Print this pageABSTRACT: Structural Investigations at the Coso Geothermal Area Using Remote Sensing Information, Inyo County, California
Ward H. Austin
Remote sensing studies have been made in and adjacent to the Coso geothermal field using TM FCC satellite imagery, 1:100000 scale, U. S. Geological Survey orthophotos, 1:24000 scale, and proprietary black-and-white photography by California Energy Company, Inc., at various scales including black-and-white positive film transparencies at a scale of 1:6000. These studies have been made in an attempt to understand the complex geology seen on the surface and to try to improve the method of locating geothermal wells.
The tectonic history indicated by remote sensing, gravity, magnetic, refraction and reflection seismic studies indicates structure caused by a period of thrusting and folding followed by local and regional slumping and collapse, which is continuing today. During Sevier/Laramide orogeny, the Sierra Nevada Mountains were thrust eastward over Rose Valley/Indian Wells Valley. Relatively thin granitic/metamorphic plates were folded to form the Coso Range and thrust eastward over Coso Wash. In turn, the Argus Range to the east was thrust eastward over Panamint Valley.
As soon as topographic relief, developed by the thrusting, was high enough, the entire area started to collapse, in some cases using the original thrust planes for slumping. The granitic/metamorphic rocks forming the surface of the Coso Range anticline slumped eastward into Coso Wash and westward toward Rose Valley. The Sierra front slumped eastward into Rose Valley/Indian Wells Valley, and the entire range may have slid westward on the original thrust faults. The thin basalts on the east side of Coso Wash slumped westward into Coso Wash. Several basaltic eruptions of 3-4 million years ago used the zone between slump blocks as eruption sites. Regional slumping for the entire area toward the southeast is indicated on satellite imagery.
AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990