Geophysical investigation of hot springs in the vicinity of Shoshone, California

Magnetic and gravity surveys were conducted in the vicinity of Shoshone, California to test a hypothesis from investigating hotsprings within Tecopa and Saratoga which states that deep faults must intersect with a specific orientation relative to the regional stress field in order to create hot springs along the Amargosa River. Three isolated basalt flows with different gravity and magnetic properties were identified near the Shoshone hot spring. Two of the flows have very low magnetic anomalies and the remaining one has a high magnetic anomaly. The high magnetic anomaly basalt flow also has a significantly higher Bouguer anomaly than the other two flows associated with the low magnetic anomalies. These observations suggest that the flows were formed by different time volcanic activity with the low magnetic anomaly basalts cooling during a magnetic reversal and the high magnetic anomaly basalt cooling during normal magnetic era. The deepest part of the Tecopa basin in the study area was identified as a region with low Bouguer anomaly and associated magnetic high. These properties suggest the basin fill includes highly vesicular basalts which would give the low density. Generally regions of high magnetic anomalies also have high Bouguer anomalies which indicate the possible existence of igneous rocks in the region. 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. From the magnetic and gravity surveys, this research support the testing 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