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Open-File Report 2013–1024-B

Prepared in cooperation with the U.S. Army, Fort Irwin National Training Center

Generalized Surficial Geologic Map of the Fort Irwin Area, San Bernardino County, California

By David M. Miller, Christopher M. Menges, and David J. Lidke

Thumbnail of and link to report PDF (298 kB)Abstract

The geology and landscape of the Fort Irwin area, typical of many parts of the Mojave Desert, consist of rugged mountains separated by broad alluviated valleys that form the main coarse-resolution features of the geologic map. Crystalline and sedimentary rocks, Mesozoic and older in age, form most of the mountains with lesser accumulations of Miocene sedimentary and volcanic rocks. In detail, the area exhibits a fairly complex distribution of surficial deposits resulting from diverse rock sources and geomorphology that has been driven by topographic changes caused by recent and active faulting. Depositional environments span those typical of the Mojave Desert: alluvial fans on broad piedmonts, major intermittent streams along valley floors, eolian sand dunes and sheets, and playas in closed valleys that lack through-going washes. Erosional environments include rocky mountains, smooth gently sloping pediments, and badlands in readily eroded sediment. All parts of the landscape, from regional distribution of mountains, valleys, and faults to details of degree of soil development in surface materials, are portrayed by the surficial geologic map. Many of these attributes govern infiltration and recharge, and the surface distribution of permeable rock units such as Miocene sedimentary and volcanic rocks provides a basis for evaluating potential groundwater storage. Quaternary faults are widespread in the Fort Irwin area and include sinistral, east-striking faults that characterize the central swath of the area and the contrasting dextral, northwest-striking faults that border the east and west margins. Bedrock distribution and thickness of valley-fill deposits are controlled by modern and past faulting, and faults on the map help to identify targets for groundwater exploration.

First posted November 26, 2014

This report is only available on-line

Back to Geology and Geophysics Applied to Groundwater Hydrology at Fort Irwin, California

For additional information, contact:
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U.S. Geological Survey
345 Middlefield Road, MS 901
Menlo Park, CA 94025-3591
http://geomaps.wr.usgs.gov/gmeg/

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Suggested citation:

Miller, D.M., Menges, C.M., and Lidke, D.J., 2014, Generalized surficial geologic map of the Fort Irwin area, San Bernardino County, California, chap. B of Buesch, D.C., ed., Geology and geophysics applied to groundwater hydrology at Fort Irwin, California: U.S. Geological Survey Open-File Report 2013–1024, 11 p., scale 1:100,000, http://dx.doi.org/10.3133/ofr20131024B.

ISSN 2331-1258 (online)


Contents

Abstract

Introduction

Mapping Methods

Map Classification

Map Units

Quaternary Faults

Acknowledgments

Description of Map Units

References

Figures (1)

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