GEOPHYSICAL INVESTIGATIONS TO SUPPORT THE REGIONAL GROUNDWATER STUDIES OF DEATH VALLEY IN INYO COUNTY, CALIFORNIA

Inyo County, through a Cooperative Agreement program funding by the US Department of Energy, has been conducting a research program to prove groundwater movement through the Paleozoic Carbonates from the Amargosa Valley through the Southern Funeral Mountains to the major spring in Death Valley. Our study culminated in a MODFLOW groundwater model that is supported by our current program of: 1) monitoring well drilling in the Southern Funeral Mountains, 2) surface and subsurface geologic mapping in the area, and 3) geophysical surveys.<br>The goal of the geophysical survey program was to characterize the complex geological structure of the Southern Funeral range to assist with the siting of monitoring wells in the Paleozoic carbonate aquifer system. A total of 87 miles of gravity data and 66 TEM soundings were collected. The surface of the bedrock in the Amargosa Valley interpreted from the gravity data indicates that the basin and range fault blocks of the Southern Funeral Mountains project into the valley under the valley fill, but that the fault blocks are broken into isolated strands of the State Line Fault System. The result is a series of steep sided blocks of bedrock that rise close to the valley surface, surrounded by areas where the bedrock is in excess of 6,000 feet deep.<br>The geophysical survey program was successful in characterizing the subsurface structure configuration of the Paleozoic carbonate aquifer, and allowed the siting of the monitoring wells to penetrate the carbonate aquifer at an acceptable depth.