Master of Science (MS)
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The Basin and Range province is characterized by normal faults associated with
extension, but the occurrence of strike-slip faults and the seismic hazard accompanying
them is less understood. One major strike-slip zone, the Pahranagat shear zone (PSZ),
lies in Lincoln County, Nevada and within the boundary zone between northern Basin
and Range (NBR) and central Basin and Range (CBR) sub-provinces. The PSZ is a 20-
25 km long zone of Cenozoic left-lateral faults. The Arrowhead Mine Fault (AMF) is one
of the three major faults in the PSZ. The western AMF and the faults that surround and
abut it are the foci of this research. The purpose of this research is to understand the
timing and style of deformation of the AMF, the PSZ, and the relationship of the PSZ to
regional tectonics. I hypothesize that the AMF is a recent tectonic feature that supports
a model of regional sinistral transfer between tectonic regimes. The best way to obtain
the spatial and geometric data needed to address the issue was detailed mapping with
emphasis on fault cross-cutting, termination, and kinematic relationships at 1:12,000
scale of the western AMF and surrounding area in the East Pahranagat Range.
New fault data, and stereographic analysis of bedding and compaction foliation data
along with cross sections and a fence diagram provide evidence that the normal faults
and strike-slip fault are kinematically compatible and were active synchronously,
indicating that the AMF is a transfer fault. Strike-slip fault splays form a flower
structure/duplex that are shown to have formed synchronously with a number of normal
faults in the area. Internally, the duplex contains both contractional and extensional
structures, divided by a through-going fault. This situation is uncommon in models of
duplex formation, but is suggested here to have formed during segment linkage.
Cross-cutting relationships indicate that the AMF cuts Kane Wash Tuff, Gregerson
Basin Member, along one strand, constraining the age to ~15 Ma or younger. By
constraining the age and style of deformation of the AMF we find that the PSZ was
active late in the development of the NBR to CBR boundary zone.
The PSZ plays a distinct role in the intraplate tectonics of the region, falling within the
Southern Nevada Seismic Belt. It may be facilitating strain transfer from other sinistral
structures within the Southern Nevada Seismic Belt (Caliente-Enterprise Zone, Rock
Valley Fault Zone, etc.). The presence of both a western termination of the AMF and a
gap in left-lateral structures to the west suggest that the NBR-CBR boundary is still
developing, which has implications for the interconnectivity of Walker Lane with the
Intermountain Seismic Belt and has implications for seismic hazard.
faulting; flower structure; nevada; Seismicity; structural; tectonics
Evans, Michael Dennis, "Structural evolution and regional implications of the Arrowhead Mine Fault within the Pahranagat shear zone, Nevada, USA" (2018). UNLV Theses, Dissertations, Professional Papers, and Capstones. 3248.