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U.S. Geological Survey Open-File Report 02-353
Gravity map and data of the eastern half of the Big Bear Lake, 100,000 scale quadrangle, California and analysis of the depths of several basins.by Carter Roberts1, Robert Jachens1, Allan Katzenstein2, Gregory Smith3 and Russell Johnson3
Gravity surveys are useful tools for helping to understand the 3-dimensional geology of an area. Many gravity measurements were made in the 1960s and 1970s by various groups in order to produce gravity maps covering California at a scale of 1:250,000 for the California Division of Mines and Geology. (For this area see Biehler et. al. 1988.) More recent surveys have focused on specific areas and problems. This report includes new data on the southern portion of the Marine Corps Air Ground Combat Center (MCAGCC) Twentynine Palms and the Yucca Valley-Joshua Tree-Twentynine Palms area and presents the map and basin analyses that were prepared with these data. This map shows the location of the MCAGCC with the area covered by the gravity map in red.
The gravity field, shown below as isostatic anomalies, reflects density
variations of the Earth's upper and middle crust. Gravity highs occur
over crystalline bedrock. Gravity lows occur over Cenozoic (younger) sedimentary
rocks.
Gravity gradients commonly occur where faults have juxtaposed rocks
of different densities. However, faults are not always marked by gravity
gradients, as rocks of similar densities may be juxtaposed along a fault.
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Privacy statement / General Disclaimer U.S. Department of the Interior This site was produced by the Western Earth Surface Processes team (Geologic Division) of the U.S. Geological Survey The URL of this page is http://geopubs.wr.usgs.gov/open-file/of02-353/bigbearlakeeast.html Contact: croberts@usgs.gov Site last updated September 30, 2002 |