Preliminary Surficial Geologic Map Database of the Amboy 30x60 Minute Quadrangle, California By David R. Bedford, David M. Miller, and Geoffrey A. Phelps Open-File Report 2006–1165 U.S. Department of the Interior U.S. Geological Survey i U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey P. Patrick Leahy, Acting Director U.S. Geological Survey, Reston, Virginia 2006 Revised and reprinted: 2006 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Suggested citation: Bedford1, David R, Miller, David M. and Phelps, Geoff A., 2006, Preliminary Surficial Geologic Map Database of the Amboy 30x60 Minute Quadrangle, California: U.S. Geological Survey Open-File Report 2006-1165, Menlo Park, CA. 1. 345 Middlefield Rd MS973 Menlo Park, CA, 94025 Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. ii Contents Introduction .......................................................................................................................................... 1 Physiographic and Geologic Setting................................................................................................ 1 Previous Quaternary Studies ............................................................................................................ 2 Surficial Deposits ................................................................................................................................ 3 Material Properties............................................................................................................................. 3 Landscape History............................................................................................................................... 4 Quaternary Faulting and Tectonic Geomorphology .................................................................. 4 Quaternary Volcanism .................................................................................................................... 5 Eolian History.................................................................................................................................... 6 New Age Data in Fenner Wash and Bristol Lake ...................................................................... 6 Bristol Lake/Playa History.............................................................................................................. 9 Groundwater Discharge Deposits in Bristol Lake Basin.......................................................... 9 Evolution of Fenner Wash and Adjacent Piedmonts............................................................... 10 Description of Map Units ................................................................................................................. 11 Introduction .................................................................................................................................... 11 Surficial Deposits........................................................................................................................... 12 Anthropogenic Deposits........................................................................................................... 12 Alluvial Deposits ........................................................................................................................ 12 Wash Deposits ........................................................................................................................... 14 Eolian Deposits........................................................................................................................... 14 iii Mixed Eolian and Alluvial Deposits ........................................................................................ 15 Groundwater Discharge Deposits .......................................................................................... 15 Playa Deposits............................................................................................................................ 15 Axial Valley Deposits................................................................................................................. 15 Erosional Surfaces and Related Hillslope Deposits................................................................ 16 Hillslope Deposits: ................................................................................................................. 16 Pediment surfaces:................................................................................................................ 16 Volcanic rocks:............................................................................................................................... 17 Substrate materials....................................................................................................................... 17 Explanatory notes.......................................................................................................................... 18 Mapping methods...................................................................................................................... 18 Composite symbols.................................................................................................................... 18 Conventions for erosional environments............................................................................... 18 Quaternary faults ....................................................................................................................... 18 Data stations............................................................................................................................... 18 Acknowledgements .......................................................................................................................... 19 References Cited ............................................................................................................................... 19 Figures Figure 1: Location of the Amboy 30x60 Minute Quadrangle.....................................................23 Figure 2: Shaded relief image of the Amboy 30x60 Minute Quadrangle noting prominent physiographic features.....................................................................................................................24 iv Figure 3: Quaternary faults in the Amboy 30x60 Minute Quadrangle. A) Location of the Bristol-Granite Mountains fault cutting middle to early Pleistocene deposits, B) Location of the Bristol-Granite Mountains fault cutting late Pleistocene deposits, C) South Bristol Mountains fault cuts Pleistocene deposits, D) The Broadwell Lake fault cuts mid Pleistocene deposits, E) Ludlow fault cuts older Pleistocene deposits, F) Unnamed fault in the Northern Granite Mountains shows evidence of late Pleistocene rupture. ‘E-W’ fault and Hidden Valley fault are newly named faults.........................................................................25 Figure 4: Locations and relationships of chronologic information. A) Map of sample locations, B) Stragigraphic relations of alluvial deposits and luminescence sample in Fenner Wash, C) Stratigraphic relations of groundwater discharge deposits and luminescence samples near the town of Chambless.................................................................26 Figure 5: Evolution of Fenner Valley and Bristol Basin determined from surficial geologic mapping and field studies suggests the following chronology.................................................27 Tables Table 1: Preliminary Feldspar Infrared Stimulated Luminescence (IRSL) and Quartz Blue- light OSL Ages for Fenner Wash/Bristol Lake Area......................................................................8 v Surficial Geologic Map Database for the Amboy 30x60 Minute Quadrangle, California By David R. Bedford, David M. Miller, and Geoffrey A. Phelps Introduction The surficial geologic map database of the Amboy 30x60 minute quadrangle presents characteristics of surficial materials for an area approximately 5,000 km2 in the eastern Mojave Desert of California. This map consists of new surficial mapping conducted between 2000 and 2005, as well as compilations of previous surficial mapping. Surficial geology units are mapped and described based on depositional process and age categories that reflect the mode of deposition, pedogenic effects occurring post-deposition, and, where appropriate, the lithologic nature of the material. The physical properties recorded in the database focus on those that drive hydrologic, biologic, and physical processes such as particle size distribution (PSD) and bulk density. This version of the database is distributed with point data representing locations of samples for both laboratory determined physical properties and semi-quantitative field-based information. Future publications will include the field and laboratory data as well as maps of distributed physical properties across the landscape tied to physical process models where appropriate. The database is distributed in three parts: documentation, spatial map-based data, and printable