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U.S. Geological Survey
Open-File Report 2005-1132
Version 1.0

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

By Richard J. Blakely, John W. Hillhouse, and Robert L. Morin


Cover photo of the Greenwater Range.  View is to the west from Ash Meadows.
Greenwater Range, Death Valley National Park. View is to west from Ash Meadows. Note gently dipping lava flows and interbedded tuffaceous beds, part of the Death Valley volcanic field.


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.

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Maintained by: Michael Diggles
Date created: April 5, 2005
Date last modified: June 9, 2008 (jmw)