The Eastern California shear zone is an active, north-northwest–trending zone of intraplate right-lateral shear that absorbs ~25% of Pacifi c-North America relative plate motion. The Stateline fault system (SFS), which includes several previously recog-nized, discontinuously exposed Quaternary structures along the California-Nevada bor-der, is in this paper defi ned as a continuous, 200-km–long zone of active dextral shear that includes (from south to north) the Mes-quite, Pahrump, and Amargosa Valley seg-ments. Recognition of this system expands the known extent of the Eastern California shear zone ~50 km to the east-northeast from its traditionally recognized boundary along the Death Valley fault system. Proximal volcanic and rock avalanche deposits off-set across the Mesquite segment of the SFS indicate 30 ± 4 km of slip on this structure since 13.1 ± 0.2 Ma. This offset is an order of magnitude larger than previous estimates across this section of the SFS, but it is consis-tent with larger offsets previously proposed for the central and northern sections. The total offset and averaged slip rate since mid-Miocene time (2.3 ± 0.35 mm/yr) are similar to those of other major faults across this por-tion of the Basin and Range, which, from east to west, include the Death Valley, Panamint Valley-Hunter Mountain, and Owens Valley fault systems. However, in contrast to these faults, the average post–mid-Miocene slip rate on the SFS is approximately twice that
estimated from present-day geodetic observa-tions and an order of magnitude greater than estimates of average post–mid-Pleistocene slip rates. This discrepancy between long-term, short-term, and geodetically derived slip rates differs from other geologic-geo-detic, slip-rate discrepancies in the Eastern California shear zone, where geodetic slip rates are signifi cantly faster than both long-term and short-term geologic slip rates. This suggests that either the slip rate on the SFS has diminished over time, such that the sys-tem is an abandoned strand of the relatively young Eastern California shear zone, or that the present-day slip rate represents a tran-sient period of slow slip, such that strands of the shear zone must accommodate a complex spatial and temporal distribution of slip.
Keywords: Eastern California shear zone, state-line fault, tectonics, fault offset, fault slip rate, and slip rate discrepancy
INTRODUCTION
Pacifi c-North America plate motion is accom-modated across a broad zone of faulting on the western margin of the continental United States. The San Andreas fault system absorbs the great-est portion of the 48 mm/yr of relative plate motion (~35 mm/yr; e.g., Minster and Jordan, 1987; Bennett et al., 2003). Most of the remain-der is accommodated by the Eastern California shear zone, a diffuse array of primarily north-west-striking faults to the east and south of Sierra Nevada/Great Valley microplate (Dokka and Tra-vis, 1990). This relatively young (<6-Ma) system of predominantly right-lateral, strike-slip faults currently accommodates ~9 mm/yr of north-northwest motion of the Sierra Nevada/Great Val-ley microplate relative to the eastern Great Basin, which, in turn, accommodates an additional 2–3 mm/yr of displacement of the Sierran block
relative to North America (Bennett et al., 2003). The Eastern California shear zone is superim-posed on the strongly transtensional central Basin and Range province, which began to evolve in the early Miocene as the Pacifi c-North America transform boundary began to grow (Atwater and Stock, 1998; Wernicke, 1992). Quantitative reconstructions of the continental geology show that from 16 to 6 Ma, prior to the opening of the Gulf of California and development of the San Andreas system, ~50% of Pacifi c-North America motion (~20 mm/yr) was accommodated in the Basin and Range (Wernicke et al., 1988; Dick-inson and Wernicke, 1997; Wernicke and Snow, 1998; McQuarrie and Wernicke, 2005). After 6 Ma, Basin and Range average displacement rate and contribution to the total strain budget decreased by a factor of two, as a result of more coastwise relative plate motion (less extensional component) and more effective localization of strain along the San Andreas system (Atwater and Stock, 1998; Oskin and Stock, 2003). The shear zone thus represents an overprint of a rela-tively slow, diffuse, transform system on the older transtensional system, and has been a key locale for studying the spatial and temporal distribution of slip in an active fault system (e.g., Reheis and Dixon, 1996; Lee et al., 2001; Snow and Wer-nicke, 2000; Dixon et al., 2003; Wernicke et al., 2004; Faulds et al., 2005; Wesnousky, 2005).
Recent analyses of geodetic data from contin-uous Global Positioning System (GPS) stations spanning the Eastern California shear zone sug-gest that the eastern limit of dextral Pacifi c-North America shear between latitudes 35° N and 37° N lies to the east of Death Valley along the Cali-fornia-Nevada state line (Fig. 1A; Wernicke et al., 2004; Hill and Blewitt, 2006). These results indicate the potential existence of a dextral fault ~50 km east of the easternmost fault considered in previous tectonic models of this region (e.g., Snow and Wernicke, 2000; Miller et al., 2001; Dixon et al., 2003). A northwest-southeast– trending zone
Stateline fault system: A new component of the Miocene-Quaternary Eastern California shear zone
Bernard Guest†
Nathan Niemi‡
Brian WernickeDivision of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA
†Present address: Department für Geo- und Um-weltwissenschaften, Sektion Geologie, Ludwig-Max-imilians Universität, Luisenstraβe 37, München, D-80333, Germany; [email protected].
‡Present address: Department of Geological Sci-ences, University of Michigan, 1100 North Univer-sity Avenue, Ann Arbor, Michigan 48109, USA.
GSA Bulletin; November/December 2007; v. 119; no. 11/12; p. 1337–1346; doi: 10.1130B26138.1; 5 fi gures; 1 insert; Data Repository Item 2007257.
Guest et al.
1338 Geological Society of America Bulletin, November/December 2007
124°W 123°W 122°W 121°W
120°W
120°W
119°W
119°W
118°W
118°W
117°W 116°W 115°W 114°W
39°N
40°N
41°N
34°N
33°N
123°
W12
1°W
117°
W11
4°W
117°W
116°30'W
116°30'W
116°W
116°W
115°30'W
37°N
35°3
0'N
117°
W
36°N
35°30'N
C
124°W 123°W 122°W 121°W
120°W
120°W
119°W
119°W
118°W
118°W
117°W 116°W 115°W 114°W
39°N
40°N
41°N
34°N
33°N
123°
W12
1°W
117°
W11
4°W
YMYM
BMBMBM
KRKRKR
NRNRRRRR
NRRR
YM
Death Valley
Shoshone
Tecopa
MRMR
NYMNYMIMIMMMMM
MR
NYMIM
CMCM TMTMCM TM
MM
Spring MountainsSpring Mountains
Funeral MountainsFuneral Mountains
Ivanpah Valley
Lanfair Valley
Black MtnsBlack Mtns
~30 km~30 km~30 km
NDVFCFZNDVFCFZ
IFIF
RV
FR
VFYMYM
BMBMBM
KRKRKR
NRNRRRRR
NRRR
YM
Las Vegas
Primm
PahrumpBeatty
MRMR
NYMNYMIMIMMMMM
MR
NYMIM
CMCM TMTMCM TM
MM
Spring MountainsSpring Mountains
Funeral MountainsFuneral Mountains
Black MtnsBlack Mtns
~30 km~30 km~30 km
SFSSFS
Eldorado Valley
Amargosa Valley segmentAmargosa Valley segmentAmargosa Valley segment
Pahrump SegmentPahrump SegmentPahrump Segment
Mesquite SegmentMesquite SegmentMesquite Segment
PF
PMF
LFFIF
SDVFZ
TMF
BLF
BF
LWF
HDF
HLFZWSVFZ
PLFZ
LHFHF
CF
CRF
EFZ
SJFZ
SAF
GF
SFS
SAF
RCF
HF
Age of Offset MarkersPliocene
Mid-Late Miocene
Early Miocene
Early Cenozoic
Mesozoic
Paleozoic
CF
SGF
DVFCFZ
HMF
KCF
OVFS
GHFZBSF
BWFZ
1
1
1
11 2
2
1
12
2
2
2
26
6
2
2
2
3
3
3
4
3
3
3
4
4
45
5
1
1
1
A
B
Stateline fault system: A new component of the Miocene-Quaternary Eastern California shear zone
Geological Society of America Bulletin, November/December 2007 1339
of discontinuously exposed dextral faults has been described, extending some 200 km along the California-Nevada border, from the town of Primm, Nevada, in the south, to as far north as the town of Beatty, Nevada (Figs. 1B and 1C; e.g., Schweickert and Lahren, 1997), consistent with the new geodetic observations. This zone of faulting is defi ned in this paper as the Stateline fault system (SFS), and comprises the previously described Pahrump fault (Piety, 1995; Anderson, 1998), Pahrump fault zone (Liggett and Childs, 1973; Stewart, 1988; Wright, 1989) and Pahrump Valley fault zone (Hoffard, 1991; dePolo, 1998); Stewart Valley fault (Stewart et al., 1968; Burch-fi el et al., 1983; Carr, 1984); Amargosa River fault zone (Donovan, 1991; Anderson et al., 1995; Piety, 1995; dePolo, 1998); and Stateline fault (Hewett, 1956) (SFS; Figs. 1B and 1C).
Because no equivalent active structures are described in the region immediately northeast of the SFS, and because geodetic motions through-out this region are stable at the limit of detection (~0.2 mm/yr level; Bennett et al. 2003), we inter-pret the SFS as the northeasternmost component of the Eastern California shear zone between latitudes 35° N and 37° N. It has received little attention by workers focusing on understanding the long- and short-term strain distribution in the shear zone (Bos, 2005; Dixon et al., 2003; Dixon et al., 1995; Dokka and Macaluso, 2001; Oldow, 2003), in part because, unlike other major dextral faults across this region, most of its trace is developed in poorly consolidated, late Quaternary lacustrine deposits and is therefore obscured by late Holocene erosion. We partition its trace into three primary segments separated by contractional (left) step-overs, which, from south to north, include the Mesquite, Pahrump, and Amargosa segments (Fig. 1C).
Previous estimates of offset across the SFS include ~3 km on the Mesquite segment (Walker et al., 1995); a range of ~10 km (Burchfi el et al., 1983) to 15–19 km (R.L. Christiansen, personal commun. in Stewart et al., 1968) on the Pah-rump segment; and 25–45 km on the Amargosa segment (Poole and Sandberg, 1977; Schweick-ert and Lahren, 1997; Stevens, 1991; Cooper et al., 1982). All of these estimates are based on offsets of pre-Cenozoic markers, such as Paleo-zoic isopachs and facies boundaries or Mesozoic contractional structures (Fig. 1A). Uncertainties in the locations and original geometries of these markers and their pre-Cenozoic age limit their usefulness for making quantitative estimates of Cenozoic slip rate (Schweickert and Lahren, 1997; Snow and Wernicke, 2000). Such esti-mates generally require the identifi cation of offset, late Cenozoic, proximal sedimentary and volcanic deposits from their sources (e.g., Row-land et al., 1990; Topping, 1993; Niemi et al., 2001; Fryxell and Duebendorfer, 2005).
Limited evidence exists for Quaternary off-set along the SFS; however, this may be due to the easily eroded nature of the playa deposits through which the fault is mostly developed and the lack of quantitative age data on Quaternary deposits in the region (e.g., Anderson, 1998). The Amargosa segment of the SFS is believed to have ruptured in the Holocene on the basis of fault scarp morphology (Piety, 1995), while two separate rupture events on the Pahrump segment are presumably Holocene in age (Anderson et al., 1995; Menges et al., 2003). Holocene activ-ity is broadly ascribed to the SFS on the basis of fault-scarp morphology on the eastern side of the Nopah Range (Schmidt and Davidson, 1999), and geophysical studies indicate dis-placement along the full 60-km length of the
Pahrump segment (Shields et al., 1997; Louie et al., 1998). High-resolution, Airborne Laser Swath Mapping (ALSM) of the Pahrump seg-ment of the SFS (Niemi et al., 2005) suggests fault offsets are developed in sediment believed to be late Quaternary in age (dePolo et al., 2003). The Late Quaternary slip rate on the SFS is estimated to be less than 0.2 mm/yr (Ander-son, 1998) but greater than 0.1 mm/yr, the latter fi gure based on geophysical images of an off-set spring mound along the Pahrump segment of the fault (Louie et al., 1998). Seismic haz-ards analyses of the Yucca Mountain Nuclear Waste Repository assign a slip-rate estimate of 0.005–0.07 mm/yr to the Pahrump segment of the SFS and 0.01–0.05 mm/yr to the Amargosa segment (Stepp et al., 2001). These slip rates are presumed to average slip-over Late Pleistocene or early Holocene time, and are based largely on the geomorphic characteristics of the fault zone and the estimated ages of geological depos-its that have been disrupted by faulting (e.g., Anderson, 1998). To date, no post-Miocene geological markers offset by the SFS yield both unambiguous displacement data and reliable, absolute age control.
Present-day rates of deformation are based on analysis of GPS data from the Basin and Range Geodetic Network (BARGEN; Wernicke et al., 2004; Hill and Blewitt, 2006), which spans the Amargosa segment of the SFS well to the east of the Death Valley fault zone. Shear strain rates in this region are greater than can be explained by far-fi eld effects of the Death Valley fault zone, according to dislocation models with nominal fault-slip rates and locking depths (Wernicke et al., 2004; Hill and Blewitt, 2006). The geodetic data and reasonable fault parameters applied to Eastern California shear zone faults suggest
Figure 1. (A) Map showing the position of the SFS relative to the other major fault zones involved in the accommodation of dextral transla-tion along the Pacifi c-North America Plate boundary. Black triangles are continuous GPS sites. Displaced arrows show offsets on major dextral faults in this system, color-coded by the age of the offset marker (see Table DR11 for notes and references regarding fault offsets), numbers distinguish between offset markers on a fault that are the same age (see Table DR11). (B) Map of the detailed trace of the SFS and major nearby structures. The white arrow points to the Devil Peak rhyolite intrusion, and the black arrow points to the offset exposures at Black Butte. (C) Landsat ETM+ mosaic of the same region is shown in Figure 1B. Trace of the SFS is clearly discriminated by vegetation lineaments and soil-color changes as it runs through playa along the California-Nevada border (open arrows indicate surface expression of the fault zone). Note the absence of topographic expression of the fault in 30-m DEM (digital elevation model) data in Figure 1B. White brackets defi ne the three major segments of the SFS, as denoted in Figure 1B. Abbreviations used throughout the fi gure: HF—Hayward fault, RCF—Rogers Creek fault, CF—Calaveras fault, SAF—San Andreas fault, SGF—San Gregorio fault, EF—Elsinore fault, SJFZ—San Jacinto fault zone, PMF—Pinto Mountain fault, HDF— Helendale fault, LHF—Lockheart fault, LWF—Lenwood fault, CRF—Camprock fault, HF—Hidalgo fault, CF—Calico fault, BF—Blackwater fault, PF—Pisgah fault, BLF—Bicycle Lake fault, TMF—Tiefort Mountain fault, FIF—Fort Irwin fault, GF—Garlock fault, SDVFZ—Southern Death Valley fault zone, KCF—Kern Canyon fault, OWFS—Owens Valley fault system, HMF—Hunter Mountain fault, DVFCFZ—Death Valley Furnace Creek fault zone, IF—Ivanpah fault, SFS—Stateline fault system, RVF—Rock Valley fault., BWF—Bettles Well fault, BSF—Benton Spring fault, GHFZ—Gumdrop Hills fault zone, PLFZ—Pyramid Lake fault zone, WSVFZ—Warm Springs Valley fault zone, HLFZ—Honey Lake fault zone, YM—Yucca Mountain, BM—Bare Mountain, CM—Cottonwood Mountains, TM—Tucki Mountain, RR—Resting Spring Range, NR—Nopah Range, KR—Kingston Range, MM—Mesquite Mountains, IM—Ivanpah Mountains, NYM—New York Mountains, MR—McCullough Range.
Guest et al.
1340 Geological Society of America Bulletin, November/December 2007
0.7–1.2 mm/yr of right-lateral shear is accom-modated on structures to the east of the Death Valley fault zone. This shear may be localized on the Amargosa segment, or distributed on sev-eral other known fault strands in the region, but the geodetic data cannot be explained by any models of the shear zone that do not include the SFS or an equivalent suite of structures (Hill and Blewitt, 2006).
We present new evidence showing that 13.1 ± 0.2 Ma proximal volcanic deposits and asso-ciated rock avalanches southwest of the north-ern trace of the Mesquite segment of the SFS at Black Butte are dextrally offset 30 ± 4 km from their source region, northeast of the fault at Devil Peak in the southern Spring Mountains (Fig. 1B). Combined with previous estimates, this result establishes the SFS as a major late Cenozoic structure, comparable in offset and length to the Death Valley, Panamint Valley-Hunter Mountain, and Owens Valley fault sys-tems (Fig. 1A; Table DR11) The time-averaged slip rate on the SFS since 13.1 ± 0.2 Ma of 2.3 ± 0.35 mm/yr is ~20% of the total geodetic, right-lateral displacement rate observed across the western Basin and Range today (e.g., Ben-nett et al., 2003), but is two to three times the ~1 mm/yr geodetic rate measured across the Amargosa segment and environs (Wernicke et al., 2004; Hill and Blewitt, 2006), and twenty times higher than existing estimates based on geologic observations of any portion of the SFS (Anderson, 1998). Thus, the role of the SFS in accommodating contemporary plate boundary deformation is unclear. Furthermore, this result is an important new constraint on the spatial and temporal distribution of strain within the Eastern California shear zone and of the long-term seis-mic hazard predicted for Las Vegas, Pahrump, and the proposed high-level nuclear waste facil-ity at Yucca Mountain.
GEOLOGIC SETTING
Devil Peak
Devil Peak is a small (~2.5-km diameter) hypabyssal rhyolite dome that intruded into Paleozoic carbonate strata of the southern Spring Mountains at 13.1 ± 0.2 Ma (Fig. 1B; Armstrong, 1966; this paper). The intrusion is located east of the present trace of the SFS, and
is composed of fi ne-grained, light-gray, porphy-ritic rhyolite that grades to coarse, crystalline rhyolite in the core of the dome. The intrusion is surrounded by ash and obsidian deposits exposed both east and west of the rhyolite dome. Interbedded with the ash and obsidian (Fig. 2A) are several megabreccia deposits composed of Paleozoic wall rock. The megabreccia deposits are comprised primarily of the Mississippian Monte Cristo and Devonian Sultan formations, with lesser amounts of Ordovician Mountain Spring and Cambrian Nopah and Bonanza King formations (the latter two are mapped together as Goodsprings Dolomite by Hewett, 1956). These units comprise the hanging wall of the Sultan thrust (Plate 1A; Hewett, 1956). West-directed collapse of the hanging wall of the Sul-tan thrust, in response to tilting and uplift due to emplacement of the Devil Peak rhyolites, is the most likely mechanism for the emplacement of the megabreccia, although similar slide sheets to the east of Devil Peak in the Shadow Valley basin have no such apparent direct cause and are presumed to be related to regional detach-ment faulting (Davis and Friedmann, 2005). The megabreccia and volcanic units now unconform-ably overlie Cambrian through Permian strata deformed around the rhyolite dome during the early stages of the rhyolite dome emplacement (Plate 1A; Walker et al., 1981; Massachusetts Institute of Technology (MIT) fi eld camps, 2002, 2003, unpublished map).
Black Butte
Black Butte is a 200-m–high, northwest-trend-ing ridge located at the center of southernmost Pahrump Valley and is composed of ~1000 m of northeast-dipping sedimentary and volcanic strata (Fig. 1B and Plate 1; Hewett, 1956). The southwest fl ank of Black Butte is composed of a series of Cenozoic volcaniclastic and lacus-trine sediments overlain by massive, cliff-form-ing Paleozoic carbonate megabreccia deposits, separated along a sharp contact containing prominent linear scour marks and striations (cf. Figures 4 and 7 of Davis and Friedmann, 2005). The megabreccias are primarily composed of the Mississippian Monte Cristo Formation (Hewett, 1956), with subordinate amounts of the Devo-nian Sultan Formation and Cambrian Nopah and/or Bonanza King formations (Plate 1B), and contain intact blocks >1 km in maximum dimension. Interbedded with the megabreccia are white- and tan-weathering, lacustrine strata that locally contain ash and gypsum. The mega-breccia deposits are resistant and hold up the crest of the butte. The northeast fl ank of the butte is composed of progressively thinner and more discontinuous megabreccia sheets and inter-
bedded lacustrine and pyroclastic deposits that grade upsection into obsidian rock avalanche deposits with a pumiceous matrix (Fig. 2B). The obsidian blocks are up to 1 m in maximum dimension, are angular, unsorted, and ungraded, and show no sign of reworking, indicating depo-sition proximal to source.
Geochemical and Geochronological Analyses
Strong similarities in appearance and com-position of the volcanic units at each locality, and the fact that the megabreccia and rock ava-lanche sheets in both places are derived from the same Paleozoic units, suggest correlation of these two sections and therefore restoration of the deposits at Black Butte to a position within a few kilometers of the rhyolite dome at the time of its emplacement (Fig. 3). To test this hypoth-esis, U/Pb ages on zircons were determined for silicic ash in both sections, and from stony rhyolite of the rhyolite dome. In addition, geo-chemical analyses were performed on obsidian glass blocks from both the Devil Peak and Black Butte sections.
Obsidian block rims were trimmed to remove hydrothermally altered glass, and fragments of the block cores were sent to Activation Labora-tories for trace-element analysis. Trace- element compositions of Black Butte and Devil Peak samples (Tables DR2–DR41) are compared with other well-characterized obsidian sources from the western USA (McDonald et al., 1992; Table DR51). These comparisons reveal strong similarities between the Black Butte and Devil Peak obsidian samples and distinct differences from other localities, especially in concen-trations of Cr, Sr, Sn, Ba, Ce, and Eu (Fig. 4 and Table DR51). Data from the Black Butte and Devil Peak samples were also compared to a more limited suite of trace- element data obtained from Devil Peak obsidian samples as part of an archaeological obsidian source characterization study (Shackley, 1994). Sur-prisingly, trace-element data collected during the archaeological study reveal distinct differ-ences in Sr, Ba, and Ce concentrations between obsidian samples from the west and east sides of Devil Peak (Shackley, 1994; Table DR51). These differences are interpreted to result from variations in wall-rock composition and hydro-thermal activity during intrusion of the Devil Peak rhyolite (Shackley, 1994). Unsurprisingly, the Devil Peak obsidian samples collected from the west side of Devil Peak and charac-terized as part of this study share similar Sr, Ba, and Ce concentrations to previously char-acterized samples from the west side of Devil Peak (Table DR51). However, the Black Butte samples analyzed as part of this study also
1GSA Data Repository Item 2007257, Tables DR1–DR6, Compilation of fault data, Sample location and description information, Trace and major element chemistry of obsidian, Regional comparison of obsid-ian trace element geochemistry, and Ion microprobe U-Pb analytical data of zircons, is available at www.geosociety.org/pubs/ft2007.htm. Requests may also be sent to [email protected].
Stateline fault system: A new component of the Miocene-Quaternary Eastern California shear zone
Geological Society of America Bulletin, November/December 2007 1341
A
D
C
B
E
TPzbr
TafTba
Mm
Mm
TsTs
Tba
TofPzu
Figure 2. Photographs of proximal volcanic facies and slide blocks at Black Butte and Devil Peak. (A) View to the southeast of block and ash fl ow (Tba) overlying air-fall tuff (Taf—volcanic units mapped together as Tr on Plate 1) and megabreccia deposits of Paleozoic carbonates (Tb) along the northeast fl ank of Black Butte. All units are dipping steeply to the northeast. (B) View to the north from the Umpire Perlite Mine (Plate 1A) volcanic units associated with Devil Peak. Block and ash fl ow (Tba) is overlain locally by a thick obsidian (Tof—dark unit on ridge crest in foreground). Undifferentiated Paleozoic carbonates (Pzu) form the skyline ridge in the background. (C) Panoramic view of Black Butte from the southwest toward the northeast showing the sharp contact between smooth slopes underlain by Tertiary lacustrine deposits and overlying cliff-forming Mississippian carbonates. (D) View of sharp basalt contact between Mississippian Monte Cristo For-mation and Tertiary lacustrine deposits, southeast edge of Black Butte. (E) Tilted Mississippian slide block overlying Tertiary lacustrine deposits along southeast edge of Black Butte (photographs D and E by Kevin Mahan).
Guest et al.
1342 Geological Society of America Bulletin, November/December 2007
yield Sr, Ba, and Ce concentrations that indi-cate a source on the west side of Devil Peak. The difference in trace-element concentrations found in obsidian samples from either side of Devil Peak, combined with the striking simi-larity in trace-element concentrations between the Black Butte obsidian sample and obsidian fl ows located on the west side of Devil Peak, strongly suggest a single source for obsidian
breccias now located on the west side of Devil Peak and at Black Butte.
U-Pb geochronological analyses were under-taken on individual zircon grains collected from both Black Butte and Devil Peak (Table DR21). The analyses were performed using a Cameca IMS 1270 ion microprobe at the University of California, Los Angeles, SIMS (Secondary Ion Mass Spectrometer) Facility. Age spectra of the
three samples are statistically indistinguishable from one another (Fig. 5; Table DR61), and are consistent with previous age determina-tions on the Devil Peak rhyolite using the K-Ar method (Armstrong, 1966). The age of the Devil Peak rhyolite, based on the U/Pb data, is 13.1 ± 0.2 Ma, synchronous with the emplacement of silicic eruptive products located at Black Butte and to the west of the intrusion itself.
123
500
1000
1500
3210 654 9 1087
500
-500
-1000
-1500
0
-500
-1000
0
1000
1500
2000Stateline Fault Zone
Black Butte
Sample site Growth strataDevil Peak
Sample site
??
?
?
?
??
? ?
?
?
Devil Peak Rhyolite domeDevil Peak Rhyolite domeDevil Peak Rhyolite dome
Quaternary alluvium
Tertiary alluvium
Tertiary silt
Devil peak ash, volcanic debris
Megabreccia sheet
Glide block of Paleozoic carbonate
Paleozoic carbonate
Detachment fault (inferred position)
Basal landslide glide plane
EW
Trace element data
0.1
1
10
100
1000
Sc Be Cr Co Zn Rb Sr Y Zr Nb Mo Sn Sb Cs Ba La Ce Nd Sm Eu Gd Tb Tm Yb Lu Hf Ta W Pb Th U
Elements
pp
m
Black butteDevil peakBig pineLittle glass-mtnPanum domeClear lake
Figure 3. Schematic cross sections through Black Butte (west of SFS) and Devil Peak intrusion (east of the SFS). Key features are the basal landslide glide plane, which is undeformed and untilted at Devil Peak but is tilted ~65° at Black Butte, and the Spring Mountain break-away detachment fault, above which tilting of the Black Butte is inferred to have occurred.
Figure 4. Trace-element diagram showing a large suite of trace-element compositions for obsidian from Black Butte, Devil Peak, and several other California localities (Tables DR2–DR51). Note that the Black Butte and Devil Peak results are nearly identical, but differ signifi cantly from the trace-element signatures of the other sites, indicating that the Devil Peak obsidian and the Black Butte obsidian are derived from the same magma source and shared similar wall-rock interactions (see text for discussion). Sample locations are shown on Plate 1.
Stateline fault system: A new component of the Miocene-Quaternary Eastern California shear zone
Geological Society of America Bulletin, November/December 2007 1343
DISCUSSION
Correlation of Black Butte and Devil Peak Sections
Based on the similarities of the volcano-stratigraphic succession at Black Butte and Devil Peak, and the proximal nature of the source for each, we propose to restore the sec-tion currently exposed at Black Butte adjacent to the western edge of the Devil Peak intrusion at 13.1 ± 0.2 Ma. The association of a “point deposit,” such as a rock avalanche or mega-breccia deposit, with a “point source,” provides one of the best constraints on tectonic transport in the absence of more discrete piercing lines (Topping, 1993; Fryxell and Duebendorfer, 2005). The total amount of offset of the Black Butte deposits from the Devil Peak source depends on the run-out length and direction of the rock avalanche deposits (e.g., Topping, 1993). Based on exposures of the megabrec-cia at Black Butte, we conservatively estimate the maximum megabreccia sheet to have a volume of ~0.5 km3 (Plate 1B). Using empiri-cal relationships between rock avalanche vol-ume and run-out distance, we estimate that the Black Butte rock avalanche traveled between 3 and 10 km (Scheidegger, 1973; Hsü, 1975; Li, 1983; Ui, 1983; Topping, 1993; Fryxell and Duebendorfer, 2005). The present-day distri-bution of megabreccia deposits at Devil Peak and the topographic bowl that resulted from the emplacement of the Devil Peak rhyolite (Plate 1A) lead us to a preferred interpreta-tion of ~3–4 km of west-southwest–directed run out, followed by 30 km of right-lateral off-set along the SFS. Topography created by the rhyolite intrusion constrains run-out orientation to lie between southwest and northwest. Given this range of permissible run-out orientations, total dextral offset of the deposits along the SFS ranges between 26 and 34 km.
We therefore suggest that 30 ± 4 km of right-lateral slip has been accommodated on the SFS since mid-Miocene time. The minimum, long-term, time-averaged slip rate on the SFS, then, is 2.3 ± 0.35 mm/yr, assuming that the SFS ini-tiated at or before 13.1 ± 0.2 Ma. However, if displacement on the SFS is limited to a shorter time period than the past 13 ± 0.2 Ma, the slip rate on the fault would increase proportionally. For example, if the development of the SFS is related to the opening of the Gulf of California and the concomitant initiation of shear across the Eastern California shear zone, then the 30 ± 4 km of offset may have been accommodated in the past 6–10 Myr (e.g., Snow and Wernicke, 2000; Oskin et al., 2001), yielding slip rates on the SFS of 3–5 mm/yr, respectively.
Slip-Rate Discrepancy
Both contemporary motions derived from GPS geodesy across the Amargosa segment of the SFS of 0.7–1.2 mm/yr (Wernicke et al., 2004; Hill and Blewitt, 2006) and Holocene rates of 0.1–0.2 mm/yr determined from geo-logic observations (Anderson, 1998) are much smaller than the above estimates of long-term slip rate on the SFS. Allowing for the possibil-ity that some of the contemporary motion in this area is related to elastic strain accumulation on the northern Death Valley fault zone and other faults to the west (Dixon et al., 2003), the dis-crepancy is even more striking. This disagree-ment between the short-term geodetic and the long-term geologic slip rates is not entirely unexpected, since such discrepancies have been observed at several localities across normal and
strike-slip fault systems within the Basin and Range and Mojave regions (Peltzer et al., 2001; McClusky et al., 2001; Oskin and Iriondo, 2004; Oskin et al., 2007; Friedrich et al., 2003; Wer-nicke et al., 2000; Friedrich et al., 2004; Niemi et al., 2004). We have identifi ed four possibili-ties that may explain the observed discrepancies in the slip rate. First, it is possible that the pres-ent ~1-mm/yr (or less) geodetic slip-rate and ~0.1-mm/yr geologic slip-rate determinations represent a transient period of slow slip on the SFS, while strain is temporarily transferred to other faults within the Eastern California shear zone. Strain is continuing to accumulate on the SFS, but seismic strain release has been limited through the Holocene. Such a scenario may indicate that seismic strain release on the SFS is clustered on timescales of thousands or tens of thousands of years, while long-term slip rates on
U/Pb ion microprobe ages
0 0
0.4
2
4
6
8
10
12
14
4 6 8 10 18161412 20 22 24 26
Age (Ma)
12 1411 13 15
Nu
mb
er
Rel
ativ
e p
rob
abili
tyBlack Butte ash
Devil Peak rhyolite
Devil Peak ash
Mean age: 13.6 ± 0.5 Ma MSWD: 0.1, n = 4
Mean age: 13.3 ± 0.4 MaMSWD: 0.6, n = 5
Mean age: 12.8 ± 0.2 MaMSWD: 1.0, n = 12
Figure 5. Histogram and relative probability density function of zircon, single-grain, U-Pb ages from Black Butte ash, Devil Peak ash, and Devil Peak stony rhyolite (Tables DR2 and DR61). Age distributions for each sample are statistically indistinguishable from each other, suggesting that these zircons are derived from the same source. Sample locations are shown on Plate 1.
Guest et al.
1344 Geological Society of America Bulletin, November/December 2007
the SFS vary on hundreds of thousands or mil-lion-year timescales (e.g., Friedrich et al., 2003; Niemi et al., 2004).
Alternatively, faults across the Eastern Califor-nia shear zone may have developed sequentially from east to west, such that strain localization along the SFS occurred early in the development of the shear zone, but the high strain rates that the SFS must once have accommodated have now migrated permanently to younger faults to the west as the Eastern California shear zone has evolved. The SFS, then, would be analogous to the San Gabriel or Miller Creek-Palomares faults in California; these faults accommodated rapid slip rates (and signifi cant displacements) early in the development of the San Andreas transform system, but are now thought to be mostly or completely inactive (Powell, 1993; Petersen and Wesnousky, 1994; Wakabayashi, 1999). Evidence of Holocene displacement on the Amargosa and Pahrump segments of the SFS would then be the manifestation of infre-quent seismic events on these faults.
Geologic fault slip rates on the SFS may also be underestimated due to poor exposure of fault scarps developed in unconsolidated Quaternary sediments and a lack of quantitative age con-straints on faulted sediments. Signifi cant dis-crepancies between geodetic and geologic slip rates in the western Mojave Desert (Peltzer et al., 2001; Oskin and Iriondo, 2004) have been reduced but not eliminated by further investiga-tions into long-term geologic slip rates on the faults that comprise the Eastern California shear zone in this region (Oskin et al., 2007). A spring mound imaged by geophysical methods at the southern end of Stewart Valley has been offset ~18 m in a dextral sense (Louie et al., 1998). The age of the spring mound is not directly con-strained, but based on ages of exposed spring mounds in the region, it could be as young as 10 ka (Quade et al., 1995). If so, the Holocene slip rate on the SFS could be as high as 1.8 mm/yr (Louie et al., 1998), in closer agreement with both short- and long-term geologic slip rates.
Finally, the difference between geodetic and geologic slip rates may be related to the lati-tudinal position of the various measurements. The geodetic observations thus far constrain the slip rate on the Amargosa segment, while the geologic observations presented in this paper pertain to the Pahrump and Mesquite segments (Fig. 1B). For example, it is possible that slip on the Mesquite and Pahrump segments of the SFS is transferred westward to the Death Valley-Furnace Creek fault zone via an extension of the observed left (compressional) step-over between the Pahrump and Amargosa segments (Fig. 1B). In such a scenario, the difference in the geodetic and geologic rates would refl ect an
along-strike change in displacement rate on the SFS. Continuous GPS stations recently installed across Amargosa and Pahrump valleys will help to distinguish between these alternatives, while further work to better constrain the Holocene slip rate on all three segments of the SFS is being undertaken.
Irrespective of tighter constraints on the tem-poral and spatial pattern of deformation along the SFS, the magnitude of slip accommodated on this fault since mid-Miocene time indicates that it is integral to understanding the initia-tion and development of the Eastern California shear zone. The observed 30 ± 4 km of slip on the SFS is greater than the amount of Tertiary dextral slip on either the Owens Valley fault (~3–20 km; e.g., Lee et al., 2001; although total slip since Cretaceous time may approach 65 km; Kylander-Clark et al., 2005), or the Panamint Valley-Hunter Mountain fault (8–10 km; Burch-fi el et al., 1987), and is only slightly less than the total Tertiary right-lateral slip on the northern Death Valley-Fish Lake Valley fault (40–50 km; McKee, 1968; Reheis and Sawyer, 1997).
Seismic Hazards
The SFS, as defi ned in this paper, lies within 50 km of metropolitan Las Vegas, cuts directly through the rapidly growing city of Pahrump, Nevada, and passes within 25 km of the proposed nuclear waste repository site at Yucca Mountain. Velocity measurements from space-based geodesy indicate a substan-tially higher slip rate than is indicated by the Quaternary faulting history on the SFS (Wer-nicke et al., 2004; Hill and Blewitt, 2006), and the long-term slip rates and displacement on the SFS since Miocene time presented in this study reinforce the geodetic results. In terms of assessment of seismic hazards for the Pah-rump Valley region, both the slip rate and the total displacement determined through this study are important. The former is of greatest importance to the cities of Pahrump and Las Vegas. Although available evidence suggests that earthquakes greater than Magnitude 7 occur on the SFS (Menges et al., 2003), recur-rence intervals on the SFS have been estimated to be >10 ka (Anderson, 1998; Menges et al., 2003), suggesting a low probability for a large earthquake associated with the fault system. If the long-term slip rate obtained from the off-set of the volcanic succession along the SFS is representative of the average rate of slip on the SFS, then the probability of a large event would increase signifi cantly.
Additional geologic and geodetic work look-ing at the present slip-rate distribution and Qua-ternary slip history of the SFS is ongoing and
will address the question of spatial and temporal slip-rate variations for this fault system.
CONCLUSIONS
Successions of volcanic and sedimentary rock currently separated across the Stateline fault zone are correlated on the basis of strati-graphic similarity, geochemical fi ngerprint, and geochronologic age. This correlation estab-lishes displacement along the Stateline fault of 30 ± 4 km since mid-Miocene (13.1 ± 0.2 Ma) time, although we note that additional, pre–13-Ma displacement could have occurred. The long-term slip rate of 2.3 ± 0.35 mm/yr on the Stateline fault implied by this correlation requires reconsideration of neotectonic activity on this fault, and may suggest reassessment of the hazard potential this fault poses for towns in southwestern Nevada and for the nuclear waste repository at Yucca Mountain. The total slip on the SFS determined by this study implies that the SFS is an integral structure in the develop-ment of the Eastern California shear zone and increases to four the number of major dextral faults that should be considered in tectonic mod-els of the shear zone between latitudes 35° N and 37° N. The discrepancy between geodetic and long-term geologic slip rates on the SFS is opposite that observed across other portions of the Eastern California shear zone and under-scores the importance of deriving fault-slip rates on multiple temporal scales as key to under-standing the evolution of a complex intraconti-nental transform zone.
ACKNOWLEDGMENTS
This research was supported by Department of Energy contract FC-08-98NV12081 and National Science Foundation grant EAR-0453975 to BW and a Texaco Postdoctoral Fellowship at the California Insti-tute of Technology awarded to BG. Some observations in the Devil Peak area were funded by the Lyons Fund at the Massachusetts Institute of Technology through a postdoctoral fellowship to NN. We are especially grateful to D. Burton Slemmons for introducing us in the fi eld to a number of Late Quaternary features along the SFS that he and his students have identi-fi ed and mapped over the years; these features were indispensable to our research. Mike Oskin provided a preprint and critique that substantially improved the presentation of fault offsets in the Mojave Desert. Jeff Lee, Terry Pavlis, and Associate Editor John Wak-abayashi are thanked for their insightful reviews of the original manuscript.
REFERENCES CITED
Anderson, R.E., compiler, 1998, Fault number 1076, Pah-rump fault, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, http://earthquakes.usgs.gov/regional/qfaults.
Anderson, R.E., Crone, A.J., Machette, M.N., Bradley, L.-A., and Diehl, S.F., 1995, Characterization of Quater-nary and suspected Quaternary faults, Amargosa area,
Stateline fault system: A new component of the Miocene-Quaternary Eastern California shear zone
Geological Society of America Bulletin, November/December 2007 1345
Nevada and California: U.S. Geological Survey Open-File Report 95-613, 44 p., 4 sheets.
Armstrong, R.L., 1966, K-Ar dating using neutron activa-tion for Ar analysis: Granitic plutons of the eastern Great Basin, Nevada and Utah: Geochimica et Cosmo-chimica Acta, v. 30, p. 565–600, doi: 10.1016/0016-7037(66)90012-3.
Atwater, T., and Stock, J., 1998, Pacifi c-North America plate tectonics of the Neogene southwestern United States: An update: International Geological Review, v. 40, p. 375–402.
Bennett, R.A., Wernicke, B.P., Niemi, N.A., Friedrich, A.M., and Davis, J.L., 2003, Contemporary strain rates in the northern Basin and Range province from GPS data: Tec-tonics, v. 22, p. 1008, doi: 10.1029/2001TC001355.
Bos, A.G., 2005, Kinematics of the southwestern US defor-mation zone inferred from GPS motion data: Journal of Geophysical Research, v. 110, p. B08405, doi: 10.1029/2003JB002742.
Burchfi el, B.C., Hamill, G.S., and Wilhelms, D.E., 1983, Structural geology of the Montgomery Mountains and the northern half of the Nopah and Resting Spring ranges, Nevada and California: Geological Society of America Bulletin, v. 94, p. 1359–1376, doi: 10.1130/0016-7606(1983)94<1359:SGOTMM>2.0.CO;2.
Burchfi el, B.C., Hodges, K.V., and Royden, L.H., 1987, Geol-ogy of Panamint Valley-Saline Valley pull-apart system, California—Palinspastic evidence for low-angle geom-etry of a Neogene range-bounding fault: Journal of Geo-physical Research, v. 92, p. 10,422–10,426.
Carr, W.J., 1984, Regional structural setting of Yucca Moun-tain, southwestern Nevada, and late Cenozoic rates of tectonic activity in parts of the southwestern Great Basin, Nevada and California: U.S. Geological Survey Open-File Report 84-854, 114 p.
Cooper, J.D., Miller, R.H., and Sundberg, F.A., 1982, Envi-ronmental stratigraphy of the lower part of the Nopah Formation (Upper Cambrian), southwestern Great Basin, in Cooper, J.D., Troxel, B.W., and Wright, L.A., eds., Geology of selected areas in the San Bernardino Mountains, western Mojave Desert, and southern Great Basin, California (Guidebook): Anaheim, Geological Society of America, p. 97–116.
Davis, G.A., and Friedmann, S.J., 2005, Large-scale gravity sliding in the Miocene Shadow Valley Supradetach-ment Basin, Eastern Mojave Desert, California: Earth-Science Reviews, v. 73, p. 149–176, doi: 10.1016/j.earscirev.2005.04.008.
dePolo, C.M., 1998, A reconnaissance technique for estimat-ing the slip rate of normal-slip faults in the Great Basin, and application to faults in Nevada, U.S.A. [Ph.D. the-sis]: Reno, University of Nevada, 199 p.
dePolo, C.M., Ramelli, A.R., and Bell, J.W., 2003, Prelimi-nary geologic map of the Sixmile Spring quadrangle, Nye county, Nevada, and Inyo County, California: Nevada Bureau of Mines and Geology Open-File Report 03-11.
Dickinson, W.R., and Wernicke, B.P., 1997, Reconcili-ation of San Andreas slip discrepancy by a combi-nation of interior Basin and Range extension and transrotation near the coast: Geology, v. 25, no. 7, p. 663–665, doi: 10.1130/0091-7613(1997)025<0663:ROSASD>2.3.CO;2.
Dixon, T.H., Robaudo, S., Lee, J., and Reheis, M.C., 1995, Constraints on present-day Basin and Range deforma-tion from space geodesy: Tectonics, v. 14, p. 755–772, doi: 10.1029/95TC00931.
Dixon, T.H., Norabuena, E., and Hotaling, L., 2003, Paleo-seismology and global positioning system: Earthquake-cycle effects and geodetic versus geologic fault slip rates in the Eastern California shear zone: Geology, v. 31, p. 55–58, doi: 10.1130/0091-7613(2003)031<0055:PAGPSE>2.0.CO;2.
Dokka, R.K., and Macaluso, K.Y., 2001, Topographic effects of the Eastern California Shear Zone in the Mojave Desert: Journal of Geophysical Research, v. 106, p. 30,625–30,644, doi: 10.1029/2000JB000017.
Dokka, R.K., and Travis, C.J., 1990, Role of the eastern California shear zone in accommodating Pacifi c-North American plate motion: Geophysical Research Letters, v. 17, p. 1323–1326.
Donovan, D.E., 1991, Neotectonics of the southern Amar-gosa Desert, Nye County, Nevada, and Inyo County,
California [M.S. thesis]: Reno, University of Nevada, 151 p., 1 plate.
Faulds, J.E., Henry, C.D., and Hinz, N.H., 2005, Kinematics of the northern Walker Lane: An incipient transform fault along the Pacifi c-North American plate boundary: Geology, v. 33, p. 505–508, doi: 10.1130/G21274.1.
Friedrich, A.M., Wernicke, B.P., Niemi, N.A., Bennett, R.A., and Davis, J.L., 2003, Comparison of geodetic and geologic data from the Wasatch region, Utah, and implications for the spectral character of Earth deformation at periods of 10 to 10 million years: Jour-nal of Geophysical Research, v. 108, p. 2199, doi: 10.1029/2001JB000682.
Friedrich, A.M., Lee, J., Wernicke, B.P., and Sieh, K., 2004, Geologic context of geodetic data across a Basin and Range normal fault, Crescent Valley, Nevada: Tecton-ics, v. 23, p. TC2015, doi: 10.1029/2003TC001528.
Fryxell, J.E., and Duebendorfer, E.M., 2005, Origin and trajectory of the Frenchman Mountain block, an exten-sional allochthon in the Basin and Range Province, southern Nevada: The Journal of Geology, v. 113, p. 355–371, doi: 10.1086/428810.
Hewett, D.F., 1956, Geology and mineral resources of the Ivanpah Quadrangle, California and Nevada: U.S. Geological Survey Professional Paper 275, 172 p.
Hill, E.M., and Blewitt, G., 2006, Testing for fault activ-ity at Yucca Mountain, Nevada, using independent GPS results from the BARGEN network: Geo-physical Research Letters, v. 33, p. L14302, doi: 10.1029/2006GL026140.
Hoffard, J.L., 1991, Quaternary tectonics and basin history of Pahrump and Stewart Valley, Nevada and California [M.S. thesis]: Reno, University of Nevada, 138 p., 5 plates.
House, P.K., Ramelli, A.R., and Buck, B.J., 2006, Surfi cial geologic map of the Ivanpah Valley area, Clark County, Nevada: Nevada Bureau of Mines and Geology Map 156, scale 1:50,000.
Hsü, K.J., 1975, Catastrophic debris streams (sturtzstroms) generated by rockfalls: Geological Society of Amer-ica Bulletin, v. 86, p. 129–140, doi: 10.1130/0016-7606(1975)86<129:CDSSGB>2.0.CO;2.
Kylander-Clark, A.R.C., Coleman, D.S., Glazner, A.F., and Bartley, J.M., 2005, Evidence for 65 km of dextral slip across Owens Valley, California, since 83 Ma: Geolog-ical Society of America Bulletin, v. 117, p. 962–968, doi: 10.1130/B25624.1.
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, doi: 10.1130/0091-7613(2001)029<0819:HSRATO>2.0.CO;2.
Li, T., 1983, A mathematical model for predicting the extent of a major rockfall: Zeitschrift für Geomorphologie, v. 24, p. 473–482.
Liggett, M.A., and Childs, J.F., 1973, Evidence of a major fault zone along the California-Nevada state line, 35°30′ to 36°30′N latitude: Argus Exploration Com-pany, National Aeronautics and Space Administration Report of Investigation CR-133140, E73–10733, 13 p.
Louie, J., Shields, G., Ichinose, G., Hasting, M., Plank, G., and Bowman, S., 1998, Shallow geophysical con-straints on displacement and segmentation of the Pah-rump Valley fault zone, California-Nevada border, in Lund, W.R., ed., Proceedings of the Basin and Range Province Seismic Hazards Summit, May 13–15, 1997: Cedar City, Utah, Utah Geological Survey.
Massachusetts Institute of Technology Geophysics Field Course, 1985, A geophysical study of Mesquite Val-ley; Nevada-California border: Journal of Geophysical Research, v. 90, p. 8685–8689.
McClusky, S.C., Bjornstad, S.C., Hager, B.H., King, R.W., Meade, B.J., Miller, M.M., and Monastero, F.C., 2001, Present day kinematics of the Eastern Califor-nia shear zone from a geodetically constrained block model: Geophysical Research Letters, v. 28, doi: 10.1029/2001GL013091.
McDonald, R., Smith, R.L., and Thomas, J.E., 1992, Chem-istry of the subalkalic silicic obsidians: U.S. Geologi-cal Survey Professional Paper 1523, 214 p.
McKee, E., 1968, Age and rate of movement of the north-ern part of the Death Valley-Furnace Creek fault zone, California: Geological Society of America Bulletin,
v. 79, p. 509–512, doi: 10.1130/0016-7606(1968)79[509:AAROMO]2.0.CO;2.
McQuarrie, N., and Wernicke, B.P., 2005, An animated tec-tonic reconstruction of southwestern North America since 36 Ma: Geosphere, v. 1, no. 3, p. 147–172, doi: 10.1130/GES00016.1.
Menges, C.M., Fridrich, C., Blakely, R.J., and Thompson, R.A., 2003, Late Quaternary surface rupture and asso-ciated transpressive uplift on a section of the State Line Fault in south-central Amargosa Desert Basin, south-western Nevada: Eos (Transactions, American Geo-physical Union), v. 84, no. S11D-0327.
Miller, M.M., Johnson, D.J., Dixon, T.H., and Dokka, R.K., 2001, Refi ned kinematics of the Eastern California shear zone from GPS observations, 1993–1998: Jour-nal of Geophysical Research, v. 106, p. 2245–2264, doi: 10.1029/2000JB900328.
Minster, J.B., and Jordan, T.H., 1987, Vector constraints on Western US deformation from space geodesy, neo-tectonics, and plate motions: Journal of Geophysical Research, v. 92, p. 4798–4804.
Niemi, N., Guest, B., and Wernicke, B., 2005, Geomorphic expression and neotectonic evaluation of a diffuse fault system from Airborne Laser Swath Mapping, Pahrump Valley, California and Nevada: Eos (Transactions, American Geophysical Union), v. 86, no. H34B-02.
Niemi, N.A., Wernicke, B.P., Brady, R.J., Saleeby, J.B., and Dunne, G.C., 2001, Distribution and provenance of the middle Miocene Eagle Mountain Formation, and implication for regional kinematic analysis of the Basin and Range province: Geological Society of America Bulletin, v. 113, p. 419–442, doi: 10.1130/0016-7606(2001)113<0419:DAPOTM>2.0.CO;2.
Niemi, N.A., Wernicke, B.P., Friedrich, A.M., Simons, M., Bennett, R.A., and Davis, J.L., 2004, BARGEN con-tinuous GPS data across the eastern Basin and Range province, and implications for fault system dynamics: Geophysical Journal International, v. 159, p. 842–862, doi: 10.1111/j.1365-246X.2004.02454.x.
Oldow, J.S., 2003, Active transtensional boundary zone between the western Great Basin and Sierra Nevada block, western U.S. cordillera: Geology, v. 31, p. 1033–1036, doi: 10.1130/G19838.1.
Oskin, M., and Iriondo, A., 2004, Large-magnitude transient strain accumulation on the Blackwater fault, Eastern California shear zone: Geology, v. 32, p. 313–316, doi: 10.1130/G20223.1.
Oskin, M., and Stock, J., 2003, Marine incursion synchronous with plate-boundary localization in the Gulf of Califor-nia: Geology, v. 31, no. 1, p. 23–26, doi: 10.1130/0091-7613(2003)031<0023:MISWPB>2.0.CO;2.
Oskin, M., Stock, J., and Martín-Barajás, A., 2001, Rapid localization of Pacifi c-North America plate motion in the Gulf of California: Geology, v. 29, p. 459–462, doi: 10.1130/0091-7613(2001)029<0459:RLOPNA>2.0.CO;2.
Oskin, M., Perg, L., Blumentritt, D., Mukhopadhyay, S., and Iriondo, A., 2007, Slip rate of the Calico fault: Implica-tions for geologic versus geodetic rate discrepancy in the Eastern California shear zone: Journal of Geophys-ical Research, v. 112, doi: 10.1029/2006JB004451.
Peltzer, G., Crampé, F., Hensley, S., and Rosen, P., 2001, Transient strain accumulation and fault interaction in the Eastern California shear zone: Geology, v. 29, p. 975–978, doi: 10.1130/0091-7613(2001)029<0975:TSAAFI>2.0.CO;2.
Petersen, M.D., and Wesnousky, S.G., 1994, Fault slip rates and earthquake histories for active faults in southern California: Bulletin of the Seismological Society of America, v. 84, p. 1608–1649.
Piety, L.A., 1995, Compilation of known and suspected Quaternary faults within 100 km of Yucca Mountain, Nevada and California: U.S. Geological Survey Open-File Report 94-112, 404 p., 2 plates.
Poole, F.G., and Sandberg, C.A., 1977, Mississippian paleo-geography and tectonics of the western United States, in Stewart, J.H., Stevens, C.H., and Fritsche, A.E., eds., Paleozoic paleogeography of the western United States: Pacifi c Section, Society of Economic Paleon-tologists and Mineralogists, Pacifi c Coast Paleogeog-raphy Symposium 1, p. 67–85.
1346 Geological Society of America Bulletin, November/December 2007
Geologic and kinematic constraints on evolution of the San Andreas fault system, in Powell, R.E., Weldon, R.J., II, and, Matti, J.C. eds., The San Andreas Fault System: Displacement, palinspastic reconstruction and geologic evolution: Geological Society of America Memoir 178, p. 1–106.
Quade, J., Miffl in, M.D., Pratt, W.L., McCoy, W., and Burckle, L., 1995, Fossil spring deposits in the south-ern Great Basin and their implications for changes in water-table levels near Yucca Mountain, Nevada, dur-ing Quaternary time: Geological Society of America Bulletin, v. 107, p. 213–230, doi: 10.1130/0016-7606(1995)107<0213:FSDITS>2.3.CO;2.
Reheis, M.C., and Dixon, T.H., 1996, Kinematics of the eastern California shear zone: Evidence for slip transfer from Owens and Saline Valley fault zones to Fish Lake Valley fault zone: Geology, v. 24, p. 339–342, doi: 10.1130/0091-7613(1996)024<0339:KOTECS>2.3.CO;2.
Reheis, M.C., and Sawyer, T.L., 1997, Late Cenozoic his-tory and slip rates of the Fish Lake Valley, Emigrant Peak, and Deep Springs fault zones, Nevada and Cali-fornia: Geological Society of America Bulletin, v. 109, p. 280–299, doi: 10.1130/0016-7606(1997)109<0280:LCHASR>2.3.CO;2.
Rowland, S.M., Parolini, J.R., Eschner, E., McAllister, A.J., and Rice, J.A., 1990, Sedimentologic and stratigraphic constraints on the Neogene translation and rotation of the Frenchman Mountain structural block, Clark County, Nevada. in Wernicke, B., ed., Extensional tectonics at the latitude of Las Vegas, Nevada: Boulder, Colorado, Geological Society of America Memoir 176: p. 99–122.
Scheidegger, A.E., 1973, On the prediction of the reach and velocity of catastrophic landslides: Rock Mechanics and Rock Engineering, v. 5, p. 231–236, doi: 10.1007/BF01301796.
Schmidt, K.M., and Davidson, J.G., 1999, Using geomorphic features to constrain tectonic activity near Pahrump Valley, Nevada and California, in Slate, J.L, ed., Pro-ceedings of conference on status of geologic research and mapping, Death Valley National Park: U.S. Geo-logical Survey Open-File Report 99-153, p. 154–55.
Schmidt, K.M., and McMackin, M., 2006, Preliminary sur-fi cial geologic map of the Mesquite Lake 30´ X 60´ quadrangle, California and Nevada: U.S. Geological Survey Open-File Report 2006-1035, 89 p.
Schweickert, R.A., and Lahren, M.M., 1997, Strike-slip fault system in Amargosa Valley and Yucca Moun-tain, Nevada: Tectonophysics, v. 272, p. 25–41, doi: 10.1016/S0040-1951(96)00274-0.
Shackley, M.S., 1994, Intersource and intrasource geochem-ical variability in two newly discovered archaeological
obsidian sources in the southern Great Basin: Bristol Mountains, California and Devil Peak, Nevada: Jour-nal of California and Great Basin Anthropology, v. 16, p. 118–129.
Shields, G., Allander, K., Brigham, R., Crosbie, R., Trimble, L., Sleeman, M., Tucker, R., Zhan, H., and Louie, J.N., 1997, Shallow geophysical survey across the Pahrump Valley fault zone, California-Nevada bor-der: Bulletin of the Seismological Society of America, v. 88, p. 270–275.
Snow, J.K., and Wernicke, B., 2000, Cenozoic tectonism in the central Basin and Range; magnitude, rate, and distribution of upper crustal strain: American Jour-nal of Science, v. 300, p. 659–719, doi: 10.2475/ajs.300.9.659.
Stepp, J.C., Wong, I., Whitney, J., Quittmeyer, R., Abra-hamson, N., Toro, G., Youngs, R., Coppersmith, K., Savy, J., Sullivan, T. and Yucca Mountain PSHA Project Members, 2001, Probabilistic seismic hazard analyses for ground motions and fault displacement at Yucca Mountain, Nevada: Earthquake Spectra, v. 17, p. 113–151, doi: 10.1193/1.1586169.
Stevens, C.H., 1991, Paleogeographic and structural sig-nifi cance of an upper Mississippian facies bound-ary in southern Nevada and east-central California: Geological Society of America Bulletin, v. 103, p. 876–885, doi: 10.1130/00167606(1991)103<0876:PASSOA>2.3.CO;2.
Stewart, J.H., 1988, Tectonics of the Walker Lane belt, west-ern Great Basin—Mesozoic and Cenozoic deformation in a zone of shear, in Ernst, W.G., ed., Metamorphism and crustal evolution of the western United States, Ruby Volume VII: Englewood Cliffs, New Jersey, Prentice Hall, p. 683–713.
Stewart, J.H., Albers, J.P., and Poole, F.G., 1968, Summary of regional evidence for right-lateral displacement in the western Great Basin: Geological Society of Amer-ica Bulletin, v. 79, p. 1407–1413, doi: 10.1130/0016-7606(1968)79[1407:SOREFR]2.0.CO;2.
Topping, D.J., 1993, Paleogeographic reconstruction of the Death Valley extended region: Evidence from Miocene large rock-avalanche deposits in the Amargosa Chaos Basin, California: Geological Society of America Bulletin, v. 105, p. 1190–1213, doi: 10.1130/0016-7606(1993)105<1190:PROTDV>2.3.CO;2.
Ui, Y., 1983, Volcanic dry avalanche deposits: Identifi ca-tion and comparison with nonvolcanic debris stream deposits, in Aramaki, S., and Kushiro, I., eds., Arc volcanism: Journal of Volcanolology and Geothermal Research, v. 18, p. 135–150.
Wakabayashi, J., 1999, Distribution of displacement on, and evolution of, a young transform fault system: The
northern San Andreas fault system, California: Tecton-ics, v. 18, p. 1245–1274, doi: 10.1029/1999TC900049.
Walker, J.D., Beaufait, M.S., and Zelt, F.B., 1981, Geology of the Devil Peak area, Spring Mountains, Nevada: Geological Society of America Abstracts with Pro-grams, v. 13, no. 2, p. 112.
Walker, J.D., Burchfi el, B.C., and Davis, G.A., 1995, New age controls on initiation and timing of foreland belt thrusting in the Clark Mountains, southern Califor-nia: Geological Society of America Bulletin, v. 107, p. 742–750, doi: 10.1130/0016-7606(1995)107<0742:NACOIA>2.3.CO;2.
Wernicke, B., and Snow, J.K., 1998, Cenozoic tectonism in the central Basin and Range: Motion of the Sierran-Great Valley block: International Geology Review, v. 40, p. 403–410.
Wernicke, B.P., 1992, Cenozoic extensional tectonics of the U.S. Cordillera, in Burchfi eld, B.C., Lipman, P.W., and Zorback, M.L., eds., Geology of North America, Vol-ume G-3, The Cordilleran Orogen: Conterminous U.S.: Boulder, Colorado, Geological Society of America, p. 553–581.
Wernicke, B.P., Axen, G.J., and Snow, J.K., 1988, Basin and Range extensional tectonics at the latitude of Las Vegas, Nevada: Geological Society of America Bulle-tin, v. 100, no. 11, p. 1738–1757, doi: 10.1130/0016-7606(1988)100<1738:BARETA>2.3.CO;2.
Wernicke, B., Friedrich, A.M., Niemi, N.A., Bennett, R.A., and Davis, J.L., 2000, Dynamics of plate boundary fault systems from Basin and Range Geodetic Network (BARGEN) and geological data: GSA Today, v. 10, p. 1–7.
Wernicke, B., Davis, J.L., Bennett, R.A., Normandeau, J.E., Friedrich, A.M., and Niemi, N.A., 2004, Tectonic impli-cations of a dense continuous GPS velocity fi eld at Yucca Mountain, Nevada: Journal of Geophysical Research, v. 109, p. B12404, doi: 10.1029/2003JB002832.
Wesnousky, S.G., 2005, Active faulting in the Walker Lane: Tectonics, v. 24, no. TC3009.
Wright, L.A., 1989, Overview of the role of strike-slip and normal faulting in the Neogene history of the region northeast of Death Valley, California-Nevada, in Ellis, M.A., ed., Late Cenozoic evolution of the southern Great Basin: Nevada Bureau of Mines and Geology Open-File Report 89-1, p. 1–11.
MANUSCRIPT RECEIVED 6 NOVEMBER 2006REVISED MANUSCRIPT RECEIVED 25 APRIL 2007MANUSCRIPT ACCEPTED 24 MAY 2007
Printed in the USA
116°W 115°30'W35°3
0'N
36°N
36°3
0'N
NVCA
A
B
115°45'W 115°44'W 115°43'W 115°42'W
35°5
3'N
35°5
4'N
115°29'W 115°28'W 115°27'W 115°26'W
35°41'W35°42'W
35°43'W
Plate 1. (A) Geologic map of Devil Peak, compiled from Hewett (1956), Schmidt and McMackin (2006), House et al. (2006), MIT Field Camp 2002, MIT Field Camp 2003, and N. Niemi (2002, 2003, unpublished map). Black circles on Figures 3A and 3B represent geochronological sample localities. (B) Geologic map of Black Butte (B. Guest, 2005, unpublished map).
A
B
Stateline fault system: A new component of the Miocene-Quaternary Eastern California shear zoneGuest et al.
Plate 1 (A) and (B)Supplement to: Geological Society of America Bulletin, v.119, no. 11/12, doi: 10.1130/B26138.S1
