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Implications of geophysical analysis on basin geometry and fault offsets in the northern Colorado River extensional corridor and adjoining Lake Mead region, Nevada and Arizona

Victoria E. Langenheim, L. Sue Beard and James E. Faulds
Implications of geophysical analysis on basin geometry and fault offsets in the northern Colorado River extensional corridor and adjoining Lake Mead region, Nevada and Arizona (in Miocene tectonics of the Lake Mead region, central Basin and Range, Paul J. Umhoefer (editor), L. Sue Beard (editor) and Melissa A. Lamb (editor))
Special Paper - Geological Society of America (June 2010) 463: 39-59

Abstract

The northern Colorado River extensional corridor and Lake Mead region are characterized by prominent gravity and magnetic anomalies that provide insight into the geometry of extensional basins, amount of vertical and strike-slip offset on faults that bound these basins, and composition of major basement blocks. Although large-magnitude extension throughout the extensional corridor and major strike-slip faulting north of Lake Mead have highly disrupted many basins, most of the older basins (middle to late Miocene) are not associated with prominent geophysical anomalies. Instead, the most conspicuous anomalies (e.g., gravity lows) generally correspond to the younger (late Miocene to recent), structurally more coherent basins. Most of the geophysically expressed basins lie north of Lake Mead and are bounded by Quaternary normal and/or strike-slip fault zones. Both Quaternary faults and geophysically conspicuous basins are largely absent south of Lake Mead, where the only prominent gravity low corresponds to a structurally intact basin filled primarily with halite along the less extended, eastern margin of the corridor. Relatively continuous northeast-trending magnetic anomalies south of Lake Mead, presumably caused by Proterozoic basement rocks, suggest that strike-slip displacement is negligible on many of the major normal faults. In contrast, magnetic anomalies are smeared along the Lake Mead fault system and Las Vegas Valley shear zone. Offset anomalies suggest left-lateral displacement of 12-20 km for the Hamblin Bay fault zone, 12-15 km for the Lime Ridge fault, and 12 km on the Gold Butte fault. These values are compatible with or lower than published estimates based on geologic mapping.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 463
Title: Implications of geophysical analysis on basin geometry and fault offsets in the northern Colorado River extensional corridor and adjoining Lake Mead region, Nevada and Arizona
Title: Miocene tectonics of the Lake Mead region, central Basin and Range
Author(s): Langenheim, Victoria E.Beard, L. SueFaulds, James E.
Author(s): Umhoefer, Paul J.editor
Author(s): Beard, L. Sueeditor
Author(s): Lamb, Melissa A.editor
Affiliation: U. S. Geological Survey, Menlo Park, CA, United States
Affiliation: Northern Arizona University, Department of Geology, Flagstaff, AZ, United States
Pages: 39-59
Published: 201006
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 105
Accession Number: 2010-088814
Categories: Structural geologyApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
N35°00'00" - N36°40'00", W115°30'00" - W113°30'00"
Secondary Affiliation: U. S. Geological Survey, USA, United StatesUniversity of Saint Thomas, USA, United StatesUniversity of Nevada, Reno, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201047
Program Name: USGSOPNon-USGS publications with USGS authors
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