submitted to Geology 1

Late Quaternary slip rates along the Sierra Nevada frontal fault zone, California: Evidencefor slip partitioning across the western margin of the Eastern California Shear Zone/Basin

and Range ProvinceKimberly Le1, Jeffrey Lee

Department of Geological Sciences, Central Washington University, Ellensburg,Washington,98926, USA

Lewis A. OwenDepartment of Geology, University of Cincinnati, Cincinnati, Ohio 45221, USA

Robert FinkelCenter for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory,

Livermore, California 94550, USA

ABSTRACTNew geologic mapping, tectonic geomorphology, and cosmogenic radionuclide (CRN)

geochronology data provide the first quantitative rates on late Quaternary vertical slip andextension across the southern Sierra Nevada frontal fault zone, California. This fault zoneexposes numerous NNW-striking, east-facing normal fault scarps that offset seven distinctQuaternary alluvial fan surfaces (Qf1, Qf2a and b, Qf3a,b and c, and Qf4 – oldest toyoungest). Beryllium-10 CRN surface exposure dating of these surfaces provide surfaceabandonment ages of: 138 ± 35 ka for a Qf1 surface, 66 ± 16 ka for Qf2b, 23 ± 6 ka forQf3a, 5 ± 1.2 ka for Qf3c, and 4 ± 1 ka for Qf4. These ages combined with measurementsof vertical surface offset across fault scarps yield late Pleistocene vertical and horizontalslip rates of 0.2-0.4 ± 0.1 mm/yr and 0.1-0.3 ± 0.1 mm/yr, respectively, and Holocenevertical and horizontal slip rates of 1.4 ± 0.4 and 0.8 ± 0.2, respectively. These slip rateestimates are comparable to late Pleistocene vertical slip rate estimates across range frontnormal faults within the Basin and Range Province. The results, combined with data fromthe dextral Owens Valley fault, imply that the Sierra Nevada block is moving bothperpendicular and parallel to Pacific-North America plate motion.

INTRODUCTIONThe southwestern U.S. Cordillera is the world’s best place to examine the relative

contributions of plate boundary forces and internal driving forces to intracontinental deformationkinematics. One the most prominent geomorphic features within this region is the Sierra Nevada,a mountain range with a mean elevation of 2800 m above sea level and bounded along it’s eastflank by a normal fault system, the Sierra Nevada frontal fault zone (SNFFZ). The SNFFZdefines the western boundary of both the Eastern California Shear Zone and Basin and RangeProvince, a region where NW-dextral shear has been superimposed on EW-extension (Fig. 1).There is a long history of research on the origin Sierra Nevada topography and role the SNFFZplays in the evolution of this part of the Cordillera (e.g. Lindgren, 1911; Christensen, 1966).More recently, Flesch et al. (2000) used results from GPS, topographic, geoid, and Quaternaryfault slip studies to hypothesize that NW-dextral shear and EW-extension within the ECSZresulted from translation of the Sierra Nevada both parallel and perpendicular to the Pacific-North American plate boundary in consequence of plate tractions and gravitational potential

1 now at Department of Geological Sciences, California State University, Fullerton, California 92834, USA

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energy, respectively. Data from a number of studies investigating deformation over time scalesof ~3-8 Ma led Jones et al. (2004 and references therein) to suggest that removal of lithospherebeneath the Sierra Nevada at ~3.5 Ma initiated uplift and increased extensional strain rates. Theirproposal, invoking a combination of locally derived internal forces (gravitational potentialenergy) and plate boundary forces to drive fault kinematics along the western boundary of theEastern California Shear Zone and Basin and Range Province, is consistent with that of Flesch etal. (2000). In contrast to these hypotheses, the orientation of normal and strike-slip faults alongthe eastern margin of the Sierra Nevada relative to the small circles to the Sierra-Nevada-NorthAmerica Euler pole, coupled with kinematic inversions of earthquake focal mechanisms, ledUnruh et al., (2003) to hypothesize that normal faulting along the eastern flank of the SierraNevada is related to plate boundary driven NW-translation of this rigid block rather than toSierra Nevada uplift or regional Basin and Range extension. These geodynamic hypotheses makedifferent, testable predictions about the kinematics and rates of slip along the SNFFZ. Strainpartitioning, with normal slip along the SNFFZ and dextral slip elsewhere, and an increase in sliprate along the SNFFZ since the late Miocene to early Pliocene would support deformationkinematics driven by a combination of internal and external forces. In contrast, oblique slip(normal and right lateral) along the SNFFZ would support NW-translation of the Sierra Nevadasolely as a consequence of plate boundary forces.

In this paper, we describe the results of new detailed geologic mapping and cosmogenicradionuclide (CRN) geochronologic investigations along the southern part of the SNFFZ. Ourdata provide the first quantitative late Quaternary fault slip rates along this part of the SNFFZthat bear on the tectonic role of the Sierra Nevada during the late Quaternary.

GEOLOGIC SETTINGThe Sierra Nevada is a large, west-tilted normal fault-block that defines the western margin

of the Basin and Range Province in a region of active, intracontinental deformation where NW-dextral shear has been superimposed on EW-extension (Fig. 1). Today, this part of the margin isdominated by a complex array of NW-striking dextral faults, NE-striking connecting normalfaults, and NW-striking range bounding normal faults that define the Eastern California ShearZone (Dokka and Travis, 1990). This array of faults accommodates ~25% the relative motionbetween the Pacific and North American plates (e.g. Dixon et al., 2000; Gan et al., 2000).

The Sierra Nevada consists of Paleozoic and Mesozoic sedimentary and volcanic rocksintruded by Mesozoic granitic rocks overlain by Cenozoic volcanic and sedimentary deposits(e.g. Bateman and Wahrhaftig, 1966). The eastern piedmont of the southern Sierra Nevadacomprises extensive Quaternary alluvial fan, glacial, rockslide, and lacustrine deposits that arecut by normal faults. The SNFFZ forms the eastern escarpment of the Sierra Nevada and extends~300 km from just north of the Garlock fault to the Cascade Range.

SIERRA NEVADA FRONTAL FAULT ZONEAlluvial Fan Surfaces

The southern part of the SNFFZ, between Oak and Lubkin creeks, offsets granite- andmetamorphic-derived Quaternary coarse- to fine-grain alluvial fan, glacial, and rock slidedeposits (Figs. 2 and 3). Seven Quaternary alluvial fan surfaces of distinct ages have beenmapped based on alluvial fan surface morphology such as terrace height, presence or absence of

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bar and swale morphology, degree of fan dissection, desert pavement development, insetgeometry, and slope.

From oldest to youngest they are: Qf1—surface erosional remnants preserved as stronglydissected, high rounded mounds (30-100 m) with scarce, strongly weathered boulder clasts (Figs.2 and 3). Qf2a—surfaces characterized by ridge and ravine morphology and inset into Qf1surfaces. These are located a few meters to tens of meters above the modern channel.Qf2b—surfaces inset into Qf2a and relatively smooth to locally moderately dissected thatcontain large, moderately weathered, and embedded granitic boulders. Based on bar and swalemorphology, together with inset geometry, the next youngest surface, Qf3, is divided into threesubunits, Qf3a, b, and c. Qf3a—surfaces possess subdued bar and swale morphology, aremoderately dissected, and contain scarce large, fresh granitic boulders embedded in a matrix ofgranitic pebbles and sand. Qf3b—surfaces characterized by muted bar and swale morphology,channel incision 1.0-2.5 m deep, and large granitic boulders. Qf3c—surfaces are exposed at themouth of most creeks and canyons and extend ~2-4 km from the range front and preserve distinctbar and swale morphology containing boulder-lined channels and large (1-9 m) fresh graniticboulders. Qf4—the youngest surfaces are defined by channels that are active or have beenabandoned for a short period of time. These surfaces are typically densely vegetated and containunvarnished granitic clasts, debris flow deposits that include tree trunk clasts, and fresh boulderlevee bars.

Cosmogenic Radionuclide (CRN) Dating ResultsTwenty-eight quartz-rich granite samples were collected from the top of boulders for 10Be

CRN surface exposure age determination of five of the alluvial fan surfaces: Qf1, Qf2b, Qf3aand c, and Qf4.

Model 10Be ages for boulder samples collected from an offset Qf1 surface, located just southof Bairs Creek (Fig. 2), and from Qf2b, Qf3a and c, and Qf4 surfaces in the Symmes-Shepherdcreeks area (Fig. 3) yielded calculated surface abandonment ages of 138 ± 35.2 ka for Qf1, 66 ±16.0 ka for Qf2b, 23 ± 5.9 ka for Qf3a, 5 ± 1.2 ka for Qf3c, and 4 ± 1.1 ka for Qf4. These ageswere calculated with an erosion rate of 0.3 mm/yr of the boulder surface (Small et al., 1997).Ages in this study agree, within uncertainty, with published 10Be CRN surface abandonment ageselsewhere in the region (Bierman et al., 1995; Zehfuss et al., 2001). Results are summarized inTable 1, sample localities are shown in Figure 3, and dating procedures and sample descriptionsare in data repository 2005#####.

Fault Geometry, Magnitude of Offset, and Slip RatesThe ~35 km long stretch of the SNFFZ between Oak and Lubkin creeks is up to ~ 4 km wide

and is comprised of NNW-striking, dominantly E-dipping, but also W-dipping normal faultscarps. These scarps cut and offset Qf1, Qf2, and Qf3 surfaces, rockslides, and moraines, but notQf4 surfaces. Based on fault zone width, geometry, and location, this part of the SNFFZ definesfour distinct, right-stepping geometric segments (Fig. 2). Faults that define each segment have anaverage strike of ~N026W, whereas faults that define the step-over between segments strike~N010E. Segment A is a 4 km long and 4 km wide zone defined by six, sub-parallel, NW-striking, E-dipping normal faults. To the south of segment A, the locus of faulting steps ~1 km tothe west to segment B which is a 7 km long and 5 km wide zone dominated by as many as seven,NNW-striking, E- and W-dipping, sub-parallel, W-stepping en echelon normal faults. Segment

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C, located in the central part of the map area, is a ~10 km long and ~2 km wide zone of four sub-parallel, E-dipping en echelon normal faults. Faulting steps ~1 km westward to the south intosegment D which is a ~12 km long and ~2 km wide zone of NNW-striking, E-dipping normalfaults. Faults exposed in each segment exhibit normal, dip-slip motion; there is no geomorphicevidence for a lateral component of slip.

Kinematic GPS topographic profiling across normal fault scarps that cut and offset alluvialfan surfaces allow maximum vertical surface offsets to be determined (Table 1; Fig. 2).Combining data from 10Be CRN surface exposure dating with topographic profiling yieldsvertical slip rate estimates of 0.2-0.3 ± 0.1 mm/yr since ~138 ka, 0.2-0.3 ± 0.1 mm/yr since ~66ka, 0.4 ± 0.1 since ~23 ka, and 1.4 ± 0.4 since ~5 ka (Table 1). Assuming a fault dip of 60° yieldscalculated horizontal extension rates for the late Pleistocene to Holocene that range from 0.1-0.3± 0.1 mm/yr to 0.8 ± 0.2 mm/yr (Table 1). Our calculated vertical and horizontal slip rates of 1.4± 0.3 mm/yr and 0.8 ± 0.2 mm/yr, respectively, for the late Holocene are four to seven timesfaster than our late Pleistocene estimates (Table 1). This indicates either that horizontal extensionrates have increased over the last 5,000 years or that these calculated slip rates are maximabecause these faults are early in the earthquake cycle. The latter is our preferred interpretationand we suggest that the late Pleistocene vertical slip rate of 0.2-0.4 mm/yr remains constantthrough the Holocene.

DISCUSSION AND CONCLUSIONSOur new late Pleistocene and late Holocene vertical slip rate estimates of 0.2-0.4 ± 0.1 mm/yr

and 1.4 ± 0.3 mm/yr, respectively, are the first based on numerical ages for offset geologicmarkers along the SNFFZ. Our late Pleistocene CRN slip rate determinations are the same,within uncertainty, as geologic slip rates based on qualitative estimates of the age of offsetgeologic markers for the southern and central parts of the SNFFZ (Clark, 1972; Gillespie, 1982;Berry, 1989; Clark and Gillespie, 1993). For the Lone Pine fault, exposed ~10 km east of thefield area, offset measurements (Lubetkin and Clark, 1988; Beanland and Clark, 1994) and 10BeCRN model exposure ages of 11.6 ± 3.7 ka on granitic boulders from the offset surface (Biermanet al., 1995) yield a Holocene vertical slip rate of 0.5 ± 0.2 mm/yr, the same as our latePleistocene estimate. Likewise, for the Fish Springs fault, exposed to the NNE of our map area(Fig. 1), fault offset measurements and 10Be CRN model exposure ages on offset alluvial surfacesyielded a late Pleistocene vertical slip rate of ~0.2 mm/yr (Zehuss et al., 2001). Investigations ofuplifted river channels and deposits, volcanic flows, tilted strata, and river incision rates alongthe western flank of the Sierra Nevada suggest ~1.5 to 2.5 km of uplift during the past 3-5 Ma(Huber, 1981; Unruh, 1991; Wakabayashi and Sawyer, 2001; Stock et al., 2004), implying along-term vertical slip rate of ~0.3-0.8 mm/yr. This is the same, within error, as our latePleistocene vertical slip rate estimate. Our vertical slip rate estimates for the SNFFZ are also thesame as those estimated for several range bounding normal faults within the Basin and RangeProvince to the east (e.g. Wesnousky et al., in press; USGS, 2004; Friedrich et al., 2004; Haymanet al., 2003; Machette et al, 1992). If we assume that the SNFFZ and the Lone Pine fault dip 60°and 75°, respectively, then summing their late Pleistocene horizontal extension rates yields anestimated horizontal extension rate of 0.6 ± 0.2 mm/yr across Owens Valley at the latitude ofLone Pine. Shallower dipping faults will result in a higher rate of extension, whereas moresteeply dipping faults will result in a lower rate of extension.

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The SNFFZ, the Lone Pine fault, and the active Owens Valley fault, located ~15 km to theeast, form a normal-strike slip fault system with estimated normal and dextral slip rates of 0.6 ±0.2 mm/yr and 2 ± 1 mm/yr to 3.1 ± 0.7 mm/yr, respectively (Lubetkin and Clark, 1988;Beanland and Clark, 1992; Lee et al., 2001). These subparallel faults strike clockwise withrespect to the ~N047W-trending motion of the Sierra Nevada block relative to stable NorthAmerica (Dixon et al., 2000), yet only the Lone Pine fault exhibits oblique slip (Lubetkin andClark, 1988; Beanland and Clark, 1992; this study). These relations imply that motion of theSierra Nevada block is partitioned into three components—dominant dextral slip along theOwens Valley fault, intermediate oblique slip along the Lone Pine fault, and subordinate normalslip along the SNFFZ. This kinematic framework is consistent with the hypothesis that NW-dextral shear and EW-extension resulted from translation of the Sierra Nevada both parallel andperpendicular, respectively, to the Pacific-North American plate boundary as a consequence ofexternal and internal boundary forces (e.g. Hammond and Thatcher, 2004; Bennett et al., 2003;Flesch et al., 2000). This kinematic framework also indicates that plate boundary forcesdominate. Our short term slip rate estimates along the SNFFZ are the same, within error, withlonger term (Pliocene) estimates thus offering no support for an increase in extension rate sinceremoval of lithosphere beneath the Sierra Nevada at ~3.5 Ma as proposed by Jones et al. (2004).We speculate that extension rates either increased immediately following removal of denselithosphere, but soon thereafter slowed to rates similar to those observed across many normalfaults in the Basin and Range Province or that rates remained slow and constant in response toremoval of lithosphere. Variations in extensional strain rates, or lack thereof, along the SNFFZhave important implications for continental strength and viscosity of the asthenosphere.

ACKNOWLEDGMENTSThis research was supported by National Science Foundation grants EAR-0207365 and EAR-0207245, grants from Sigma Xi and the White Mountain Research Station awarded to K. Le, andwas performed under the auspices of the U.S. Department of Energy by the University ofCalifornia, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

REFERENCES CITEDBateman, P.C., and Wahrhaftig, C., 1966, Geology of the Sierra Nevada, in Bailey, E.H., ed.,

Geology of Northern California: California Division of Mines and Geology Bulletin, v. 190,p. 107-172.

Beanland, S., and Clark, M.M., 1994, The Owens Valley fault zone, eastern California, andsurface faulting associated with the 1872 earthquake: U.S. Geological Survey Bulletin 1982,29 p.

Berry, M.E., 1989, Soil-geomorphic analysis of late-Quaternary glaciation and faulting, easternescarpment of the central Sierra Nevada, California [Ph.D thesis]: Boulder, University ofColorado, 261 p.

Bennett, R., Wernicke, B., Niemi, N.A., Friedrich, A.M., Davis, J.L., 2003, Contemporary strainrates in the northern Basin and Range Province from GPS data: Tectonics, v. 22, p. 1-31.

Bierman, P.R., Gillespie, A.R., and Caffee, M.W., 1995, Cosmogenic ages for recurrenceintervals and debris flow fan deposition, Owens Valley, California: Science, v. 270, p 447-450.

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Christensen, M.N., 1966, Late Cenozoic crustal movements in the Sierra Nevada of California:Geological Society of America Bulletin, v. 77, p. 163-182.

Clark, D., 1972, Range-front faulting: cause of anomalous relations among moraines of theeastern slope of the Sierra Nevada, California: Geological Society of America Abstracts, p.137.

Clark, D., and Gillespie, A.R., 1993, Variations in late Quaternary behavior along and amongrange-front faults of the Sierra Nevada, California: Cordilleran and Rocky MountainSections, p. 21.

Dixon, T.H., Miller, M., Farina, F., Wang, H., and Johnson, D., 2000, Present-day motion of theSierra Nevada block, and some tectonic implications for the Basin and Range Province,North American Cordillera: Tectonics, v. 19, p. 1-24.

Dokka, R.K., and Travis, C.J., 1990, Role of the Eastern California shear zone inaccommodating Pacific-North America plate motion: Geophysical Research Letters, v. 17, p.1,323-1,326.

Flesch, L.M., W.E. Holt, A.J. Haines, and B. Shen-Tu, 2000, Dynamic of the Pacific-NorthAmerican plate boundary zone in the western United States, Science, 287, 834-836.

Friedrich, A.M., Lee, J., Wernicke, B.P., and Sieh, K., 2004, Geologic context of geodetic dataacross the Basin and Range normal fault, Crescent Valley, Nevada: Tectonics, v. 23, p. 1-24.

Gan, W., Svarc, J.L., Savage, J.C., and Prescott, W.H., 2000, Strain accumulation across theEastern California Shear Zone at latitude 36º30´N: Journal of Geophysical Research, v. 105,p. 16,229-16,236.

Gillespie, A.R., 1982, Quaternary glaciation and tectonism in the southeastern Sierra Nevada,Inyo County, California [Ph.D. thesis]: Pasadena, California Institute of Technology, 738 p.

Hammond, W.C., and Thatcher, W., 2004, Contemporary tectonic deformation of the Basin andRange province, western United States: 10 years of observation with the Global PositioningSystem: Journal of Geophysical Research, v. 109, B08403.

Hayman, N.W., Knott, J.R., Cowan, D.S., Nemser, E., and Sarna-Wojcicki, A.M., 2003,Quaternary low-angle slip on detachment faults in Death Valley, California: Geology, v. 31,p. 343.

Huber, N.K., 1981, Amount and Timing of Late Cenozoic Uplift and Tilt of the Sierra Nevada,California-Evidence from the upper San Joaquin Basin: U.S. Geological Society ProfessionalPaper 1197, 28 p.

Jones, C.H., Farmer, G.L., and Unruh, J., 2004, Tectonics of Pliocene removal of lithosphere ofthe Sierra Nevada, California: Geological Society of America Bulletin, v. 116, p. 1408-1422.

Lee, J., Spencer, J., and Owen, L., 2001, Holocene slip rates along the Owens Valley fault,California: Implications for the recent evolution of the Eastern California Shear Zone:Geology, v.29, p. 819-822.

Lindgren, W., 1911, The Tertiary gravels of the Sierra Nevada of California: U.S. GeologicalSurvey Professional Paper 73, 226 p.

Lubetkin, L., and Clark, M., 1988, Late Quaternary activity on the Lone Pine fault, easternCalifornia: Geological Society of America Bulletin, v. 100, p. 755-766.

Machette, M.N., Personius. S.F., Nelson, A.R., Bucknam, R.C., and Hancock, P.L., 1992, TheWasatch fault zone, U.S.A., Annales Tectonicae, v. 6, p. 5-39.

McElhinny, M.W. and Senanayake, W.E., 1982, Variations in the geomagnetic dipole; 1,000 tothe past 50,000 years: Journal of Geomagnetism and Geoelectricity, v. 34, p. 39-51.

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Ohno, M., and Hamano, Y., 1992, Geomagnetic poles over the last 10,000 years: GeophysicalResearch Letters, v. 19, p. 1,715-1,718.

Small, E.E., Anderson, R.S., Repka, J.L., and Finkel, R.C., 1997, Erosion rates of alpine bedrocksummit surfaces deduced from in-situ Be-10 and Al-26: Earth and Planetary Science Letters,v. 150, p. 413-425.

Stock, G.M., Anderson, R.S., and Finkel, R.C., 2004, Pace of landscape evolution in the SierraNevada, California, revealed by cosmogenic dating of cave sediments: Geological Society ofAmerica, v. 32, p. 193-196.

Unruh, J., 1991, The uplift of the Sierra Nevada and implications for late Cenozoic epierogeny inthe western Cordillera: Geological Society of America Bulletin, v. 103, p. 1395-1404.

Unruh, J., Humphery, J., and Barron, A., 2003, Transtensional model for the Sierra Nevadafrontal fault system, eastern California: Geology, v. 31, p. 327-330.

USGS, 2004, United States Geological Survey Quaternary Fault and Fold Database for theUnited States; Nevada, http://earthquakes.usgs.gov/qfaults/nv/index.html.

Wakabayashi, J., and Sawyer, T.L., 2001, Stream incision, tectonics, uplift, and the evolution oftopography of the Sierra Nevada, California: Journal of Geology, v. 109, p. 539-562.

Wesnousky, S.G., Barron, A.D., Briggs, R.W., Caskey, J., Kumar, S., and Owen, L., in press,Paleoseismic transect across the northern Great Basin, USA: Journal of GeophysicalResearch.

Zehfuss, P.H., Bierman, P.R., Gillespie, A.R., Burke, R.A., and Caffee, M.C., 2001, Slip rates onthe Fish Springs fault, Owens Valley, California, deduced from cosmogenic 10Be and 26Aland soil development on fan surfaces: Geological Society of America, v. 113, p. 241-255.

Figure CaptionsFigure 1. Generalized map showing major Quaternary faults along the western boundary of theBasin and Range Province within the Eastern California Shear Zone. Solid circle is located onthe hanging wall of normal faults and arrows indicate relative motion across strike-slip faults.Figure 2. Shaded relief geologic map along the southern Sierra Nevada frontal fault zoneshowing major fault scarps cutting Quaternary alluvial fan surfaces. Location shown in Fig. 1.Figure 3. Detailed geologic map of the Symmes and Shepherd creeks area showing normal faultscarps cutting Quaternary alluvial fan surfaces, cosmogenic radionuclide sample locations, andtopographic profile locations. Boxes show calculated 10Be boulder age for each sample and ageof abandonment for each surface; *indicates boulder sample age not calculated in the weightedmean. Location shown in Fig. 2.Figure 4. Topographic profiles across fault scarps cutting Qf2a, Qf2b, and Qf3a alluvial fansurfaces showing magnitude of vertical offset. Vertical elevation is relative to an arbitrary datum.Location of profiles shown in Fig. 3.

TABLE 1. SUMMARY OF SURFACE AGES, VERTICAL OFFSETS, AND SLIP RATES

Surface Age ± error (ka)* Vertical offset ofMaximummeasured

Vertical sliprate

Horizontal sliprate†

  (ka) dated surface (m)vertical offset (m) (mm/yr) (mm/yr)Qf1 138 ± 35.2 23.3 ± 4.7# 40.8 ± 8.2# 0.2-0.3 ± 0.1% 0.1-0.2 ± 0.1%

Qf2a Qf1 > Qf2a > Qf2a — 41.0 ± 8.2 0.3-0.6 ± 0.1 0.2-0.3 ± 0.1Qf2b 66 ± 16.0 11.9 ± 2.4 21.9 ± 4.4 0.2-0.3 ± 0.1 0.1-0.2 ± 0.1Qf3a 23 ± 5.9 10.2 ± 2.0 10.2 ± 2.0 0.4 ± 0.1 0.3 ± 0.1

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Qf3c 5 ± 1.2 6.9 ± 1.4 — 1.4 ± 0.4 0.8 ± 0.2*Age estimates are calculated using a boulder surface erosion rate of 0.3 mm/yr.†Slip rates are calculated assuming a 60º fault dip.#Because the hanging wall surface is younger than the footwall surface, measured vertical offset is a minimum.%Slip rate estimate is a minimum.

NEVADA

CALIFORNIA

Bishop

OwensLake

LonePine

BigPine

Figure 2

Fish Lake Valley fault zone

Death Valley fault zone

Owen

s Valley fault zon

e

White M

ountains fault zone

Dee

p Sp

rings

faul

t

Hunter Mountain fault

Panamint V

alley fault

Tow

ne P

ass

faul

t

Sierra Nevada

VolcanicTableland

N

6040200

kilometers

NEVADA

CALIFO

RNIA

37°

36°

37°

36°

118° 117°

118° 117°

Fig. 1, Le et al.

Qf2

Qf3

Qf3

Qf3

Qvf

Ow

ens Valley fault

Qf3

Qf2

Qf2

Qf2

Qf2

Qf2

Qf2

Qf2

Qf2

Qf1

Qf3

Oak Creek

I ndependence Cr e

ek

Sy mmes Creek

Shepherd Cree k

Bairs

Creek

L one Pi ne Creek

L

ubkin Creek

Sierra Nevada

Alabam

a Hills

Qf3 surface

Qua

tern

ary

Qf4 present day channels

Stratigraphic contact

Qf1 surfaceQf2 surface

Older bedrock, undifferentiated

Qvf valley fill

Fault scarp (hachures on relative downthrownside)

Explanation

0 5

kilometers

C

D

A

B

Figure 3

118°17'

36°45'

36°35'

Fig. 2, Le et al.

K17K19K18

K16

K15

K14

K12

K13

K9K10

K11

K8K7

K6

K4

K2K3

K5Qf1

Qf2b

Qf2a

Qf2b

Qf2b

Qf2a

Qf2a

Qf2a

Qf2a

Qf2a Qls

Qf3a

Qf3a

Qf3c

Q4

Q4

Q4

Qf3c

Qf3c

Qf3b

Qf3b Qf3b

Qf3b

Qf3b

Qf3b

Qf3a

Qf3a

Shepherd Creek

S

ymm

es C

reek

P1

P2

P3

Qf3c Surface Age

K7 6 ± 1 K8 4 ± 1K9 3 ± 1K10K11

4 ± 15 ± 1

Sample # 10Be age ± error

Mean age 5 ± 1 ka

Qf4 Surface AgeSample # 10Be age ± error

4 ± 1K18 5 ± 1K19 4 ± 1

K17

Mean age 4 ± 1 ka

Qf2b Surface Age

K2* 100 ± 2 K3K4*

59 ± 225 ± 1

K5 73 ± 2K6 70 ± 3

Sample # 10Be age ± error

Mean age 66 ± 16 ka

Qf3a Surface AgeSample # 10Be age ± error

K13 25 ± 1K14 19 ± 1K15 32 ± 1K16 23 ± 1

Mean age 23 ± 6 ka

K12 40 ± 1

118°15'118°16'

36°44'

N

0 1

kilometers

Explanation

Qf4, present day channels

Fault scarp (hachureson relative downthrownside)

Qls, landslide

Qf3c, alluvial fan surface

Qf3b, alluvial fan surface

Qf3a, alluvial fan surface

Qf2b, alluvial fan surface

Qf2a, alluvial fan surface

Qf1, alluvial fan surface

Bedrock,undifferentiated

Stratigraphic contact

Fig. 3, Le et al.

0 50 100 150 200Horizontal distance (m)

0

20

40

Ele

vatio

n (m

)

0 50 100 150 200 250 300 350Horizontal distance (m)

00

100 200 300 400 500 600 700Horizontal distance (m)

0

20

40

60

Ele

vatio

n (m

)

100

200

Ele

vatio

n (m

)

net vertical offset of Qf2b: 11.9 ± 2.4 m

minimum vertical offset of Qf2a: 41.0 ± 12.3 m

net vertical offset of Qf3a: 10.2 ± 3.0 m

2.0 ± 0.6 m3.2 ± 1.0 m

6.7 ± 2.0 m

11.4 ± 4.0 m

10.7 ± 3.0 m

10.3 ± 3.1 m

8.6 ± 2.6 m

Qf2b

Qf2b

Qf2a

Qf3b

Qf3a

Qf3a

Profile 1

Profile 3

Profile 2

vertically exaggerated by 1.5

Fig. 4, Le et al.

Data Repository 1: CRN Geochronology

Samples of approximately 300 to 1000 g were collected from the top 1 to 5 cm of eachboulder using a rock hammer and chisel. Twenty-four quartz-rich granitic boulders were sampledfrom five different alluvial surfaces. Boulders were selected from locations where there was littleor no apparent evidence of boulder exhumation. Sample sites were recorded on aerialphotographs using a Garmin GPS to locate the position of each sample site to within ~10 m.Once collected, samples were crushed, ground, pulverized, and sieved to a grain size of 250 to500 microns.

A leaching procedure was used to purify the quartz and to remove meteoric 10Be (Kohl andNishiizumi, 1992). Beryllium carrier was then added to the sample as it was dissolved in HF andBe was separated by ion exchange chromatography (Kohl and Nishiizumi, 1992). Beryllium wasthen precipitated as the hydroxide and converted to beryllium oxide (Kohl and Nishiizumi, 1992;Gosse and Phillips, 2001) by ignition in quartz at 750°C. The oxide was mixed with niobiumpowder prior to determination of 10Be using the LLNL CAMS FN tandem van de Graaffaccelerator mass spectrometer. Beryllium-10 was determined relative to standards prepared froman ICN 10Be solution by K. Nishiizumi, using a 10Be half-life of 1.5x106 y.

The measured isotope ratios were converted to radionuclide concentrations in quartz usingthe total Be in the samples and the sample weights (Table R1). Age determinations werecalculated with a sea-level, high-latitude production rate of 5.16 at/g-quartz-y using scalingfactors in Lal (1991) as modified by Stone (2000) with a SLHL production by muons accountingfor 3% of the total. A correction for variation in the geomagnetic field was applied to determinethe final age of each sample as described in Nishiizumi et al. (1989) using the SINT800geomagnetic intensity assessment (Valet, private communication). The topographic and depthcorrections were performed by numeric integration of the flux for the dip and topographycorrected elevation at all azimuth directions.

References:Gosse, J.C. and Phillips, F.M., 2001, Terrestrial in situ cosmogenic nuclides: theory and

application: Quaternary Science Reviews, v. 20, p. 1475-1560.Kohl, C.P. and Nishiizumi, K., 1992, Chemical isolation of quartz for measurement of in-situ-

produced cosmogenic nuclides: Geochimica et Cosmochimica Acta, v. 56, p.3583-3587.Lal, D., 1991, Cosmic ray labeling of erosion surfaces: in situ nuclide production rates and

erosion models: Earth and Planetary Science Letters, v. 104, p. 429-439.Nishiizumi, K, Winterer, E. L., Kohl, C. P., Klein, J., Middleton, R., Lal, D., and Arnold, J. R.,

1989, Cosmic ray production rates of 10Be and 26Al in quartz from glacially polished rocks;Journal of Geophysical Research, v. 94, p. 17907-17915.

Stone, J.O., 2000, Air pressure and cosmogenic isotope production: Journal of GeophysicalResearch, v. 105, p. 23,753-23,759.

TA

BL

E R

1: S

UM

MA

RY

OF

10B

e M

OD

EL

AG

ES

WIT

H E

RO

SIO

N E

STIM

AT

ES

FO

R T

HE

SO

UT

HE

RN

SIE

RR

A N

EV

AD

A F

RO

NT

AL

FA

UL

T Z

ON

E

Sam

ple

Alti

tude

Lat

itude

Lon

gitu

deD

epth

&T

hick

ness

Lon

gIn

term

edia

teSh

ort

10B

e m

easu

red

No

Ero

sion

Err

or3.

m/M

yer

osio

nE

rror

nam

e(m

)(N

)(W

)to

pogr

aphy

of s

ampl

edax

is o

fax

is o

fax

is o

f(1

06 at

om g-1

)

10B

e ag

e(k

a)*

±10

Be

age

(ka)

†±

corr

ectio

nla

yer

(cm

)bo

ulde

r (m

)bo

ulde

r (m

)bo

ulde

r(m

)

Fan

Surf

ace,

Qf1

K20

1887

36°4

1.62

911

8°14

.777

0.96

51.

31.

10.

90.

62 ±

0.3

12 9

6.3

2.4

120.

13.

0

K21

1887

36°4

1.62

611

8°14

.778

0.96

51.

40.

80.

71.

78 ±

0.0

4411

8.4

2.9

164.

64.

1

K22

1890

36°4

1.63

011

8°14

.763

0.99

11.

61.

50.

82.

20 ±

0.0

5510

9.4

3.0

145.

14.

0

K23

§18

9336

°41.

607

118°

14.7

920.

965

0.7

0.6

0.5

2.10

± 0

.057

76.

52.

3 9

1.7

2.8

K24

§18

8436

°41.

627

118°

14.7

760.

974

0.8

0.6

0.4

1.43

± 0

.043

66.

52.

2 7

7.5

2.6

Ari

thm

etic

mea

n of

sam

ple

ages

± e

rror

#10

6.3

± 27

138.

2 ±

35

Fan

Surf

ace,

Qf2

b

K2§

1869

36°4

3.84

811

8°16

.482

0.97

23.

52.

52

1.53

± 0

.036

82.5

2.0

99.

62.

4

K3

1871

36°4

3.78

111

8°16

.488

0.96

32.

51.

41.

39.

60 ±

0.0

3151

.71.

7 5

8.6

1.9

K4§

1873

36°4

3.85

111

8°16

.486

0.99

11.

20.

80.

50.

44 ±

0.0

1723

.90.

9 2

4.9

1.0

K5

1859

36°4

3.82

111

8°16

.414

0.96

42

1.5

21.

17 ±

0.0

3863

.72.

1 7

3.4

2.4

K6

1859

36°4

3.82

511

8°16

.408

0.96

41.

50.

50.

41.

12 ±

0.0

4061

.22.

2 7

0.4

2.5

Ari

thm

etic

mea

n of

sam

ple

ages

± e

rror

#57

.7 ±

11

65.9

± 1

6

Fan

Surf

ace,

Qf3

a

K12

1881

36°4

3.24

511

8°16

.104

0.98

23.

41.

61.

17.

05 ±

0.0

0937

.10.

939

.71.

0

K13

1895

36°4

3.19

811

8°16

.091

0.98

21.

61.

30.

44.

51 ±

0.0

0224

.20.

525

.30.

5

K14

1903

36°4

3.15

911

8°16

.096

0.98

21.

31.

11

3.40

± 0

.002

18.2

0.5

18.9

0.5

K15

1901

36°4

3.15

811

8°16

.067

0.99

21.

10.

70.

55.

82 ±

0.0

0330

.60.

932

.41.

0

K16

1900

36°4

3.15

411

8°16

.062

0.98

31.

61.

20.

44.

07 ±

0.0

0921

.90.

522

.80.

5

Ari

thm

etic

mea

n of

sam

ple

ages

± e

rror

#23

.4 ±

623

.4 ±

6

Fan

Surf

ace,

Qf3

c

K7

1852

36°4

3.83

511

8°16

.357

0.98

22

1.4

1.2

1.08

± 0

.003

6.3

0.2

6.3

0.2

K8

1853

36°4

3.77

611

8°16

.285

0.97

35

32

6.98

± 0

.003

4.3

0.2

4.3

0.2

K9

1853

36°4

3.77

611

8°16

.285

0.98

24

3.3

35.

11 ±

0.0

033.

10.

23.

10.

2

K10

1846

36°4

3.82

111

8°16

.275

0.99

12.

11.

31

6.67

± 0

.001

3.8

0.6

3.8

0.6

K11

1847

36°4

3.80

211

8°16

.225

0.97

31.

20.

60.

58.

54 ±

0.0

045.

20.

25.

20.

2

Ari

thm

etic

mea

n of

sam

ple

ages

± e

rror

#4.

6 ±

14.

6 ±

1

Fan

Surf

ace,

Qf4

K17

1726

36°4

3.12

111

8°14

.886

0.98

31.

60.

80.

36.

13 ±

0.0

024.

10.

24.

10.

2

K18

1727

36°4

3.11

911

8°14

.903

0.98

32

1.1

16.

74 ±

0.0

024.

50.

14.

50.

1

K19

1727

36°4

3.11

911

8°14

.903

0.98

22

1.3

0.8

6.21

± 0

.003

4.2

0.2

4.2

0.2

Ari

thm

etic

mea

n of

sam

ple

ages

± e

rror

#4.

3 ±

14.

3 ±

1

Lan

dslid

e

K1

2164

38°4

8.21

611

8°18

.554

0.98

21.

51

0.7

3.81

± 0

.009

16.5

4.0

16.5

4.0

Ari

thm

etic

mea

n of

sam

ple

ages

± e

rror

#

16.5

± 6

16

.5 ±

6

Notes:

10B

e m

odel

age

s fo

r th

e so

uthe

rn S

ierr

a N

evad

a ar

ea.

Err

or r

epor

ted

in th

e er

ror

colu

mn

is a

naly

tical

.

§ Bou

lder

sam

ples

that

are

not

use

d in

the

calc

ulat

ion

of th

ear

ithm

etic

mea

n.

# 10

Be

mod

el e

xpos

ure

ages

rep

orte

d w

ith e

rror

s in

thou

sand

s of

year

s.