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.
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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Isostatic residual gravity map of the eastern half of the Big Bear Lake 100,000 quadrangle. Click on Gravity Map button for additional versions. |
1 U.S. Geological Survey, MS 989, 345 Middlefield Road, Menlo Park, CA 94025
2 Geothermal Program Office, Code 83G000D, Naval Air Weapons Station, China Lake, CA 93555
3 U.S. Geological Survey, 5735 Kearny Villa Rd., San Diego, CA 92123
This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes and does not imply endorsement by the U.S. Government.
