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Scientific Investigations Map 3312

Surficial Geology and Stratigraphy of Pleistocene Lake Manix, San Bernardino County, California

By Marith C. Reheis, Joanna R. Redwine, Elmira Wan, John P. McGeehin, and D. Paco VanSistine

Thumbnail of and link to report PDF (5.7 MB)Abstract

Pluvial Lake Manix and its surrounding drainage basin, in the central Mojave Desert of California, has been a focus of paleoclimate, surficial processes, and neotectonic studies by the U.S. Geological Survey (USGS) since about 2004. The USGS initiated studies of Lake Manix deposits to improve understanding of the paleoclimatic record and the shifts in atmospheric circulation that controlled precipitation in the Mojave Desert. Until approximately 25,000 years ago, Lake Manix was the terminus of the Mojave River, which drains northeasterly from the San Bernardino Mountains; the river currently terminates in the Soda Lake and Silver Lake playas. Pleistocene Lake Manix occupied several subbasins at its maximum extent. This map focuses on the extensive exposures created by incision of the Mojave River and its tributaries into the interbedded lacustrine and alluvial deposits within the central (Cady) and northeastern (Afton) subbasins of Lake Manix, and extends from the head of Afton Canyon to Manix Wash. The map illuminates the geomorphic development and depositional history of the lake and alluvial fans within the active tectonic setting of the eastern California shear zone, especially interactions with the left-lateral Manix fault.

Lake Manix left an extraordinarily detailed but complex record of numerous transgressive-regressive sequences separated by desiccation and deposition of fan, eolian, and fluvial deposits, and punctuated by tectonic movements and a catastrophic flood that reconfigured the lake basin. Through careful observation of the intercalated lacustrine and fan sequences and by determining the precise elevations of unit contacts, this record was decoded to understand the response of the lake and river system to the interplay of climatic, geomorphic, and tectonic forces. These deposits are exposed in steep badland topography. Mapping was carried out mostly at scales of 1:12,000, although the map is presented at 1:24,000 scale, and employs custom unit nomenclature, with multiple subdivided lacustrine and alluvial fan units. In addition, many important units are very thin and cannot be mapped separately, or are covered by thin eolian sand, so these are commonly portrayed as stacks of units or combined units. These details are more accurately portrayed in the measured sections that accompany the map. Altitudes of many contacts were obtained using differentially corrected Global Positioning System (GPS) or, in some cases, lidar (light detection and ranging) data.

First posted December 15, 2014

  • Sheet 1 PDF (68.3 MB)
    Map of Surficial Geology and Stratigraphy of Pleistocene Lake Manix, San Bernardino County, California
  • Sheet 2 PDF (33.1 MB)
    Stratigraphic sections of Pleistocene Lake Manix map area, San Bernardino  County, California

For additional information, contact:
Director, Geosciences and Environmental Change Science Center
U.S. Geological Survey
Box 25046, Mail Stop 980
Denver, CO 80225
http://gec.cr.usgs.gov/

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Suggested citation:

Reheis, M.C., Redwine, J.R, Wan, Elmira, McGeehin, J.P., and VanSistine, D.P., 2014, Surficial Geology and Stratigraphy of Pleistocene Lake Manix, San Bernardino County, California: U.S. Geological Survey Scientific Investigations Map 3312, 46 p., 2 sheets, scale 1:24,000, https://dx.doi.org/10.3133/sim3312.

ISSN 2329-132X (online)



Contents

Abstract

Introduction

Physiographic Setting of Lake Manix

A Brief History of Pleistocene Lake Manix

Rationale for this Map

Description of Map Units

Acknowledgments

References Cited

Appendix. Captions for Selected Photographs of Pleistocene Lake Manix Map Area


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