Rates of extension along the Fish Lake Valley fault and

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Rates of extension along the Fish Lake Valley fault and transtensional deformation in the
eastern California shear zone - Walker Lane
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The oblique-slip normal-dextral Fish Lake Valley fault (FLVF) accommodates the
Plamen N. Ganev1,*
James F. Dolan1
Kurt L. Frankel2
Robert C. Finkel3, 4
1
Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089
School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA
30332
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Department of Earth and Planetary Science, University of California- Berkeley, Berkeley, CA
94720
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Centre Européen de Recherche et d’Enselignement des Géosciences de l’Environnement
(CEREGE), 13545 Aix en Provence, France
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*corresponding author: Plamen N. Ganev, 3651 Trousdale Parkway, Los Angeles, CA 90089.
[email protected], 213.740.8208
Keywords: neotectonics, eastern California shear zone, Fish Lake Valley fault, normal fault,
geochronology
ABSTRACT
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majority of Pacific-North America plate boundary deformation east of the San Andreas fault in
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the northern part of eastern California shear zone (ECSZ). New slip rates for the extensional
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component of the fault determined with LiDAR topographic data and 10Be geochronology of
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offset alluvial fans at Furnace Creek, Wildhorse Creek, Perry Aiken Creek, and Indian Creek
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indicate a northward increase in extension rate along the FLVF. Previous studies report
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cosmogenic 10Be ages of ~94 ka of the Furnace Creek alluvial fan and ~71 ka of the Indian
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Creek fan. New 10Be dates on from boulders at Wildhorse Creek and Perry Aiken Creek provide
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surface exposure ages of ~121 ka and ~71 ka, respectively. Assuming a 60º dip for the faults, the
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cumulative horizontal components of slip measured from the LiDAR data are 8.3 ± 0.4 m at
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Furnace Creek, 21.5 ± 1.1 m at Wildhorse Creek, 49.1 ± 2.5 m at Perry Aiken Creek, and 43.7 ±
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2.1 m at Indian Creek. These yield calculated late Pleistocene-Holocene horizontal extension
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rates of 0.1, 0.2, 0.7, and 0.6 mm/yr, respectively. Comparison of these rates with geodetic
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measurements of ~1 mm/yr of east-west extension across the northern ECSZ indicates that
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approximately half of the regional extension is accommodated by the FLVF. When summed with
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rates of extension on the White Mountains fault and Sierra Nevada frontal fault system, these
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data suggest that long-term geologic rates of deformation are commensurate with the short-term
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geodetic extension rate. The northward increase in Pleistocene extension rates is opposite the
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trend of the dextral slip rate along the FLVF, likey reflecting an extensional transfer zone in
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northern Fish Lake Valley that relays strain to the northeast across the Mina Deflection and into
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the Walker Lane.
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INTRODUCTION
The eastern California shear zone (ECSZ)- Walker Lane is an evolving fault system east
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of the San Andreas fault that accommodates ~20-25% (9-10 mm/yr) of Pacific-North America
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plate boundary deformation (e.g., Bennett et al., 2003; Dixon et al., 2000, 2003; Dokka and
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Travis, 1990; Faulds et al., 2005; Hearn and Humphreys, 1998; Humphreys and Weldon, 1994;
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McClusky et al., 2001; Miller et al., 2001; Thatcher et al., 1999; Wesnousky, 2005; Frankel et
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al., 2007a). The ECSZ is ~500 km long and extends northward from the San Andreas fault
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through the Mojave Desert, and along the east side of the Sierra Nevada. In the Mojave section
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of the ECSZ, fault motion is almost entirely right-lateral and slip is localized along several major
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north-northwest-striking faults (Oskin et al., 2008). North of the active left-lateral Garlock fault,
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motion is accommodated on four major fault systems: the Owens Valley, Panamint Valley-
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Saline Valley-Hunter Mountain, Death Valley-Fish Lake Valley, and Stateline fault zones (Fig.
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1; e.g., Frankel et al., 2008). In the northern part of the ECSZ, between latitude 37ºN and 38ºN,
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dextral motion between the stable Sierra Nevada block and North America is distributed from
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Long Valley Caldera in the west to the Silver Peak-Lone Mountain extensional complex in the
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east, with ~35% of the dextral shear being accommodated by the White Mountains and Fish
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Lake Valley faults (Kirby et al., 2006; Frankel et al., 2007a, b). Multiple northeast-striking,
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down-to-the-northwest normal faults transfer slip between the right-lateral Owens, Panamint
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Valley-Saline Valley-Hunter Mountain, and Death Valley-Fish Lake Valley fault systems (e.g.,
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Reheis and Dixon , 1996). North of the Mina deflection, strain is accommodated by a series of
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right-lateral faults as part of the Walker Lane belt (Wesnousky, 2005a, b).
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Although dextral shear accommodates most slip on the northwest-striking faults in Fish
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Lake Valley, fault segments that strike approximately north exhibit a relatively large extensional
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component of slip. Space-based geodetic studies demonstrate that the current strain field is
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consistent with transtensional deformation and indicate an extension rate of ~1 mm/yr measured
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normal to the predominant ~ N25ºW strike of the ECSZ at this latitude (e.g., Bennett et al. 2003;
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Savage et al., 2001; Wesnousky, 2005a). This geodetically-derived extension rate in the northern
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ECSZ is most likely distributed among the Sierra Nevada frontal fault, the Volcanic Tablelands,
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the White Mountains fault, and the Fish Lake Valley fault system (Fig. 1). The geologically-
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derived extension rates on the Sierra Nevada frontal fault (Le et al., 2006) and the White
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Mountains fault (Kirby et al., 2006) are both ~0.2 mm/yr. Therefore, if the geodetic and geologic
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rates of deformation are equal and the extensional component of the strain can be accounted for
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on recognizable faults, the FLVF must accommodate as much as half of the extensional
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deformation within the northern ECSZ.
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In this paper, we report new observations from our analysis of light detection and ranging
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(LiDAR) data, as well as terrestrial cosmogenic nuclide (TCN) dating of faulted land forms
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along the Fish Lake Valley fault. Our results provide new, geochronologically- determined, late
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Pleistocene-Holocene extension rates on this fault system that bear on how motion in the ECSZ
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is accommodated, and ultimately transferred northward to the Walker Lane.
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DEATH VALLEY-FISH LAKE VALLEY FAULT ZONE
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The Fish Lake Valley fault, which forms the northern 80 km of the Death Valley-Fish
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Lake Valley fault system, is marked by steep, east-facing fault scarps, ponded drainages, and
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shutter ridges indicative of recent fault activity (Brogan et al., 1991; Reheis, 1992; Reheis et al.,
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1993; Reheis et al., 1995; Frankel et al., 2007a, b). The southern and central sections of the
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FLVF strike predominantly northwest, whereas the northern part of the fault is characterized by
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numerous north-striking strands that splay out into Fish Lake Valley from the main range-
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bounding fault (Fig. 2; Sawyer, 1991; Reheis and Sawyer, 1997) .
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Based on differences in fault strike and fault scarp morphology, Brogan et al. (1991) and
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Sawyer (1990, 1991) separated the FLVF into four sections. From south to north these are the
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Cucomongo Canyon, Oasis, Dyer, and Chiatovitch Creek sectons. Right-lateral motion on the
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Fish Lake Valley fault is thought to have begun ~10 Ma ago (Reheis and Sawyer, 1997), and the
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strike-slip rate averaged over late Pleistocene-Holocene time is 2.5 to 3 mm/yr (Frankel et al.,
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2007b). The extensional component of oblique normal-dextral motion, responsible for the
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opening of Fish Lake Valley, most likely began ~ 5 Ma ago, as suggested by the observations
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that the bounding faults in the northern section of the valley cut across sedimentary rocks of the
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Miocene Esmeralda basin (Reheis and Sawyer, 1997). On the west side of the White Mountains,
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the right-lateral White Mountains fault originated later, at ~3 Ma (Stockli et al., 2003); the late
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Pleistocene-Holocene White Mountains fault oblique-slip rate is ~0.9 mm/yr parallel to a net
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slip vector plunging ~20° toward 340°-350° (Kirby et al., 2006).
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The focus areas of our study are normal fault scarps formed in four alluvial fans along
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the Chiatovich Creek, Dyer, and Oasis sections of the fault, which have been extensively mapped
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by a number of researchers (Fig. 2; Brogan et al., 1991; Reheis, 1992; Reheis et al., 1993 and
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1995). These four alluvial fans are deposited along the eastern White Mountains piedmont at the
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mouths of (from south to north) Furnace Creek, Wildhorse Creek, Perry Aiken Creek, and Indian
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Creek. We refer to each of our study sites relative to the respective creek that formed them. At
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two of the sites, Furnace Creek and Indian Creek, the fault zone exhibits predominantly right-
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lateral strike slip, with large (180-290 m) dextral offsets. Using cosmogenic 10Be surface
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exposure geochronology, Frankel et al. (2007b) determined the ages of the offset surfaces (unit
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Qfi of Reheis et al., 19XX) to be ~94 ka for Furnace Creek and ~71 ka for Indian Creek; the
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resulting right-lateral strike-slip rates at these two locations are 3.1 ± 0.4 mm and 2.5 ± 0.4
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mm/yr, respectively. Multiple normal-fault scarps are also present in both of these alluvial fans,
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as we discuss below.
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Our other two study sites, Wildhorse Creek and Perry Aiken Creek, are located between
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the Furnace Creek and Indian Creek fans (Fig. 1). Both the Wildhorse Creek and Perry Aiken
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Creek sites have numerous fault scarps cutting the alluvium with a predominantly normal
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component of slip. The highest single normal-fault scarp (minimum vertical displacement of ~85
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m) along the entire Death Valley-Fish Lake Valley fault zone is found just north of Perry Aiken
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Creek (Reheis and Sawyer, 1997). Reheis (1993) used tephrochronology to suggest that alluvial
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fans at Wildhorse Creek and Perry Aiken Creek were deposited during middle to late Pleistocene
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time.
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GEOMORPHIC ANALYSIS OF NORMAL FAULT SCARPS
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The analysis of LiDAR digital topographic data is an integral component of our study.
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The LiDAR data were collected in the Fall of 2005 by the National Center for Airborne Laser
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Mapping (NCALM) using an Optech Inc. Model ALTM 2033 laser mapping system. The laser
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was installed on a Cessna 337 twin engine aircraft, which flew over the fault trace at an average
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elevation of 600 m above ground level and an average speed of 60 m/s. The pulse rate frequency
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of the Optech ALTM 2033 was set at 33 KHz and it recorded the first and last returns of each
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pulse, plus the relative intensity of each return. The average shot density for the LiDAR data was
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~3 points/m2. The aircraft was equipped with a dual-frequency GPS receiver and a real-time
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display of the flight path and area coverage. High-resolution digital elevation models (DEMs)
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with 5-10 cm vertical accuracy and 1 m horizontal resolution were produced using a kriging
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algorithm in SURFER software (Version 8.04; Carter et al., 2007; Sartori, 2005).
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ArcGIS (Version 9.2) was used to produce hill-shaded relief maps to aid in the
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identification and mapping of all normal fault scarps at each site. We analyzed a total of 27
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profiles perpendicular to the strike of each set of scarps and measured the mean vertical
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component of displacement (Figs. 3-7, Table 1; please also see Data Repository item 1). The
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profiles were collected across fault scarps formed in unconsolidated alluvium where material is
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transported down-scarp by rain splash and gravity-driven soil creep; it is assumed that material is
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not transported in or out of the profile (e.g., Hanks et al., 1984; McCalpin, 1996; Arrowsmith et
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al., 1998). Maximum vertical components of displacement of the alluvial surfaces were
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calculated geometrically using the middle of the fault scarp (Fig. 8; Hanks et al., 1984). The
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horizontal component of each displacement was subsequently calculated using simple
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trigonometric relationships by assuming a 60º dip of the fault plane for each scarp (e.g., Kirby et
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al., 2006; Le et al., 2007; Lee et al., 2009). Uncertainties associated with measurements of the
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vertical components of each displacement include surface roughness (~20 cm) and the vertical
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accuracy (~10 cm) of the LiDAR data (e.g., Le et al., 2006). Combined, these two uncertainties
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are <5% of the total mean vertical component of displacement at each site and thus we report a
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conservative displacement error of 5%. We report the horizontal (extensional) component of
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displacement across the fault zone at each of the four sites, rather than the total vertical
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separation, due to the presence of multiple scarps associated with antithetic faults, which would
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lead to a reduction in the net vertical displacement across the fault zone; we feel that the total
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extension represents a more robust measure of the net fault slip.
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Furnace Creek
Two fault sets are prominent at the Furnace Creek site: north-northwest trending faults of
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the main, predominantly right-lateral strand of the FLVF, and a northeast-trending set of
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distributed normal faults to the east (Fig. 3A). The northeast-trending set of distributed faults
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accommodate slip that is not directly related to the extension on the FLVF, and we therefore
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analyzed eight profiles across the scarps of the main, predominantly right-lateral fault strand at
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the Furnace Creek site (Figs. 3A and 4). Transects PP’-P1P1’ and QQ’-Q1Q1’ are superimposed in
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order to capture the vertical component of displacement across the right-laterally offset alluvial
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fan. Inasmuch as right-lateral offset of the alluvial fan at this location will result in an apparently
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smaller scarp height, these profiles provide us with the minimum vertical displacement. Profiles
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RR’ through WW’ also record the vertical component of fault offset across a strand with
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predominantly right-lateral slip, and therefore the cumulative mean horizontal displacement
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measured at Furnace Creek is 8.3 ± 0.4 m (Fig. X).
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Wildhorse Creek
The two profiles (NN’ and OO’) we analyzed at Wild Horse Creek were oriented to most
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effectively capture all five of the main identifiable fault scarps (Figs. 3B and 5). Although some
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of the scarps face east and others face west, which would lead to a reduction in the net vertical
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displacement across the fault zone, it does not affect our calculations in terms of horizontal
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displacement. Although there is evidence for right-lateral slip at this site (e.g., the shutter ridge to
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the south of the active channel) no measurable offset markers are present. The cumulative mean
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horizontal displacement at Wildhorse Creek is 19.9 ± 1.0 m (Fig. X).
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Perry Aiken Creek
We used four transects, JJ’ through MM’, to measure the cumulative displacement at the
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Perry Aiken Creek site (Figs. 3C and 6). The vertical component of total displacement (85m) at
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this site is in agreement with previous measurements by Reheis and Sawyer (1997), who
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suggested ~85 m. Similar to the Wildhorse Creek site, although evidence for right-lateral
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component of slip is recognizable (e.g., the deflected canyon and abandoned channel at alluvial
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fan head), no measurable dextral offset markers are present. The cumulative mean horizontal
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component of displacement at Perry Aiken Creek is 49.1 ± 2.5 m.
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Indian Creek
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At the Indian Creek site we analyzed nine topographic profiles across three different sets
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of fault scarps (Figs. 3D and 7). Profile AA’ extends across the two normal-fault scarps, one
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facing east and one facing west, to the west of the range-front dextral fault strand. We used
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profile BB’ to capture the horizontal displacement across the main right-lateral strand of the
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fault. Profiles CC’ through II’ were used to measure the displacement across a set of distributed,
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north-northeast-trending normal faults to the east. The vertical displacement (~75 m) at this site
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is larger than the previously reported preferred vertical component of displacement of 40 m by
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Reheis and Sawyer (1997). Our preferred cumulative mean horizontal displacement at Indian
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Creek is 43.7 ± 2.1 m.
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TERRESTRIAL COSMOGENIC NUCLIDE GEOCHRONOLOGY
We used terrestrial cosmogenic nuclide geochronology (TCN) to date the offset alluvial
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fans along the FLVF. TCN geochronology allows for the determination of the age of
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abandonment of an alluvial surface (e.g., Gosse and Phillips, 2001). When combined with
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measured displacements across normal fault scarps, ages of the offset landforms can yield rates
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of deformation. TCN geochronolgy measures the concentration of nuclides produced in a rock by
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the interaction between cosmic rays and minerals at the Earth’s surface (e.g., Lal, 1991; Gosse
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and Phillips, 2001). In order to obtain plausible results, several criteria must be satisfied: (1) the
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sampled boulder must be in the same geometry as it was at the time of deposition; (2) the
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sampled boulder should not have prior exposure history (inheritance); and (3) boulders with
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evidence of erosion should not be sampled since they will provide an attenuated concentration of
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cosmogenic isotopes and hence, an apparently young age (Gosse and Phillips, 2001).
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The isotope of interest for this study is 10Be, which is produced through spallation and
muon-induced reactions with Si and O in quartz. Beryllium-10 is well-retained in quartz minerals
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which we collected from granitic boulders embedded in the surface of the offset alluvial fans.
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Fifteen samples were collected from the top 1 to 5 cm of large granitic boulders (Table 1). These
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boulders came from the stable parts of fan surfaces mapped by Reheis et al. (1993, 1995) as Qfm
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at Wildhorse Creek and Qfi at Perry Aiken Creek (Fig. 9). We carefully selected well-varnished
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boulders that lack evidence of erosion (e.g., “sombrero–shaped” boulders).
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Quartz was purified by standard techniques and Be was extracted using ion-exchange
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chromatography, precipitated as BeOH, and converted to BeO at the Georgia Institute of
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Technology cosmogenic nuclide geochronology laboratory (e.g., Kohl and Nishiizumi, 1992;
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Bierman et al., 2002). The 10Be/9Be ratio for each sample was measured at the Center for
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Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory and model 10Be
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ages were calculated using the CRONUS-Earth 10Be-26Al exposure age calculator (version 2.0;
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http://hess.washington.edu/math) and constant 10Be production rates (Lal, 1991; Stone, 2000;
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Balco et al., 2008).
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Wildhorse Creek Fan Age
We analyzed six TCN samples collected from the Qfm alluvial fan surface at Wildhorse
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Creek. The Qfm surface is characterized by subdued to moderately-incised channels, well-
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developed desert pavement, and a continuous, thick desert varnish on clasts. Furthermore, Qfm
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exhibits a thick silty vesicular A horizon, strong argillic B horizon, and stage IV laminar
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carbonate development (e.g., Reheis and Sawyer, 1997). Samples from this surface range in age
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from 100 ± 9 ka to 139 ± 13 ka, forming a tight cluster at ~120 ka (Fig. 10A). The mean age and
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standard deviation of these dates is 121 ± 14 ka. We take the clustered distribution of these
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samples as evidence that the Qfm surface has remained relatively stable since the time of
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deposition and that inheritance is minimal.
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Perry Aiken Creek Fan Age
Nine TCN samples were analyzed from the Qfi alluvial fan surface at Perry Aiken Creek.
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The Qfi surface is characterized by subdued to moderately-incised channels, well-developed
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desert pavement, and a continuous, thick desert varnish on clasts. In addition, Qfi is
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distinguished by a well-developed soil with a 5-to-10-cm-thick silty vesicular A horizon, a weak
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argillic B horizon with thin clay films and a stage II to III carbonate development (e.g., Reheis
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and Sawyer, 1997). Our Qfi ages, like the ages from Wildhorse Creek, exhibit a pronounced,
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single peak distribution with a mean age and standard deviation of 71± 8 ka (Fig. 10B). The
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range of ages varies from 54 ± 5 ka to 79 ± 7 ka. As with the Wildhorse Creek samples, we take
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the tight cluster of ages as an indication that the Qfi surface has remained relatively stable and
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that there is negligible inheritance. The age we obtained for Qfi at Perry Aiken Creek is in close
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agreement with the previously determined 10Be age of 71 ± 8 ka for the Qfi deposit at Indian
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Creek by Frankel et al. (2007b), and the 50-130 ka age estimated by Reheis and Sawyer (1997)
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on the basis of soil development and surface morphology.
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Furnace Creek and Indian Creek Fan Ages
The ages of the alluvial fans at Furnace Creek and Indian Creek were recently determined
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by Frankel et al. (2007b) using cosmogenic 10Be geochronology, and we utilize their results to
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determine the extension rates at these two locations. At Furnace Creek, Frankel et al. (2007b)
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report an age for surface Qfio (modified from Qfi of Reheis and Sawyer, 1997) of 94 ± 11 ka,
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while at Indian Creek they determined the age of surface Qfiy (modified from Qfi of Reheis and
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Sawyer, 1997) to be 71 ± 8 ka. Both of these ages are in agreement with previously reported soil
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and fan morphology data from those sites by Reheis and Sawyer (1997).
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Summary of Rate Data Along the Fish Lake Valley Fault
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We calculate extension rates at each of our four study sites by combing vertical
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components of displacement, fan surface ages, and an assumed 60° fault dip. Specifically, our
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extension rates are computed by combining probability density functions of the measured
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displacements and TCN ages and employing a Gaussian uncertainty model (e.g., Bird, 2007;
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McGill et al., 2009; Zechar and Frankel, in review). Uncertainties in the extension rates are
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reported at the 2σ confidence interval. The resulting east-west extension rates from south to north
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are: Furnace Creek = 0.1 ± 0.1 mm/yr, Wildhorse Creek = 0.2 ± 0.1 mm/yr, Perry Aiken Creek =
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0.7 +0.3/-0.1 mm/yr, and Indian Creek = 0.6 +0.2/-0.1 mm/yr. The 10Be dates from all four of
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our sites should be considered maximum ages for calculating the extension rates because the
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normal fault scarps must have developed after the deposition and abandonment of the Qfi and
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Qfm alluvial fan deposits. Moreover, although we are confident that we have captured all of the
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main fault strands that exhibit a normal component of slip, some distributed deformation that
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does not manifest itself as generally recognizable fault scarps could be present. Furthermore,,
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decreasing the assumed dip angle of 60º for the fault planes would also increase the calculated
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rates of extension. Thus, the combination of the maximum TCN ages, minimum displacements,
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and the assumed fault dip yield minimum extension rates.
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DISCUSSION
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The new rate data described above allow us to place constraints on the style and location
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of strain transfer from faults of the ECSZ to structures in the Walker Lane through the Mina
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Deflection. The extension rates we obtain on the FLVF increase northward from 0.1 +/- 0.1
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mm/yr and 0.2 +/- 0.1 mm/yr at Furnace Creek and Wildhorse Creek,, to 0.7 +0.3/-0.1 m/yr and
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0.6 +0.2/-0.1 mm/yr at the Perry Aiken Creek and Indian Creek. These extension rates are
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similar to those estimated by Reheis and Sawyer (1997), who reported a preferred late-
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Pleistocene vertical component of oblique slip at Furnace Creek of 0.3 mm/yr and 0.8 mm/yr at
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Indian Creek, on the basis of tephrochronology. If we assume a 60º dip for the fault plane, their
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preferred extension rates at Furnace Creek and Indian Creek are 0.2 mm/yr and 0.5 mm/yr,
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respectively. No preferred vertical component of total slip rate was reported by Reheis and
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Sawyer (1997) for Wildhorse Creek and Perry Aiken Creek.
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Geodetic vs. Geologic Rates of Extension
If the present-day extension rate of ~1 mm/yr determined by GPS (Bennett et al., 2003;
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Wesnousky, 2005a) has remained constant over Holocene to late Pleistocene timescales at the
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latitude of Fish Lake Valley, then approximately half of this regional extension must be
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accommodated by the northern FLVF. The remaining extensional deformation appears to be
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taken up by faults to the west, including the White Mountains fault (Kirby et al., 2006),
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distributed normal faulting in the Volcanic Tablelands (Kirby et al., 2006; Greene et al., 2007;
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data of Greene and Kirby in Frankel et al., 2008a), and the Sierra Nevada frontal fault system (Le
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et al., 2006), including the Round Valley and Hilton Creek faults north of Owens Valley (Fig.
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11; Berry et al., 1997) . The oblique-normal-dextral White Mountains fault exhibits a late
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Pleistocene extension rate at the latitude of our Furnace Creek site of ~0.2 mm/yr (Kirby et al.,
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2006), while at approximately the same latitude there is clear evidence for distributed normal
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faulting across the Volcanic Tablelands (e.g., Sheehanand Dawers, 2005; Pinter and Keller,
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1995). Further west at the same latitude Berry (1997) reports a 0.5-0.6 mm/yr late Pleistocene
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vertical component of slip on the Round Valley fault. This is equivalent to an extension rate on a
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60° dipping fault of ~0.3 mm/yr. Therefore, by combining all known extension rate data from
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these faults of the northern ECSZ we can account for nearly all of the geodetically-determined
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extension deformation at the latitude of central/northern Fish Lake Valley.
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Strain Transfer at the ECSZ-Walker Lane Transition
Recent work by Frankel et al. (2007b) at Furnace Creek and Indian Creek determined the
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late-Pleistocene right-lateral slip rate of the FLVF oblique system. The reported slip rates of 3.1
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± 0.4 mm/yr at Furnace Creek and 2.5 ± 0.4 mm/yr at Indian Creek, suggest an apparent
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northward decrease in dextral motion along the FLVF. The northward decrease in right-lateral
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slip rate is even more pronounced in the northern-most part of Fish Lake Valley, where the
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surface expression of the fault zone ends abruptly less than ~15 km north of Indian Creek.
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The observation that extension rates increase northward along the FLVF while dextral
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rates decrease has important implications for the distribution of strain along this section of the
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Pacific-North America plate boundary and, more generally, for mechanisms of slip transfer along
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evolving, structurally complex fault systems (Fig. 11). The FLVF system ends just north of
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Indian Creek and slip is transferred northeastward across the Mina Deflection onto oblique
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normal-right-lateral faults of the Walker Lane belt. Thus, the Mina Deflection can be thought of
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as a major right step (~80 km wide) in a dominant right-lateral fault system (e.g., Oldow et al.,
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1994, 2001; Wesnousky, 2005a; Petronis et al., 2002; Petronis, 2005). Within the Mina
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Deflection deformation is accommodated by left-lateral faults and clockwise block rotations
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(Wesnousky, 2005a).In general, both the northward increase in extension that we document, and
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the northward decrease in dextral slip documented by Frankel et al. (2007b) reflect transfer of
333
slip off the predominantly right-lateral FLVF onto north- and northeast-trending normal faults as
334
part of a distributed zone of slip transfer between the Emigrant Peak fault and the east-west-
335
trending left-lateral faults of the Mina Deflection. For example, the north-northeast-trending
336
normal faults that cut the fan to the east of the main range front fault strands at the Furnace
337
Creek site appear to “pull” slip off the FLVF system and transfer it northeastward onto the
338
Emigrant Peak fault system (Figure ?). Similarly, the north-northeast-trending normal faults at
339
Indian Creek serve to transfer slip off the FLVF and into the zone of distributed normal faulting
340
in this corner of Fish Lake Valley, leaving only 2.5 mm/yr of right-lateral strike-slip motion on
341
the FLVF at this site (Fig. X; Frankel et al., 2007b). This diffuse normal faulting, together with
342
normal displacements on the prominent Emigrant Peak fault system, account for the
343
development of the deep basin that defines the northeast-trending part of northern Fish Lake
344
Valley (including the dry ‘Fish Lake”, proper). However, the most pronounced decrease in right-
345
lateral strike-slip rate along the FLVF occurs just north of the Indian Creek site, where the
346
geomorphic expression of the fault system dies out completely within a zone of extensive recent
347
lava flows inthe Volcanic Hills (Fig. 11). Thus, between the north end of the geomorphically
348
well-defined FLVF at Indian Creek, and the left-lateral faults of the Mina deflection to the north,
349
it appears that distributed down-to-the-northwest normal faulting may accommodate as much as
350
2.5 mm/yr of dextral motion (e.g., Frankel et al., 2007b). The coincidence of this zone of
351
apparent distributed normal faulting and the extensive volcanism in the Volcanic Hills suggests
352
that the volcanism may be localized by this slip transfer zone.
Ganev et al., 2009
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353
Ultimately, at least some of this motion is must be accommodated along the east-west-
354
trending left-lateral faults of the Mina Deflection (Fig. 1; the Coaldale, Excelsior Mountains, and
355
Rattlesnake Flat faults). For example, the Coaldale fault, which has a minimum late Pliocene
356
sinistral slip rate of ~0.3-0.4 mm/yr (Lee et al., 2006) could potentially accommodate some of
357
the east-west extension that we observe in the northern part of Fish Lake Valley. But, the manner
358
in which this slip transfers northward onto the left-lateral faults remains unclear, as the there are
359
no geomorphically well-expressed faults in the 15-km-wide zone between the northern end of the
360
FLVF and the Coaldale fault (Fig. X). If, as we suspect, this slip is transferred northward into the
361
Mina Deflection along a diffuse set of highly distributed normal faults beneath the Volcanic
362
Hills, then this would imply that either clockwise rotations and/or left-lateral slip rates on the
363
Mina Deflection faults would increase to the east.
364
One possibility that we consider is that the northeast-trending normal faults that
365
characterize the northern part of Fish Lake Valley represent an early stage in the evolution of
366
faults similar to the Coaldale fault. In such a scenario, these faults would develop as northeast-
367
trending normal faults that act to transfer strain across the major right step of the Mina
368
Deflection. In response to ongoing right-lateral shear, these northeast-trending normal faults
369
would gradually rotate clockwise into a more east-west orientation, switching to left-lateral
370
strike-slip structures as a result of this reorientation. However, the well-established nature of the
371
northeast-trending basin along the north side of the Silver Peak Range, and long-term activity of
372
the north- to northeast-trending Emigrant Peak fault system (Petronis et al., 2002; Petronis, 2005)
373
argue that these are well-established, long-lived features that do not appear to be actively
374
rotating. In either case , slip transfer across the northern end of Fish Lake Valley into and across
375
the Mina Deflection appears to involve a large component of distributed normal faulting, as well
Ganev et al., 2009
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376
as left-lateral strike-slip faulting, perhaps quite distributed at the northwest corner of the valley,
377
and clockwise rotations (Fig. 12).
378
379
380
CONCLUSIONS
New LiDAR topographic data and cosmogenic 10Be geochronology of offset alluvial fan
381
deposits on the dextral-oblique Fish Lake Valley fault yield well-determined late Pleistocene-
382
Holocene extension rates on this major oblique normal-dextral fault system. The surface
383
exposure ages of four sites, Furnace Creek, Wildhorse Creek, Perry Aiken Creek, and Indian
384
Creek (from south to north) range from ~71 ka to ~121 ka, and the mean horizontal extensional
385
components of displacement at these sites range from ~8 m to ~49 m. By combining probability
386
density functions of these displacements and ages, we find that extension rates averaged over late
387
Pleistocene-Holocene time vary from 0.1 mm/yr at Furnace Creek and 0.2 mm/yr at Wildhorse
388
Creek in the south, to 0.7 and 0.6 mm/yr at Perry Aiken Creek and Indian Creek, respectively, to
389
the north.
390
These rate suggest that the FLVF accommodates approximately half of the region-wide
391
geodetic rate of extension. When summed with extension rates along the western White
392
Mountains piedmont, the Sierra Nevada frontal fault, and distributed deformation across the
393
Volcanic Tablelands, the long-term geologic rates of extension are commensurate with the short-
394
term rates determined from GPS data.
395
The increase in the east-west extensional component of slip towards the northern end of
396
the ECSZ reflects a gradual northeastward transfer of slip off the predominantly right-lateral
397
FLVF and across the Mina Deflection as part of a distributed zone of north-east-trending normal
398
faulting. Further north, in the Mina Deflection proper, deformation is accommodated
Ganev et al., 2009
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399
predominantly by the presence of east-west oriented left-lateral faults. Collectively, the
400
distributed normal faulting in northern Fish Lake Valley, together clockwise rotations and
401
motion on the east-west left-lateral faults of the Mina Deflection, serve to transfer deformation
402
through this major right-step in the eastern California shear-zone-Walker Lane belt.
403
404
405
ACKNOWLEDGEMENTS
We thank Dylan Rood and Alicia Nobles for assistance with sample preparation and
406
analysis, and Trevor Thomas for his assistance in the field. XXXXXXXXX and XXXXXXXXX
407
provided thoughtful reviews that significantly improved the manuscript. The LiDAR data were
408
collected by the National Center for Airborne Laser Mapping, and we are indebted to Michael
409
Sartori and Ionut Iordache for help with data processing. This research was made possible by the
410
support of NSF grants EAR-0537901 and EAR-0538009, a NASA Earth System Science
411
Fellowship, and the Georgia Tech Research Foundation
412
413
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Figure captions
623
Figure 1: Hillshaded relief map and Quaternary faults in the northern ECSZ. Fish Lake Valley
624
fault is shown in white. The corners of Figure 2 are shown in black. Faults are from the USGS
625
Quaternary fault and fold database. AHF- Ash Hill fault, ALF- Airport Lake fault, BSF- Benton
626
Springs fault, CF- Coaldale fault, EF- Excelsior Mountains fault, EPF- Emigrant Peak fault,
627
EVF- Eureka Valley fault, DSF- Deep Springs fault, FLVF- Fish Lake Valley fault, GF- Garlock
628
fault, HCF- Hilton Creek fault, HMSVF- Hunter Mountain-Saline Valley fault, LMF- Lone
629
Mountain fault, MLF- Mono Lake fault, NDVF- northern Death Valley fault, OVF- Owens
630
Valley fault, PSF- Petrified Springs fault, PVF- Panamint Valley fault, QVF- Queen Valley fault,
631
RF- Rattlesnake Flat fault, RVF- Round Valley fault, SLF-Silver Lake fault, SNF- Sierra Nevada
632
frontal fault, SVF- Saline Valley fault, TMF- Tin Mountain fault, TPF- Towne Pass fault, WF-
633
Warm Springs fault, WMF- White Mountains fault. GPS strain accumulation rates from Bennett
634
et al. (2003).
635
Ganev et al., 2009
Page 23
636
Figure 2: Detailed index map of the study area. The locations of study sites are labeled 1 through
637
4 from south to north: 1- Furnace Creek; 2- Wildhorse Creek; 3- Perry Aiken Creek; 4- Indian
638
Creek. DSF- Deep Springs fault, EPF- Emigrant Peak fault, FLVF- Fish Lake Valley fault, OVF-
639
Owens Valley fault, QVF- Queen Valley fault; WMF- White Mountains fault.
640
641
Figure 3: Selected topographic profiles across alluvial fan surfaces and calculated vertical
642
components of displacement from the four study sites: (a) Furnace Creek; (b) Wildhorse Creek;
643
(c) Perry Aiken Creek; (d) Indian Creek. See Figures 4-7 for profile locations.
644
645
Figure 4: Hillshaded LiDAR-derived DEM of the Furnace Creek site showing the topographic
646
profiles analyzed. The number by each fault scarp corresponds to the fault number in Table 1.
647
The mapped Quaternary surfaces are modified from Reheis et al. (1993). See Table 1 for the
648
detailed measurements of scarp heights.
649
650
Figure 5: Hillshaded LiDAR-derived DEM of the Wildhorse Creek site showing the topographic
651
profiles analyzed. The green dots indicate the locations of the dated samples. The number by
652
each fault scarp corresponds to the fault number in Table 1. The mapped Quaternary surfaces are
653
modified from Reheis et al. (1993). See Table 1 for the detailed measurements of scarp heights.
654
655
Figure 6: Hillshaded LiDAR-derived DEM of the Perry Aiken Creek site showing the
656
topographic profiles analyzed. The green dots indicate the locations of the dated samples. The
657
number by each fault scarp corresponds to the fault number in Table 1. The mapped Quaternary
Ganev et al., 2009
Page 24
658
surfaces are modified from Reheis et al. (1993). See Table 1 for the detailed measurements of
659
scarp heights.
660
661
Figure 7: Hillshaded LiDAR-derived DEM of the Indian Creek site showing the topographic
662
profiles analyzed. The number by each fault scarp corresponds to the fault number in Table 1.
663
The mapped Quaternary surfaces are modified from Reheis et al. (1995). See Table 1 for the
664
detailed measurements of scarp heights.
665
666
Figure 8: Geometry of an ideal fault scarp, after Hanks et al. (1984). S- surface offset or scarp
667
offset; 2H- scarp height; θf- far-field slope angle; θs- scarp slope angle.
668
669
Figure 9: Representative examples of sampled boulders from (a) the Qfm deposit at Wildhorse
670
Creek, and (b) the Qfi deposit at Perry Aiken Creek.
671
672
Figure 10: Probability density functions of the 10Be ages from surface boulders. (a) Probability
673
density function of the six samples used to determine the age of Qfm at Wildhorse Creek. (b)
674
Probability density function of the nine samples used to determine the age of Qfi at Perry Aiken
675
Creek. The uncertainties are reported as the mean and standard deviation.
676
677
Figure 11: Rates of extension on faults in the ECSZ between 37° N and 38° N latitude. The rates
678
on the Round Valley fault (RVF) and Hilton Creek fault (HCF) are from Berry (1997), the rate
679
in the Volcanic Tablelands is determined by Sheehan, T. and Dawers, N. (2005), the rate on the
680
White Mountains fault (WMF) is from Kirby et al. (2006), and the rates on the FLVF are from
Ganev et al., 2009
Page 25
681
this study. In some of the aforementioned publications the authors report only the vertical
682
component of slip; therefore, we resolve the extension rates by assuming a 60° fault dip on the
683
faults. DSF- Deep Springs fault, EPF- Emigrant Peak fault, FLVF- Fish Lake Valley fault, HCF-
684
Hill Creek fault, OVF- Owens Valley fault, QVF- Queen Valley fault, RVF- Round Valley fault.
685
686
Figure 12: Fault model showing the development of northeast-striking normal faults transferring
687
strain in a right stepover between two northwest-striking zones of right-lateral shear. Clockwise
688
rotation of the normal faults is necessary to achieve the highest efficiency in slip transfer. Along
689
the FLVF the right-lateral slip rate decreases northward near the Mina Deflection where there is
690
an increase in the extension rate of the fault zone. These observations suggest the possible
691
development of a nascent strain transfer system between the northern ECSZ and Walker Lane.
692
693
Tables
694
Table 1: Measured vertical and calculated horizontal offsets from profiles.
695
696
Table 2: Analytical results of terrestrial cosmogenic nuclide 10Be geochronology for the
697
Wildhorse Creek and Perry Aiken Creek alluvial fans in Fish Lake Valley.
698
699
Data Repository Figure Caption
700
Figure DR1: Complete list of the analyzed topographic profiles across alluvial fan surfaces and
701
calculated vertical components of displacement from the four study sites: (a) Furnace Creek; (b)
702
Wildhorse Creek; (c) Perry Aiken Creek; (d) Indian Creek. See Figures 4-7 for locations of the
703
profiles.
Ganev et al., 2009
Page 26
704
705
Figures
706
Figure 1: Topographic map and Quaternary faults in the northern ECSZ. Fish Lake Valley fault
707
is shown in white. The corners of Figure 2 are shown in black. Faults are from the USGS
708
Quaternary fault and fold database. AHF- Ash Hill fault, ALF- Airport Lake fault, BSF- Benton
709
Springs fault, CF- Coaldale fault, EF- Excelsior Mountains fault, EPF- Emigrant Peak fault,
710
EVF- Eureka Valley fault, DSF- Deep Springs fault, FLVF- Fish Lake Valley fault, GF- Garlock
711
fault, HCF- Hilton Creek fault, HMSVF- Hunter Mountain-Saline Valley fault, LMF- Lone
712
Mountain fault, MLF- Mono Lake fault, NDVF- northern Death Valley fault, OVF- Owens
713
Valley fault, PSF- Petrified Springs fault, PVF- Panamint Valley fault, QVF- Queen Valley fault,
714
RF- Rattlesnake Flat fault, RVF- Round Valley fault, SLF-Silver Lake fault, SNF- Sierra Nevada
715
frontal fault, SVF- Saline Valley fault, TMF- Tin Mountain fault, TPF- Towne Pass fault, WF-
716
Warm Springs fault, WMF- White Mountains fault. GPS strain accumulation rates from Bennett
717
et al. [2003].
Ganev et al., 2009
Page 27
718
Ganev et al., 2009
Page 28
719
Figure 2: Detailed index map of the study area. The locations of our study sites are labeled 1
720
through 4 from south to north: 1- Furnace Creek; 2- Wildhorse Creek; 3- Perry Aiken Creek; 4-
721
Indian Creek. DSF- Deep Springs fault, EPF- Emigrant Peak fault, FLVF- Fish Lake Valley
722
fault, OVF- Owens Valley fault, QVF- Queen Valley fault; WMF- White Mountains fault.
723
724
Ganev et al., 2009
Page 29
725
Figure 3: Selected topographic profiles across alluvial fan surfaces and calculated vertical
726
components of displacement from the four study sites: (a) Furnace Creek; (b) Wildhorse Creek;
727
(c) Perry Aiken Creek; (d) Indian Creek. See Figures 4-7 for locations of the profiles.
728
Ganev et al., 2009
Page 30
729
Figure 4: Hillshaded LiDAR-derived DEM of the Furnace Creek site showing the topographic
730
profiles analyzed. The number by each fault scarp corresponds to the fault number in Table 1.
731
The mapped Quaternary surfaces are modified from Reheis et al. (1993). See Table 1 for the
732
detailed measurements of scarp heights.
733
734
735
736
737
Ganev et al., 2009
Page 31
738
Figure 5: Hillshaded LiDAR-derived DEM of the Wildhorse Creek site showing the topographic
739
profiles analyzed. The green dots indicate the locations of the dated samples. The number by
740
each fault scarp corresponds to the fault number in Table 1. The mapped Quaternary surfaces are
741
modified from Reheis et al. (1993). See Table 1 for the detailed measurements of scarp heights.
742
743
744
745
Ganev et al., 2009
Page 32
746
Figure 6: Hillshaded LiDAR-derived DEM of the Perry Aiken Creek site showing the
747
topographic profiles analyzed. The green dots indicate the locations of the dated samples. The
748
number by each fault scarp corresponds to the fault number in Table 1. The mapped Quaternary
749
surfaces are modified from Reheis et al. (1993). See Table 1 for the detailed measurements of
750
scarp heights.
751
752
753
754
Ganev et al., 2009
Page 33
755
Figure 7: Hillshaded LiDAR-derived DEM of the Indian Creek site showing the topographic
756
profiles analyzed. The number by each fault scarp corresponds to the fault number in Table 1.
757
The mapped Quaternary surfaces are modified from Reheis et al. (1995). See Table 1 for the
758
detailed measurements of scarp heights.
759
760
761
762
763
764
Ganev et al., 2009
Page 34
765
766
Figure 8: Geometry of an ideal fault scarp, after Hanks et al. (1984). S- surface offset or scarp
767
offset; 2H- scarp height; θf- far-field slope angle; θs- scarp slope angle.
768
769
770
771
772
Figure 9: Representative examples of sampled boulders from (a) the Qfm deposit at Wildhorse
773
Creek, and (b) the Qfi deposit at Perry Aiken Creek.
774
775
776
777
778
Ganev et al., 2009
Page 35
779
780
781
782
Figure 10: Probability density functions of the 10Be ages from surface boulders. (a) Probability
783
density function of the six samples used to determine the age of Qfm at Wildhorse Creek. (b)
784
Probability density function of the nine samples used to determine the age of Qfi at Perry Aiken
785
Creek. The uncertainties are reported as the mean and standard deviation.
786
787
788
789
790
791
792
793
Ganev et al., 2009
Page 36
794
795
796
797
Figure 11: Known rates of extension on faults in the ECSZ between 37° N and 38° N latitude.
798
The rates on the RVF and HCF are by Berry (1997), the rate in the Volcanic Tablelands is
799
determined by Sheehan, T. and Dawers, N. (2005), the rate on the WMF is published by Kirby et
800
al. (2006), and the rates on the FLVF are from this study. In some of the aforementioned
801
publications the authors report only the vertical component of slip; therefore, we resolve the
802
extension rates by assuming a 60° fault dip on the faults. DSF- Deep Springs fault, EPF-
803
Emigrant Peak fault, FLVF- Fish Lake Valley fault, HCF- Hill Creek fault, OVF- Owens Valley
804
fault, QVF- Queen Valley fault, RVF- Round Valley fault.
Ganev et al., 2009
Page 37
805
806
807
Figure 12: Fault model showing the development of northeast-striking normal faults transferring
808
strain in a right stepover between two northwest-striking zones of right-lateral shear. Clockwise
809
rotation of the normal faults is necessary to achieve the highest efficiency in slip transfer. Along
810
the FLVF the right-lateral slip rate decreases northward near the Mina Deflection where there is
811
an increase in the extension rate of the fault zone. These observations suggest the possible
812
development of a nascent strain transfer system between the northern ECSZ and Walker Lane.
Ganev et al., 2009
Page 38
813
814
815
816
817
818
819
Ganev et al., 2009
Page 39
820
TABLES
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
Ganev et al., 2009
Page 40
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
Ganev et al., 2009
Page 41
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
Ganev et al., 2009
Page 42
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
Data Repository Figure
911
Figure DR1: Complete list of the analyzed topographic profiles across alluvial fan surfaces and
912
calculated vertical components of displacement from the four study sites: (a) Furnace Creek; (b)
913
Wildhorse Creek; (c) Perry Aiken Creek; (d) Indian Creek. See Figures 4-7 for locations of the
914
profiles.
Ganev et al., 2009
Page 43
915
Ganev et al., 2009
Page 44
916
Ganev et al., 2009
Page 45
917
Ganev et al., 2009
Page 46
918
Ganev et al., 2009
Page 47
919
Ganev et al., 2009
Page 48
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