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Geologic Map and Database of the Chocolate Mountain Aerial Gunnery Range, Riverside and Imperial Counties, California

Open-File Report 2018-1191
Prepared in cooperation with the U.S. Navy and U.S. Marine Corps
By: , and 

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Abstract

The northwest-trending Chocolate Mountains are situated along the northeastern margin of the southern Salton Trough. The Chocolate Mountain Aerial Gunnery Range occupies most of the 75-km-long part of the Chocolate Mountains that lies between Salt Creek to the north and California State Highway 78 to the south. Mapping studies in the Chocolate Mountains within the gunnery range are few and this study was conducted in cooperation with the U.S. Navy (Naval Facilities Engineering Command Southwest, San Diego, California) and U.S. Marine Corps (Range Management Department, Marine Corps Air Station, Yuma, Arizona).

Crystalline basement rocks in the Chocolate Mountains range in age from early Proterozoic to middle Cenozoic. Early and middle Proterozoic metamorphosed sedimentary and plutonic rocks include sillimanite-biotite-quartz feldspar gneiss, layered biotite-quartz-feldspar gneiss, biotite-quartz-feldspar augen gneiss, and largely undeformed late Proterozoic anorthosite and syenite. These rock types, which crop out as dispersed domains in the Chocolate Mountains, are remnants—along with more extensive domains observed in the Eastern Transverse Ranges to the north and in the San Gabriel Mountains to the northwest—of an originally more continuous assemblage that has been dextrally displaced along strands of the San Andreas Fault System.

Suggested Citation

Powell, R.E., Fleck, R.J., and Cossette, P.M., 2018, Geologic map and database of the Chocolate Mountain Aerial Gunnery Range, Riverside and Imperial Counties, California: U.S. Geological Survey Open-File Report 2018–1191, 2 sheets, scale 1:100,000, https://doi.org/10.3133/ofr20181191.

ISSN: 2331-1258 (online)

Study Area

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Geologic map and database of the Chocolate Mountain Aerial Gunnery Range, Riverside and Imperial Counties, California
Series title Open-File Report
Series number 2018-1191
DOI 10.3133/ofr20181191
Year Published 2018
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 2 Sheets: 41.00 x 36.34 inches and 44.00 x 40.00 inches; Database; Metadata
Country United States
State California
County Imperial County, Riverside County
Other Geospatial Chocolate Mountain Aerial Gunnery Range
Online Only (Y/N) Y
Additional Online Files (Y/N) Y