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The AAPG/Datapages Combined Publications Database

Pacific Section of AAPG

Abstract


The Geologic Transition, High Plateaus to Great Basin - A Symposium and Field Guide (The Mackin Volume), 2001
Pages 205-225

Basin Configuration of the Virgin River Depression, Nevada, Utah, and Arizona: A Geophysical View of Deformation Along the Colorado Plateau-Basin and Range Transition

V. E. Langenheim, R. G. Bohannon, J. M. Glen, R. C. Jachens, J. A. Grow, J. J. Miller, G. L. Dixon, T. C. Katzer

Abstract

The Virgin River Depression (VRD) is a large alluvial valley that conceals an unusually large and deep basin that straddles the states of Arizona, Nevada, and Utah, near the transition zone between the Colorado Plateaus and Basin and Range provinces. The basin configuration, based on a gravity inversion constrained by well and seismic-reflection data, indicates that the VRD consists of a western basin beneath Mormon Mesa and an eastern basin beneath the town of Mesquite, Nevada. The gravity inversion shows that the Mesquite basin can be separated into two subbasins divided by a ridge that parallels the Virgin River. The subbasin north of the Virgin River is rectangular in plan-view and very deep, reaching depths of 8 to 10 km. Quaternary north-striking faults are concentrated within the deeper portions of the subbasin. The subbasin south of the Virgin River trends northeast, parallel to mapped Quaternary faults. A concealed ridge between the two Mesquite subbasins coincides with a right step in the course of the Virgin River. The ridge may be caused by a compressional step in a left-lateral strike-slip fault system. The Mormon basin to the southwest, which reaches a depth of 5 km, is more elongated than the northern Mesquite subbasin to the northeast and thus, more similar to other basins of the Basin and Range province, especially north of the VRD. The geometry of faults imaged by seismic-reflection data within the VRD is similar to that of low- to moderate-angle normal faults mapped in the Mormon Mountains. Thus, the geometry of faulting mapped in the upper crust may not explain 12 km of relief on the Proterozoic surface. This observation, coupled with data indicating a relatively flat Moho throughout the Basin and Range province, suggests that crustal flow in the middle and lower crust played a major role in causing the great elevation differences of the Proterozoic surface in the VRD region.


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