern Arizona: Isochron/West, n. 52, p. 15-27. Erickson, R. C., 1981, K-Ar and Rb-Sr geochronology of the Dos Cabezas Mountains, Cochise County, Arizona: Tucson, Arizona Geological Society Digest, v. 13, p. 185-193. Ferguson, C.A., Enders, M.S., Peters, Lisa, and McIntosh, W.C., 2000, Mid-Tertiary geology and geochronology of the Clifton-Morenci area, Greenlee and Graham Counties, and adjacent New Mexico: Arizona Geological Survey Open-File Report 00-07, 69 p. Feuerbach, D.L., Smith, E.I., Shafiqullah, M., and Damon, P.E., 1991, New K-Ar dates for late Miocene to early Pliocene mafic volcanic rocks in the lake Mead area, Nevada and Arizona: Isochron/West, no. 57, p. 17-20 Fornash, K.F., Patchett, P.J., Gehrels, G.E., and Spencer, J.E., 2013, Evolution of granitoids in the Catalina metamorphic core complex, southeastern Arizona: U-Pb, Nd, and Hf isotopic constraints: Contributions to Mineralogy and Petrology, v. 165, p. 1295-1310; DOI 10.1007/s00410-013-0859-4 Foster, D.A., and Spencer, J.E., 1992, Apatite and zircon fission-track dates from the northern Plomosa Mountains, La Paz County, west-central Arizona: Arizona Geological Survey Open-File Report 92-9, 11 p. Foster, D.A., Harrison, T.M., Miller, C.F., and Howard, K.A., 1990, The 40Ar/39Ar thermochronology of the eastern Mojave Desert, California, and adjacent western Arizona with implications for the evolution of metamorphic core complexes: Journal of Geophysical Research, v. 95, p. 20,005–20,024. Gray, F., and Miller, R. J., 1984, New K-Ar ages of volcanic rocks near Ajo, Pima and Maricopa Counties, southwestern Arizona: Isochron/West, no. 41, p. 3-6. Isachsen, C.E., Gehrels, G.E., Riggs, N.R.,. Spencer, J.E. Ferguson, C.A., Skotnicki, S.J. Richard, S.M., 1999, U-Pb geochronologic data from zircons from eleven granitic rocks in central and western Arizona: Arizona Geological Survey Open-File Report 99-5, 27 p. Karlstrom, K.E., Crow, R.S., Peters, L., McIntosh, W., Raucci, J., Crossey, L.J., Umhoefer, P., and Dunbar, N., 2007, 40Ar/39Ar and field studies of Quaternary basalts in Grand Canyon and model for carving Grand Canyon: Quantifying the interaction of river incision and normal faulting across the western edge of the Colorado Plateau: Geological Society of America Bulletin, v. 119, n. 11/12, p. 1283- 1312; doi: 10.1130B26154.1 Marvin, R.F., and Cole, J.C., 1978, Radiometric ages; compilation A, U.S. Geological Survey: Isochron/West, n. 22, p.