Ground-magnetic studies of the Amargosa Desert region, California and Nevada

ABSTRACT High-resolution aeromagnetic surveys of the Amargosa Desert region, California and Nevada, exhibit a diverse,array of magnetic,anomalies reflecting a wide,range of mid- and upper-crustal lithologies. In most cases, these anomalies can be interpreted in terms of exposed rocks and sedimentary,deposits. More ,difficult to explain ,are linear magnetic ,anomalies ,situated over lithologies that typically have very low magnetizations. Aeromagnetic anomalies are observed, for example, over thick sections of Quaternary alluvial deposits and spring deposits associated with past or modern ground-water discharge in Ash Meadows, Pahrump Valley, and Furnace Creek Wash. Such deposits are typically considered nonmagnetic. To help determine the source ofthese aeromagnetic anomalies, we conducted ground-magnetic studies at five areas: near Death Valley Junction, at Point of Rocks Spring, at Devils Hole, at Fairbanks Spring, and near Travertine Springs. Depth-to-source calculations show that the sources of these ,anomalies lie within the Tertiary and Quaternary sedimentary ,section. We,conclude that they are caused by discrete volcanic units lying above the pre-Tertiary basement. , At Death Valley Junction and Travertine Springs, these concealed volcanic units are probably part of the Miocene Death Valley volcanic field exposed in the nearby Greenwater Range and Black Mountains. The linear nature of the aeromagnetic,anomalies suggests that these concealed volcanic rocks are bounded and offset by near-surface faults. Cover photo: Greenwater Range, Death Valley National Park. View is to west from Ash Meadows. Note