Ground-Magnetic Studies of the Amargosa Desert Region, California and Nevada

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 of these 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.
[Summary provided by the USGS.]