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Geology & Geochronology of four 7.5' quadrangles straddling the southern border of AZ - CA

The AZGS just released a contributed report by Carl Jacobson (Dept. Geological and Atmospheric Science at Iowa State University and Dept. of Earth and Space Sciences, West Chester University) and others focusing on geologic mapping and geochronology for four map quadrangles straddling the southern border of Arizona and California.

The 37-page report includes 12 figures, 3 tables, a selective bibliography of ore-related deposits, and a GIS database. This reports builds on geologic mapping in the 1980s and early 1990s by authors D.R. Sherrod, R.M. Tosdal, and G.B. Haxel. Read or download here:

From the Introduction; “This report accompanies a digital geologic map of the Picacho, Picacho SW, Picacho NW, and Hidden Valley 7.5-minute quadrangles — the four quadrants of the Picacho 15-minute quadrangle. The map area is located within the central and southern Trigo Mountains, Arizona, and southeastern Chocolate Mountains, California and is dominated by stratigraphically and structurally complex Mesozoic and Cenozoic rocks relevant to understanding the geologic evolution of the U.S. Southwest more broadly. The report provides descriptions of the geologic map units, their environments of formation, age constraints, deformational history, and regional correlations. It also includes a brief summary of metallic ore deposits within the map area, as well as a selective bibliography of publications on ore deposits in and adjacent to the map area (Appendix 1)”.

Geochron map
Location of geochronology samples. Geologic base from Plate 1. Map numbers correspond to those in the left column of Table 1. 

Cover Image: Quechan volcanic and subvolcanic rocks (late/upper Oligocene), the single most widespread unit in the map area. Gavilan Wash, California. Trigo Mountains, Arizona form right skyline.

Citation: Jacobson, C.E., Sherrod, D.R., Tosdal, R.M., Lishansky, R., Beard, L.S., Haxel, G.B., Harding, C., Grove, M.J., and Tian, B., 2022, Geologic Map of the Picacho, Picacho NW, Picacho SW, and Hidden Valley 7.5-Minute Quadrangles, Arizona and California: Arizona Geological Survey Contributed Report CR-22-C, 33 p., map scale 1:50,000, with GIS database.