GEOPHYSICAL INVESTIGATION OF HOT SPRINGS IN THE VICINITY OF SHOSHONE, CALIFORNIA

Hot springs are located in the Death Valley Region of California primarily along the Amargosa river. A previous geophysical investigation conducted by Wamalwa in the town of Tecopa and near Saratoga springs along the Amargosa river suggested that deep faults must intersect with an appropriate orientation relative to the regional stress field in order to create hot springs along the river. The river was interpreted to follow the main deep fault system. This research tests that hypothesis in the vicinity of Shoshone, California using magnetic and gravity surveys. The results of our surveys support Wamalwa’s hypothesis based on the identified intersecting faults of the appropriate orientation associated with the Shoshone hot spring. Faults were also identified at places with no evidence of hot springs and this could be due to the presence of thicker sediments preventing the springs from flowing to the surface. An alternative possibility is that the faults are not deep enough to tap the hot water that would produce a hot spring. The geophysical surveys also indicated there were three distinct basalt mounds near the Shoshone hot springs that have different properties. Two of these mounds are characterized by low magnetic and low Bouguer gravity anomalies. The third mound corresponds to a high Bouguer gravity and high magnetic anomaly. This observation suggests that there were at least two different episodes of basalt emplacement. The deepest part of the Tecopa basin in the study area was identified as a region with a low Bouguer anomaly and an associated magnetic high. These properties suggest the basin fill includes highly vesicular basalts which would give the low density. This interpretation is supported by the extensive pyroclastic tuffs in the region. Generally regions of high magnetic anomalies also have high Bouguer anomalies and this indicates the possible existence of buried igneous rocks in the region. These rocks are mainly seen closer to the Dublin, Sperry and Alexander Hills. The low magnetic anomalies are mainly seen in the regions of thicker sedimentary deposits such as in the Resting Springs range where Precambrian and Paleozoic sedimentary rocks are preserved.