Citation:

Abraham, J. D., A. Legtchenko, A T. Mazzella, E. White, AND J. B. Fleming. TDEM AND NUMIS (PLUS) SOUNDINGS AT THE ASH MEADOWS NATIONAL WILDLIFE REFUGE: A CASE STUDY. Presented at 2nd International Workshop on the Magnetic Resonance Sounding Method Applied to Non-Invasive Groundwater Investigations, Orleans, France, November 19-21, 2003.

Impact/Purpose:

Research is being conducted to improve and evaluate the resolution of the CR, EM, seismic, and GPR methods over complex geological formations (such as fractured geologies) and to evaluate the capability of these geophysical methods to delineate subsurface organic contaminants.

Description:

During the summer of 2002, a cooperative project between the U.S. Geological Survey, the U.S. Environmental Protection Agency, and the Bureau de Recherches Geologiques et Minieres was undertaken to evaluate and gain knowledge of the Iris NUMIS instrument. The system was deployed at several sites throughout the United States of America (USA). One of these sites was the Ash Meadows National Wildlife Refuge. The following describes the geology, hydrology , and geophysical results (including NUMIS and time-domain electromagnetic soundings) in this unique desert oasis environment. Ash Meadows is located in southern Nye County, Nevada approximately 145 kIn northwest of Las Vegas, Nevada. Ash Meadows lies within the southern part of the Great Basin, an internally drained subdivision of the Basin and Range physiographic province. TDEM soundings were collected at each of the NUMIS site locations. The TDEM results clearly show the resistive carbonate fault blocks as well as a horizontal resistive layer that is broken by faults. These TDEM soundings provided a resistivity section for input into the NUMIS inversions. The NUMIS inversions indicate several water rich zones throughout the Ash Meadows area. Resource managers will use the results from this study to improve the hydrologic model of the Ash Meadows.

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