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Brief Report for Southern Death Valley fault zone, Confidence Hills section (Class A) No. 143a

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Compiled in cooperation with the California Geological Survey

citation for this record: Machette, M.N., and Piety, L.A., compilers, 2001, Fault number 143a, Southern Death Valley fault zone, Confidence Hills section, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, http://earthquakes.usgs.gov/hazards/qfaults, accessed 07/28/2014 06:20 AM.

Synopsis General: The Southern Death Valley fault zone (SDV) is comprised of dextral-slip faults that extend southeast from Cinder Hill and Shoreline Butte, both of which shows clear evidence of right-lateral offset. The SDV is the southern of four fault zones that comprise the much longer Death Valley fault system. From north to south, these include the north-trending Fish Lake fault zone [49] in western Nevada and easternmost California, the northwest-trending Northern Death Valley fault zone [141], the north-trending Black Mountains fault zone [142], and the Southern Death Valley fault zone [143]. It has been long proposed that right-lateral displacement on the northwest-striking SDV [143] and NDV [141] fault zoned has resulted in tension that caused the two sides of Death Valley to pull apart along the north-trending Black Mountains fault zone [142], thus forming the deep trough of the present Death Valley. The SDV is distinguished from the Black Mountains fault zone by its more northwesterly trend (about N 40? W) and almost pure dextral sense of slip. Neogene movement on the SDV has offset upper Cenozoic to Quaternary volcanic and sedimentary deposits throughout southern Death Valley (its namesake). Estimates of the total right-lateral displacement on the SDV range between 8 km (in Quaternary sediment) and about 50 km (in old rocks). These estimates are based on a variety of stratigraphic and structural markers of different ages. The SDV can be traced southeast to nearly the Garlock fault zone [69], where it is truncated, bent and has had young reverse slip on some of its strands. An offset continuation of the SDV may extend as far south to the Bristol and Old Dad Mountains, although it is unclear whether or not there is Quaternary movement along this portion of the fault zone. Much of the SDV is characterized by very linear right-lateral fault traces with abundant evidence for Holocene surface ruptures. The Confidence Hills are sandwiched between two strands of the SDV, which has resulted in strong deformation and folding of the sediments. South of the Confidence Hills, the SDV begins to splay out into several strands as it approaches the Garlock fault zone. Holocene activity on two main strands appears to die out near the north end of the Noble Hills, but several additional traces with Quaternary displacement extend to within a few kilometers of the Garlock fault zone.

Sections: This fault has 2 sections. Owing to changes in fault position, complexity, and evidence for young movement, we have subdivided the Southern Death Valley fault zone into two sections. The northern (Confidence Hills) section extends from the north margin of Cinder Hill to the south end of the Confidence Hills (ca. N 35?50') as suggested by Wright and Troxel (1984 #1700). The southern (Nobel Hills) section continues south from the Confidence Hills through and along the Nobel Hills to the northern margin of the Avawatz Mountains and its junction with the Garlock fault zone [69]. This point is roughly coincident with the boundaries between T. 18/17 N. and R. 5/6 E. The fault zone may continue further south to the Soda Mountains as suggested by Brady (1988 #1452), where evidence for young movement on the fault appears to be buried beneath sediment of Silver Lake playa. However, there does not appear to be abundant evidence for Quaternary movement along this extension of the fault, and thus this portion of the SDV is not included herein.
County(s) and State(s) INYO COUNTY, CALIFORNIA
Physiographic province(s) BASIN AND RANGE
Length (km) This section is 18 km of a total fault length of 50 km.
Average strike N43°W (for section) versus N43°W (for whole fault)
Sense of movement Dextral
Dip Direction NE; V
Historic earthquake
Most recent prehistoric deformation Latest Quaternary (<15 ka)
Slip-rate category Between 1.0 and 5.0 mm/yr
Date and Compiler(s) 2001
Michael N. Machette, U.S. Geological Survey
Lucy A. Piety, U.S. Bureau of Reclamation