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GEOREF RECORD

Dextral, normal, and sinistral faulting across the eastern California shear zone-Mina deflection transition, California-Nevada, USA

Kevin DeLano, Jeffrey Lee, Rachelle Roper and Andrew T. Calvert
Dextral, normal, and sinistral faulting across the eastern California shear zone-Mina deflection transition, California-Nevada, USA
Geosphere (Boulder, CO) (June 2019) 15 (4): 1206-1239

Abstract

Strike-slip faults commonly include extensional and contractional bends and stepovers, whereas rotational stepovers are less common. The Volcanic Tableland, Black Mountain, and River Spring areas (California and Nevada, USA) (hereafter referred to as the VBR region) straddle the transition from the dominantly NW-striking dextral faults that define the northwestern part of the eastern California shear zone into a rotational stepover characterized by dominantly NE-striking sinistral faults that define the southwestern Mina deflection. New detailed geologic mapping, structural studies, and (super 40) Ar/ (super 39) Ar geochronology across the VBR region allow us to calculate Pliocene to Pleistocene fault slip rates and test predictions for the kinematics of fault slip transfer into this rotational stepover. In the VBR, Mesozoic basement is nonconformably overlain by a Miocene sequence of rhyolite, dacite, and andesite volcanic rocks that yield (super 40) Ar/ (super 39) Ar ages between 22.878 + or - 0.051 Ma and 11.399 + or - 0.041 Ma. Miocene rocks are unconformably overlain by an extensive sequence of Pliocene basalt and andesite lava flows and cinder cones that yield (super 40) Ar/ (super 39) Ar ages between 3.606 + or - 0.060 Ma and 2.996 + or - 0.027 Ma. The Pliocene sequence is, in turn, unconformably overlain by Quaternary tuffs and sedimentary rocks. This sequence of rocks is cut by NS- to NW-striking normal faults across the Volcanic Tableland that transition northward into NS-striking normal faults across the Black Mountain area and that, in turn, transition northward into NW-striking dextral and NE-striking sinistral faults in the River Spring area. A range of geologic markers were used to measure offset across the faults in the VBR, and combined with the age of the markers, yield minimum ?EW-extension rates of approximately 0.5 mm/yr across the Volcanic Tableland and Black Mountain regions, and minimum NW-dextral slip and NE-sinistral slip rates of approximately 0.7 and approximately 0.3 mm/yr, respectively, across the River Spring region. In the River Spring area, our preferred minimum dextral slip and sinistral slip rates are 0.8-0.9 mm/yr and 0.7-0.9 mm/yr, respectively. We propose three kinematic fault slip models, two irrotational and one rotational, whereby the VBR region transfers a portion of dextral Owens Valley fault slip northwestward into the Mina deflection. In irrotational model 1, Owens Valley fault slip is partitioned into two components, one northeastward onto the White Mountain fault zone and one northwestward into the Volcanic Tableland. Slip from the two zones is then transferred northward into the southwestern Mina deflection. In irrotational model 2, Owens Valley fault slip is partitioned into three components, with the third component partitioned west-northwest onto the Sierra Nevada frontal fault zone. In the rotational model, predicted sinistral slip rates across the southwestern Mina deflection are at least 115% greater than our observed minimum slip rates, implying our minimum observed rates underestimate true sinistral slip rates. A comparison of summed geologic fault slip rates, parallel to motion of the Sierra Nevada block relative to the central Great Basin, from the Sierra Nevada northeastward across the VBR region and into western Nevada are the same as geodetic rates, if our assumptions about the geologic slip rate across the dextral White Mountain fault zone is correct.


EISSN: 1553-040X
Serial Title: Geosphere (Boulder, CO)
Serial Volume: 15
Serial Issue: 4
Title: Dextral, normal, and sinistral faulting across the eastern California shear zone-Mina deflection transition, California-Nevada, USA
Affiliation: Central Washington University, Department of Geological Sciences, Ellensburg, WA, United States
Pages: 1206-1239
Published: 20190624
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 87
Accession Number: 2019-068720
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., 4 tables, geol. sketch maps
N35°00'00" - N42°00'00", W120°00'00" - W114°04'60"
N32°30'00" - N42°00'00", W124°30'00" - W114°15'00"
Secondary Affiliation: U. S. Geological Survey, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201936
Program Name: USGSOPNon-USGS publications with USGS authors
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