title: Mesozoic Sevier Thrusts Overprinted by Miocene-Quaternary Left-Lateral Deformation: Structures and Tectonism of the Kane Springs Wash Region, Nevada
Creators: name: Reid, Andrew
Publisher: name: University of Nevada, Las Vegas
Year: 2022

description: Recognizing how rifts develop through space and time is vital to enrich our understanding of continental breakup. Rifts are commonly segmented by transfer or accommodations zones that form as the rift develops due to differences in the onset, direction, magnitude, or rates of extension on either side of the transfer or accommodation zone. The Basin and Range province is a wide rift where Cenozoic extension overprints and exposes earlier Mesozoic Sevier fold-thrust belt shortening structures. This exposure allows Sevier thrust correlations between individual mountain ranges and use of these shortening structures to study rift segmentation by strike-slip transfer faults. The purpose of this study is to further develop our understanding of regional tectonism by unraveling the tectonic history of the Kane Springs Wash area, Nevada, from Sevier shortening and hinterland highland development, through highland erosion, and finally to overprinting by Miocene-Quaternary strike-slip and normal faults associated with rift segmentation. Focus is placed on clarifying (1) long term issues in the reconstruction of Sevier-related thrusts and the former Sevier hinterland; and (2) the development of a boundary zone within the Basin and Range province that contains strike-slip faults and whether it may be a rift segment boundary. Sevier thrusts exposed in the Delamar and Meadow Valley mountains are offset by a major Cenozoic left-lateral fault, the Kane Springs Wash fault that lies at the southern reach of the boundary zone between the Northern and Central Basin and Range subprovinces. This boundary zone is spatially coincident with the southern Nevada seismic belt where distinct changes in topography, style of deformation, rock exposures, and gravity anomalies occur/ These changes and the structures, together, suggest that the zone may operate as a rift segment boundary. Using new geologic mapping, detrital zircon ages, and structural analyses, I illustrate several key findings. (1) The left-lateral Kane Springs Wash fault is a transfer fault that separates two distinct domains of extension on either side. (2) The Kane Springs Wash fault zone lies at the southern reach of the boundary zone between the Northern and Central Basin and Range subprovinces, helping to accommodate differences in slip across the broad boundary zone in conjunction with other ~E-W striking structures. (3) The newly dated Eocene conglomeratic sediments, ~39 Ma, that overlie Sevier-related thrusts, show that the earlier Sevier hinterland highland lies to the North and West of the Kane Springs Wash area. (4) The Delamar and Meadow Valley thrusts are distinct faults and the Dry Lake thrust is the southward lateral equivalent of the Delamar thrust. That correlation provides southward continuity to a major regional thrust sheet and requires it to be placed in regional reconstructions where it has rarely been included. Two major findings are drawn from this work. (1) The classification of the NBR-CBR boundary zone as a segment boundary within the Basin and Range is novel yet needed to better understand how the rift developed though time. (2) The southward correlation of the Delamar-Wah-Wah system to the Dry Lake system is new and furthers our understating of the architecture of the Sevier retroarc-fold-thrust-belt particularly because this large thrust system has been inappropriately minimized in regional reconstructions.