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Title: Gravity and magnetic study of the Pahute Mesa and Oasis Valley region, Nye County, Nevada

Abstract

Regional gravity and aeromagnetic maps reveal the existence of deep basins underlying much of the southwestern Nevada volcanic field, approximately 150 km northwest of Las Vegas. These maps also indicate the presence of prominent features (geophysical lineaments) within and beneath the basin fill. Detailed gravity surveys were conducted in order to characterize the nature of the basin boundaries, delineate additional subsurface features, and evaluate their possible influence on the movement of ground water. Geophysical modeling of gravity and aeromagnetic data indicates that many of the features may be related to processes of caldera formation. Collapse of the various calderas within the volcanic field resulted in dense basement rocks occurring at greater depths within caldera boundaries. Modeling indicates that collapse occurred along faults that are arcuate and steeply dipping. There are indications that the basement in the western Pahute Mesa - Oasis Valley region consists predominantly of granitic and/or fine-grained siliceous sedimentary rocks that may be less permeable to ground-water flow than the predominantly fractured carbonate rock basement to the east and southeast of the study area. The northeast-trending Thirsty Canyon lineament, expressed on gravity and basin thickness maps, separates dense volcanic rocks on the northwest from less dense intracaldera accumulationsmore » in the Silent Canyon and Timber Mountain caldera complexes. The sources of the lineament is an approximately 2-km wide ring fracture system with step-like differential displacements, perhaps localized on a pre-existing northeast-trending Basin and Range fault. Due to vertical offsets, the Thirsty Canyon faults zone probably juxtaposes rock types of different permeability and, thus, it may act as a barrier to ground-water flow and deflect flow from Pahute Mesa along its flanks toward Oasis Valley. Within the Thirsty Canyon fault zone, highly fractured rocks may serve also as a conduit, depending upon the degree of alteration and its effect on porosity and permeability. In the Oasis Valley region, other structures that may influence ground-water flow include the western and southern boundaries of the Oasis Valley basin, where the basement abruptly shallows.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
United States Geological Survey - Nevada, Las Vegas, NV (US)
Sponsoring Org.:
USDOE Nevada Operations Office (US)
OSTI Identifier:
10449
Alternate Identifier(s):
OSTI ID: 10449
Report Number(s):
USGS OFR 99-303
TRN: AH200126%%377
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 31 Aug 1999
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; BASEMENT ROCK; CARBONATE ROCKS; GEOLOGIC STRUCTURES; GRAVITY SURVEYS; GROUND WATER; PERMEABILITY; POROSITY; SEDIMENTARY ROCKS; THICKNESS OASIS VALLEY; NEVADA; GEOHYDROLOGY; AEROMAGNETIC DATA; GRAVITY DATA; PAHUTE MESA

Citation Formats

Dixon, G.L., Fridrich, C.J., Hildenbrand, T.G., Laczniak, R.J., Mankinen, E.A., and McKee, E.H. Gravity and magnetic study of the Pahute Mesa and Oasis Valley region, Nye County, Nevada. United States: N. p., 1999. Web. doi:10.2172/10449.
Dixon, G.L., Fridrich, C.J., Hildenbrand, T.G., Laczniak, R.J., Mankinen, E.A., & McKee, E.H. Gravity and magnetic study of the Pahute Mesa and Oasis Valley region, Nye County, Nevada. United States. doi:10.2172/10449.
Dixon, G.L., Fridrich, C.J., Hildenbrand, T.G., Laczniak, R.J., Mankinen, E.A., and McKee, E.H. Tue . "Gravity and magnetic study of the Pahute Mesa and Oasis Valley region, Nye County, Nevada". United States. doi:10.2172/10449. https://www.osti.gov/servlets/purl/10449.
@article{osti_10449,
title = {Gravity and magnetic study of the Pahute Mesa and Oasis Valley region, Nye County, Nevada},
author = {Dixon, G.L. and Fridrich, C.J. and Hildenbrand, T.G. and Laczniak, R.J. and Mankinen, E.A. and McKee, E.H.},
abstractNote = {Regional gravity and aeromagnetic maps reveal the existence of deep basins underlying much of the southwestern Nevada volcanic field, approximately 150 km northwest of Las Vegas. These maps also indicate the presence of prominent features (geophysical lineaments) within and beneath the basin fill. Detailed gravity surveys were conducted in order to characterize the nature of the basin boundaries, delineate additional subsurface features, and evaluate their possible influence on the movement of ground water. Geophysical modeling of gravity and aeromagnetic data indicates that many of the features may be related to processes of caldera formation. Collapse of the various calderas within the volcanic field resulted in dense basement rocks occurring at greater depths within caldera boundaries. Modeling indicates that collapse occurred along faults that are arcuate and steeply dipping. There are indications that the basement in the western Pahute Mesa - Oasis Valley region consists predominantly of granitic and/or fine-grained siliceous sedimentary rocks that may be less permeable to ground-water flow than the predominantly fractured carbonate rock basement to the east and southeast of the study area. The northeast-trending Thirsty Canyon lineament, expressed on gravity and basin thickness maps, separates dense volcanic rocks on the northwest from less dense intracaldera accumulations in the Silent Canyon and Timber Mountain caldera complexes. The sources of the lineament is an approximately 2-km wide ring fracture system with step-like differential displacements, perhaps localized on a pre-existing northeast-trending Basin and Range fault. Due to vertical offsets, the Thirsty Canyon faults zone probably juxtaposes rock types of different permeability and, thus, it may act as a barrier to ground-water flow and deflect flow from Pahute Mesa along its flanks toward Oasis Valley. Within the Thirsty Canyon fault zone, highly fractured rocks may serve also as a conduit, depending upon the degree of alteration and its effect on porosity and permeability. In the Oasis Valley region, other structures that may influence ground-water flow include the western and southern boundaries of the Oasis Valley basin, where the basement abruptly shallows.},
doi = {10.2172/10449},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {8}
}