Paleoseismic Patterns of Quaternary Tectonic and Magmatic Surface Deformation in the Eastern Basin and Range, USA

Home , Black Rock Desert, Cricket Mountains, Sevier Desert, Tule Valley

Research Paper

GEOSPHERE Paleoseismic patterns of Quaternary tectonic and magmatic surface deformation in the eastern Basin and Range, USA

1 2 3 3 3 GEOSPHERE, v. 16, no. 1 T.A. Stahl , N.A. Niemi , M.P. Bunds , J. Andreini , and J.D. Wells 1School of Earth and Environment, University of Canterbury, Christchurch 8140, New Zealand 2Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA https://doi.org/10.1130/GES02156.1 3Department of Earth Science, Utah Valley University, Orem, Utah 84058, USA

12 figures; 3 tables; 1 supplemental file

CORRESPONDENCE: [email protected]; volcanic centers, have events temporally clustered for instance, a segment dominated by crustal or [email protected] ABSTRACT around the timing of Pleistocene volcanism in at lithospheric extension on normal faults can become CITATION: Stahl, T.A., Niemi, N.A., Bunds, M.P., The competing contributions of tectonic and least one instance, and have accommodated exten- dominated by magma-assisted rifting as melt pro- Andreini, J., and Wells, J.D., 2020, Paleoseismic pat‑ magmatic processes in accommodating continen- sion ~2×–10× above geodetic and long-term geologic duction and availability evolve (e.g., Bursik and Sieh, terns of Quaternary tectonic and magmatic surface tal extension are commonly obscured by a lack of rates. We propose a model whereby Pliocene to 1989; Parsons and Thompson, 1991; Ebinger and deformation in the eastern Basin and Range, USA: Geosphere, v. 16, no. 1, p. 435–455, https://doi.org on-fault paleoseismic information. This is especially recent extension in the Sevier Desert is spatially Casey, 2001; Muirhead et al., 2015, 2016). Similarly, /10.1130/GES02156.1. true of the Sevier Desert, located at the eastern mar- partitioned into an eastern magma-assisted rift- spatial variations in magma supply and lithospheric gin of the Basin and Range in central Utah (USA), ing domain, characterized by transient episodes structure can lead to along-strike segmentation of Science Editor: Andrea Hampel where surface-rupturing faults are spatially asso- of higher extension rates during volcanism, and a rifts, with adjacent segments dominated by either Associate Editor: Graham D.M. Andrews ciated with both regional detachment faults and western tectonic-dominated domain, characterized tectonic or magma-assisted extension (e.g., Hay- Quaternary volcanism. Here, we use high-resolution by slower-paced faulting in the Cricket Mountains ward and Ebinger, 1996). Extension can also be Received 21 May 2019 Revision received 28 September 2019 topographic surveys (terrestrial lidar scans and and House Range and more typical of the “Basin and partitioned between these processes within a sin- Accepted 25 November 2019 real-time kinematic GPS), terrestrial cosmogenic Range style” that continues westward into Nevada. gle basin (e.g., Bilham et al., 1999; Ebinger and nuclide (10Be and 3He) exposure dating, 40Ar/39Ar The Sevier Desert, with near-complete exposure and Casey, 2001; Ebinger, 2005; Keir et al., 2006; Ath- Published online 19 December 2019 geochronology, and new neotectonic mapping to the opportunity to utilize a range of geophysical ens et al., 2016; Muirhead et al., 2016), with border distinguish between modes of faulting and exten- instrumentation, provides a globally significant lab- faults typically accommodating tectonic extension sion in a transect across the Sevier Desert. In the oratory for understanding the different modes of and intrabasin faults accommodating both tectonic western Sevier Desert, the House Range and Cricket faulting in regions of continental extension. faulting and extension above shallow intrusions Mountains faults each have evidence of a single (Rowland et al., 2007; Ibs-von Seht et al., 2001; Cal- surface-rupturing earthquake in the last 20–30 k.y. ais et al., 2008; Athens et al., 2016). In all cases, the and have time-integrated slip and extension rates ■■ INTRODUCTION characteristics of active faults at the surface provide of <0.1 and ~0.05 mm yr−1, respectively, since ca. clues that assist in evaluating modes of extension. 15–30 ka. These rates are similar to near-negligible Continental extensional provinces, or rifts, are In magma-assisted rifting, extension in the modern geodetic extension estimates. Despite rel- commonly partitioned into segments in which defor- upper crust is partly accommodated by dike injec- atively low geologic, paleoseismic, and modern mation is dominated by either magma-assisted or tion and secondary faulting around the intrusion extension rates, both faults show evidence of con- tectonic extension (e.g., Buck, 1991; Hayward and (e.g., Rubin and Pollard, 1988; Bursik and Sieh, 1989; tributing to the long-term growth of topographic Ebinger, 1996; Scholz and Contreras, 1998; Wright Wright et al., 2006; Rowland et al., 2007; Villamor relief and the structural development of the region. et al., 2006; Rowland et al., 2010; Muirhead et al., et al., 2011; Athens et al., 2016; Gómez-Vasconcelos In the eastern Sevier Desert, the intrabasin Tab- 2016). The underlying reasons for rift segmentation et al., 2017). The thinner effective elastic thickness ernacle, Pavant, and Deseret fault systems show comprise an interplay of modern strain rate, total of the crust in magma-assisted rifts means that markedly different surface expressions and behavior amount of cumulative strain, presence of inher- seismic strain release is localized on shallowly from the range-bounding normal faults farther west. ited structures, thermal and mechanical layering rooted (<5 km) faults associated with propagat- Pleistocene to Holocene extension rates on faults of the lithosphere, and melt availability (e.g., Buck, ing dikes. These faults do not usually accumulate in the eastern Sevier Desert are >10× higher than 1991; Brun, 1999; Corti et al., 2007; Nestola et al., elastic strain through a seismic cycle and do not

This paper is published under the terms of the those on their western counterparts. Faults here 2015). Depending on these factors, the mode of typically produce Mw ≥6 earthquakes (Parsons and CC‑BY-NC license. are co-located with Late Pleistocene to Holocene deformation within segments can vary with time; Thompson, 1991; Smith et al., 1996; Rowland et al.,

GEOSPHERE | Volume 16 | Number 1 Stahl et al. | Paleoseismic patterns of Quaternary tectonic and magmatic surface deformation Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/16/1/435/4920116/435.pdf 435 by guest on 29 September 2021 Research Paper

2007). In tectonic rift segments, or during episodes of limited melt supply, upper-crustal extension can 114°W 113°W 112°W 111°W

be accommodated entirely by tectonic faults that span the seismogenic portion of the crust (Rowland e

ID WY n et al., 2010; Medynski et al., 2016). Surface rupturing o

C Z A

earthquakes of Mw 7 or greater occur regularly on NV UT Roc ky t

tectonic normal faults, despite evidence for tem- Mts. l

Basin and u

poral variability in the length of the seismic cycle a Range F (e.g., Friedrich et al., 2003; Gómez-Vasconcelos and CO Wernicke, 2017). Given the disparity in maximum Colorado 40°N h magnitudes on dike-induced versus tectonic faults, Plateau c t distinguishing between the two is important for the AZ NM a s purposes of characterizing seismic hazard, espe- ORBT a cially if they are both present within the same rift W segment (Smith et al., 1996; Villamor et al., 2007; House Rowland et al., 2010; Villamor et al., 2011; Gómez- Range DM Sevier Fault Fig. 8 P106 Vasconcelos et al., 2017). Desert SPM Tectonic and magma-assisted rifting can be dis- HR FOOT TV SMEL CR tinguished based on the geometry, recurrence, and P103 P105 P082 GPS Transect Fig. 3 SPIC expression of active faults at the surface (Smith CnR et al., 1996; Rowland et al., 2007; Payne et al., 2009; Fig. 10 P104

Villamor et al., 2011; Gómez-Vasconcelos et al., lt 39°N SL u Lake a 2017; Stahl and Niemi, 2017). If magma-assisted F

. Bonneville s rifting is accommodated by dike intrusion, faults BH t CM BRDVF Max. M

t exhibit a spatial and temporal coincidence of fault- e Extent k c ri ing with volcanism, and are intermixed with mode (Bonnevile C I extensional fissures (cf. Smith et al., 1996; Payne Shoreline) ransition Zone et al., 2009). Compared to regions dominated by T Colorado Plateau tectonic faulting, there may also be discrepan- cies between geodetic and geologic extension estimates if some strain is accommodated aseis- mically (e.g., Smith et al., 2004; Wright et al., 2006). Elevation (m) 3000+ In contrast, the surface expressions of tectonic faults have displacement, length, and recurrence 38°N characteristics that roughly follow empirical scal- 1300 ing laws developed from catalogues of historical

surface-rupturing earthquakes (e.g., Wells and Cop- Figure 1. Overview of the Sevier Desert region, study sites, and transect location at the eastern margin of the Basin and Range persmith, 1994; Wesnousky, 2008), and geological province (inset) in central Utah (USA). The locations of Figures 3, 8, and 10 are indicated. The Wasatch fault zone (red) is commonly extension or moment estimates may be expected designated as the boundary between eastern Basin and Range and the Basin and Range–Colorado Plateau transition zone. The maximum extent of Late Pleistocene Lake Bonneville is shown in blue. Lake Bonneville was divided after water levels fell below to more closely align with geodetic and seismo- the Old River Bed threshold (ORBT) separating the Great Salt Lake and Sevier sub-basins. Light red shaded areas in the eastern logical estimates. Sevier Desert are Pliocene to recent volcanic rocks within the Black Rock Desert volcanic field (BRDVF; dotted outline). Black The Basin and Range of the western United lines are Quaternary faults and folds included in the U.S. Geological Survey Quaternary faults database (U.S. Geological Survey and Utah Geological Survey, 2006). UNAVCO Plate Boundary Observatory and BARGEN GPS stations used for the GPS transect States is one of the characteristic examples of a in this study are shown in yellow. Stations P106 and FOOT lie farther away from the transect and were therefore not used. State wide continental rift (terminology of Buck, 1991) abbreviations in inset: CA—California; NV—Nevada; ID—Idaho; UT—Utah; WY—Wyoming; CO—Colorado; AZ—Arizona; NM—New (Fig. 1). The mode of extension has not been uniform Mexico. Other abbreviations: CnR—Confusion Range; TV—Tule Valley; HR—House Range; DM—Drum Mountains; BH—Black Hills; through time or across this nearly 1000-km-wide SL—Sevier Lake; CM—Cricket Mountains; CR—Canyon Range; SPM—San Pitch Mountains. intraplate extensional province (Axen et al., 1993;

McQuarrie and Wernicke, 2005; McQuarrie and and the spatial distribution of extension and the ■■ GEOLOGIC BACKGROUND Oskin, 2010). Extension is currently dominated by mechanisms by which it is accommodated, par- tectonic faulting on range-bounding normal faults ticularly in the eastern Sevier Desert, are still Lake Bonneville and the Provo Shoreline that accommodate far-field, plate boundary–driven debated (Hammond and Thatcher, 2004; Niemi extension (e.g., Personius et al., 2017), with some et al., 2004; WGUEP, 2016; Stahl and Niemi, 2017; The evolution of Lake Bonneville underpins evidence at the western edge of the Basin and Yuan et al., 2018) (Fig. 1). Competing hypotheses the Late Pleistocene geomorphology of the Sevier Range for crustal extension being accommodated for strain accommodation across the Sevier Desert Desert. Exhaustive reviews by Oviatt (2015) and via intrusions in the crust (e.g., Bursik and Sieh, include slip on a buried low-angle normal fault, Oviatt and Shroder (2016, and references therein) 1989; Smith et al., 2004; Athens et al., 2016). the Sevier Desert detachment (e.g., Niemi et al., provide summaries of the >100 years of research The highest modern strain rates in the Basin and 2004; Yuan et al., 2018); salt tectonics and resul- on Lake Bonneville. Here, we provide an overview Range are concentrated near its margins (Bennett tant surface faulting (e.g., Wills et al., 2005); and of the information that is relevant for assessing et al., 2003; Hammond and Thatcher, 2004; Zeng magma-assisted rifting via episodic dike injection fault activity in the Sevier Desert area. and Shen, 2017). At the eastern margin of the Basin (Stahl and Niemi, 2017). Quantifying the relative Lake Bonneville was a Late Pleistocene pluvial and Range in central Utah, ~4 mm yr−1 of east-west contributions of magmatic and tectonic processes lake that covered >50,000 km2 of western Utah at extension is accommodated between the west- to extension in the Sevier Desert can help resolve its maximum extent. While Lake Bonneville was ern edge of the stable Colorado Plateau and the this debate, and the wealth of existing data make only the most recent major lake cycle in the basin Nevada border (Fig. 1). North of ~39°N, most of this the Sevier Desert an important natural labora- over the last 2 m.y., no evidence exists of an equiv- extension is accommodated on the Wasatch fault tory for resolving competing models of strain alent lake for tens of thousands of years prior to and associated structures (Friedrich et al., 2003). accommodation. its rise (Thompson et al., 2016). There were three The Wasatch fault, however, does not continue Following from a 2017 study (Stahl and Niemi, major phases of Lake Bonneville: (1) transgres- as a discrete structure south of ~39°N. Instead, a 2017), we hypothesize that late Quaternary extensive, (2) overflowing, and (3) regressive (Currey, diffuse north-south–trending boundary separates sion in central Utah (Fig. 1) is partitioned into 1990; Oviatt, 2015) (Fig. 2). The transgressive phase extended and non-extended domains to the south, magma-assisted and tectonic segments. To test (phase 1) began during cooler and wetter climatic highlighted by resistivity and tomographic surveys this hypothesis, we present new data on the Late that show the contrasting lithospheric structure Pleistocene to Holocene activity of active faults in a between the eastern Basin and Range, Colorado transect across the Sevier Desert (Fig. 1). We begin Plateau, and an intervening “transition zone” (Fig. 1) with a review of the late Quaternary geologic his- Transgressive Overﬂowing Regressive (Wannamaker et al., 2008; Schmandt and Lin, 2014; tory of the Sevier Desert, including previous work Bonneville Shoreline Liu and Hasterok, 2016; Long, 2018). that constrains the ages of Lake Bonneville high- 1550 Near the transition zone in the easternmost stands and volcanic landforms, which are essential Basin and Range, narrow zones of low resistivity geomorphic markers in this region, and an over-

within ~30-km-thick continental crust of the east- view of new geochronology data from this study 1500 Provo ern Sevier Desert (Fig. 1) coincide with regions of that bear on the ages of these features. The results Shoreline

high heat flow, Pleistocene–Holocene volcanism, from our fault studies across the Sevier Desert, 1450

and Pleistocene–Holocene faulting (Wannamaker including mapping, surveying, and geochronology, Lake et al., 2008, 2013; Liu and Hasterok, 2016; Stahl and are then presented by region. Time-integrated slip Adjusted lake altitude (m) Gunnison 1400 Niemi, 2017; Long, 2018). A thin lithospheric mantle and extension rates are calculated for the major PB TH IS? (~25 km) and a prominent low-velocity zone in the range-bounding and intrabasin faults of the west- underlying asthenospheric mantle at ~65 km depth ern and eastern Sevier Desert and compared to GPS 1350 24 20 16 12 Age (ka) (York and Helmberger, 1973; Levander and Miller, extension rates. The timing of most-recent events 2012; Schmandt and Lin 2014) are characteristic of (MREs) are estimated for select faults from 10Be and Figure 2. Hydrograph of Lake Bonneville fluctuations within the other volcanic regions of the Basin and Range and 3He exposure age dating of alluvial fans and tension Sevier Basin (blue) and timing of Late Pleistocene–Holocene volcanism (red). The simplified hydrograph of Lake Bonneville indicate favorable conditions for a continued, albeit fissures in basalt, respectively. We conclude with a is modified after Oviatt (2015). Where the age of volcanism is slow, supply of melt to the upper crust in this region new model of active tectonics in the Sevier Desert well constrained (Tabernacle Hill, TH; Pavant Butte, PB), the (e.g., Valentine and Perry, 2007). in which deformation is partitioned into domains timing is represented as a star. Where the age has uncertainty of thousands of years (Ice Springs, IS), the timing is represented Magmatic contributions to finite extension that are currently dominated by either tectonic or as a bar. See text and Figure 3 for references and further dis- have not been fully quantified in the Sevier Desert, magma-assisted extension. cussion of event timings.

conditions in Utah at ca. 30 ka. During this time, refined the age of the Provo shoreline to forming and shoreline elevations around the flow, Oviatt all water entering the basin exited via evaporation between 14.8 and 18.2 ka (Miller, 2016). We adopt (1991) interpreted the Tabernacle Hill flow as having only. Lake level rose to the elevation of the Bon- a simplified age range of 15–18 ka for the Provo erupted during the Provo highstand of Lake Bon- neville shoreline (Fig. 1), which was maintained by shoreline in this paper. neville. Subsequent sampling and dating of this the elevation of an alluvial fan dam near Red Rock tufa with procedures to avoid atmospheric contam- Pass, Idaho. Eventual breaching of the alluvial fan ination and using accelerator mass spectrometry caused catastrophic flooding that took place rapidly, Volcanism in the Black Rock Desert (AMS) revealed a slightly older age of 18.2 ± 0.3 with lake level lowering ~120 m in an estimated Volcanic Field cal. kyr B.P. (Fig. 2), uncorrected for a near-negli- ~500 yr (O’Connor, 1993; Janecke and Oaks, 2011; gible (~200 yr) reservoir effect in Lake Bonneville Miller et al., 2013). Following lake-level lowering, Bimodal volcanism in the Sevier Desert began at this stage (McGee et al., 2012; Lifton et al., 2015; there was sustained outflow of Lake Bonneville in the late Miocene, but has been most active since Oviatt, 2015). through the Snake River Plain for ~3 k.y. during the ca. 2.5 Ma (Johnsen et al., 2010). Here, we focus The largest flows (by exposed area) are those overflowing stage (phase 2) (Oviatt, 2015). During our overview on the geochronology of the Black of the Pavant field (Fig. 3). Two sub-flows within this stage, the prominent Provo shoreline formed Rock Desert volcanic field (e.g., Hoover, 1974; Oviatt, this field were mapped by Hoover (1974) (Fig. 3). around the Great Salt Lake and Sevier sub-basins 1991) in the eastern Sevier Desert (Figs. 1 and 3). Reported ages for both basalt flows range from of Lake Bonneville (Figs. 1 and 2). Most volcanic units mapped in the eastern Sevier 30 ± 69 ka to 220 ± 260 ka based on K-Ar dating Lake level fell during the regressive phase Desert are basalt and basaltic andesite lava flows (Condie and Barsky, 1972; Hoover, 1974; Best et al., (phase 3) after overflow ceased and the basin (Johnsen et al., 2010). In some cases, dacites and 1980; Johnsen et al., 2010) (Fig. 3). The Pavant I once again became hydrographically closed (Fig. 2). rhyolites are exposed at the surface in close prox- and II flows are spatially, but not temporally, coin- During this stage, Lake Bonneville segregated, and imity to larger basalt flows. There is no clear spatial cident with a volcanic edifice called Pavant Butte Lake Gunnison formed as a hydrologically sepa- or temporal progression in composition of the (Fig. 2). Pavant Butte was constructed later than the rate lake in the present Sevier Desert. Overflow volcanic units, although the youngest (Late Pleis- surrounding flows and was the source of the wide- from Lake Gunnison reached the lower Great tocene to Holocene) ashes and flows are basaltic. spread Pavant ash that can be found throughout the Salt Lake Basin to the north until Lake Gunnison A more detailed review of previous work, including eastern Sevier Desert (Oviatt and Nash, 1989). The dropped below the Old River Bed threshold and the ages, petrology, and chemistry of volcanic rocks in Pavant ash is relatively well constrained as having two basins became hydrologically disconnected central Utah, is provided by Johnsen et al. (2010). erupted into the late transgressive phase of Lake (Fig. 1). Continued regression of Lake Gunnison The youngest volcanic unit in the Sevier Desert Bonneville at 15.3–16 ka (Oviatt and Nash, 1989) (ca. likely occurred less rapidly than in the Great Salt is the Ice Springs basalt (Fig. 3). The Ice Springs 19 cal. kyr B.P., using IntCal13 curve and CALIB 7.10 Lake Basin, as inflow to Lake Gunnison from the basalt is commonly reported as being 660 ± 170 sotfware; Stuiver et al., 2019). Sevier and Beaver Rivers moderated losses due 14C yr B.P. or younger (Valastro et al. 1972; Oviatt, Among the oldest volcanic units in the study to evaporation from ca. 13 to 11.5 ka (Hintze and 1991; McBride et al., 2015). This age, however, is not area (Fig. 3) is the tholeiitic basalt of the Deseret Davis, 2003) (Fig. 2). During this time, Lake Tule (in considered robust, as it is based on dating a single volcano (Johnsen et al., 2010). This flow has pre- the Tule Valley adjacent to the House Range; Fig. 1) root fragment within a soil on the edge of one of viously been dated by Best et al. (1980), yielding became isolated from the rest of Lake Gunnison the four flow lobes (Valastro et al., 1972; Hoover, a K-Ar age of 400 ± 400 ka. Despite the large age and subsequently regressed rapidly due to limited 1974; Patzkowsky et al., 2017). Recent exposure age uncertainty, the Deseret volcano is known to be inflow (Sack, 1990; Hintze and Davis, 2003). and varnish microlamination dating suggests that pre–Lake Bonneville in age based on shorelines on The most important aspect of Lake Bonneville the Ice Springs flows could be significantly older— the edge of the flow (Oviatt, 1989) (Figs. 1 and 2). chronology for this study is the age of the Provo between 9 and 12 ka (Schantz, 2016; Patzkowsky Several other volcanic vents and small flows are shoreline. The Provo shoreline is well preserved et al., 2017) (Fig. 2). known in the eastern Sevier Desert, but are not radio- in many locations across the Sevier Desert, repre- The Tabernacle Hill flow is a basalt flow ~1 km metrically dated. In addition to the volcanic rocks sented by erosion into, or deposition on, lava flows south of the southern edge of the Ice Springs lava exposed at the surface, extensive subsurface basalt and eruptive vents, alluvial fan surfaces, and bed- flow (Fig. 3). Original dating of the flow was con- flows, some as old as 6.9 Ma, have been interpreted rock promontories. The shoreline formed over an ducted using tufa that was encrusted onto the outer in seismic lines across the eastern Sevier Desert ~3 k.y. interval from ca. 15 to 18 ka (Godsey et al., margin of the flow (Oviatt and Nash, 1989). This and correlated to adjacent well data (Lindsey et al., 2011; Oviatt, 2015; Miller, 2016). Miller et al. (2013) sample yielded a radiocarbon age of 14.3 ± 0.9 ka 1981; Planke and Smith, 1991). There are no known documented two Provo-aged shorelines at localities (ca. 17.3 ± 0.3 cal. kyr B.P). Based on this minimum Pliocene to recent igneous rocks west of the Cricket throughout the Bonneville basin. Subsequent work age for the flow, and on the presence of lava pillows Mountains in the western Sevier Desert (Fig. 1).

Previous studies This study, 40Ar/39Ar sample location and age Elevation (m) DesAR01: 3 668±9 ka Deseret This study, He exposure 1550+ Figure 3. (A) Overview of eastern Sevier 400±400 sample location 4 Desert faults, volcanic rocks, and sam- ka Pleistocene to recent volcanics ple locations. Purple shaded areas are Volcanic vent 1300 Pleistocene to recent volcanic rocks (pre- East-dipping fault dominantly basalt and andesite with some Clear Lake West-dipping fault rhyolite) either exposed at the surface or faults Pavant variably covered by a thin veneer of lacus- Butte trine and/or aeolian sediment (modified Deseret faults after Hintze et al. [2003] and Hintze and Davis [2002a]). Active faults are taken from U.S. Geological Survey Quaternary Fault Pavant II: ca. 30 ka5 and Fold Database (U.S. Geological Sur- vey and Utah Geological Survey, 2006) with dip directions modified by field mapping Fig. 5D where available. The names of lava flows Pavant DKF1: Fault and previous age constraints are shown in 758±21 ka white boxes; sample names and locations Pavant I: Fig. 6 for this study are shown with green and 30-220 ka5,6 Devil’s blue boxes (see Figs. 5 and 7). References Kitchen are as follows: 1—Lifton et al. (2015); 2— Oviatt (1991, after Valastro et al., 1972); ARAR5: 3,4—Best et al. (1980); 5—Hoover (1974); 6— Ice Springs 66±13 ka Condie and Barsky (1972); 7—Patzkowsky >0.6 ka2,3 et al. (2017). (B) Uninterpreted 5 m digital 9-12 ka7 elevation model and shaded relief over the same extent as A. Note that topography is dominated by prominent volcanic cen- Fig. 4 ters and, to a lesser extent, approximately Tabernacle north-south lineaments (faults) that cut Beaver Faults Ridge them. Clear Lake (depression in middle left) 500-1000 TH100- is represented as a constant value despite 5,6 TH201 ka having evidence of faults displacing the playa surface (see mapping in A). Tabernacle 18.2±0.3 ka1

■■ DATA AND METHODS approaches. Because our goal is to extract fault New Chronologic Constraints on the Volcanic displacement information from both of these types and Tectonic History of the Sevier Desert Our goal in data collection and analysis is to of information, we first summarize the geochrono- measure cumulative displacements across faults, logic methods we have used and the results we The methods and results of all of the age data fissures, and fold scarps in the Sevier Desert, have obtained. We then summarize the methods collected in this study are presented in Table 1. In determine single-event displacements (SEDs), we employed for obtaining high-resolution topog- three locations, we used 40Ar/39Ar to date lava flows and, where possible, estimate fault slip rates and raphy across the faults, and the assumptions and (e.g., the Deseret and Pavant I and II flows). For the timing of most-recent events (MREs). Because methods used to derive fault displacement infor- Tabernacle fault, we used 3He exposure-age dating fault-related deformation in the Sevier Desert mation from these profiles. The introduction of all in olivine to establish timing of fissure openings region transects a range of geologic materials and of these methods is followed by the integration of along one major trace of the fault (e.g., Mackey time scales, such an analysis requires the appli- fault slip and age data pertinent to specific study et al., 2014). For the House Range fault, we used cation of a variety of survey and geochronologic areas across the Sevier Desert. 10Be exposure-age dating to constrain the age of

TABE 1. SUMMARY O NEW GEOCHRONOOGIC DATA COECTED IN THIS STUDY eature Sample numbers Coordinates Method target Type of age Usage Age a Deseret lava flow DesAR01 39.20406N, 112.6661W 40Ar/39Ar groundmass Crystallization Etension rate across flow 668 9 Pavant I lava flow ARAR5 39.029925N, 112.49154W 40Ar/39Ar groundmass Crystallization Etension rate across flow 66 13 Pavant II lava flow D1 39.05612N, 112.50954W 40Ar/39Ar groundmass Crystallization Etension rate across flow 58 21 Tabernacle fissure top TH200, TH201 n 2 38.932385N, 112.524813W 3He olivine Terrestrial cosmogenic nuclide eposure Event timing: age of fissure opening 16.3 1.8 Tabernacle fissure bottom TH100, TH101 n 2 38.932385N, 112.524813W 3He olivine Terrestrial cosmogenic nuclide eposure Event timing: age of fissure opening 13.6 2.5 House Range, HR01–HR06; 39.38N, 113.39W 10Be uartz Terrestrial cosmogenic nuclide eposure Event timing: minimum age of most recent event ca.13.6–18.5 post‑Provo alluvial fan HRC1–HRC4 n 10 Note: Details on methodology and analysis are included in the Supplemental Information tet footnote 1 to this article. Isochron age. Plateau age. Modeled age; see individual sample details in the Supplemental Information.

an unfaulted alluvial fan that postdates the MRE and regressions fit to the hanging wall, footwall, We measured extension across fissures where not on the fault. Full methodological details, including and scarp, following the Monte Carlo simulation associated with fault traces, and added these values preparation, analysis, and modeling, are included methodology developed by Thompson et al. (2002). to the cumulative extension across studied fault in the Supplemental Information1. Further discus- From these slip estimates, we calculated cumula- zones. Fissures in lava flows are not likely to span sion of the results are provided for each of the faults tive extension and throw across each fault zone. the depth of the crust, and, given no local vertical separately in subsequent sections. In our calculations, we assumed that all motion is separation, likely represent the surface expression dip slip, as we observed no evidence of strike-slip of distributed dike-induced dilation at the surface. displacement in the field. We used input parame- In places where the ages of displaced land- Topographic Surveying and Calculation of ters and uncertainties for fault parameters deemed forms are known (Table 1), we also calculated slip Fault Slip appropriate for each fault based on our mapping, and extension rates using the same Monte Carlo subsurface data from other studies (e.g., Crone approach (Thompson et al., 2002), with ages and Method details High-resolution topography and fault displacements We conducted detailed geomorphic mapping at and Harding, 1984; Greene 2014; McBride et al., uncertainties constrained by age data in Table 1. select locations along faults using aerial imagery and 2015), and exposures (Table 2). Most near-surface SEDs are presented wherever they are evident. shaded relief derived from the 5 m digital elevation geophysical investigations and our observations Time-integrated slip rates are presented only models (DEMs) available from the Utah Automated show that all faults are steeply dipping (70°–85°) for faults where reliable SEDs can be estimated Geographic Reference Center (AGRC; https://gis.utah. within ~1 km of the surface, but, where available, across the entire fault zone (i.e., the House Range gov/data/). At the House Range, Cricket Mountains, we prefer moderate dips with conservatively large and Cricket Mountains faults). As these faults have and Tabernacle faults, we created high-resolution ranges to reflect average dip at depth from seismic long recurrence intervals relative to the age of dis- digital surface models (DSMs) generated from ter- reflection and interpreted geologic cross sections placed landforms, the slip rates we present depend restrial lidar scanning (TLS) and unmanned aerial (e.g., Allmendinger et al., 1983; Planke and Smith, on the time elapsed since the last event. To account

Geochronology system (UAS)–based structure-from-motion (SfM) 1991; Wills et al., 2005; Greene 2014). Where we for this effect, we assigned an additional slip rate acquisitions (details of acquisition and processing have limited or no data on where a fault projects uncertainty of 0.1 mm yr−1 to these faults following 3He exposure age dating are included in the Supplemental Information [foot- to the surface, we assume that the fault intersects the approach of Personius et al. (2017). μ note 1]). Topographic profiles of faulted shorelines, near the midpoint of the scarp (Table 2). Based fan surfaces, and lava flows were generated using on unpublished trench exposures in alluvial fans, field survey data from real-time kinematic (RTK) faults tend to project to the surface 50%–75% of the Paleoseismic, Geologic, and GPS Extension Global Navigation Satellite System (GNSS), the way up the scarp from the hanging wall in these Rates 5 m DEM, and TLS- and SfM-derived DSM products. deposits, and we use that range instead (Table 2). 1 Supplemental Information. Provides additional meth- Topographic profiles were used to calculate Monoclines were treated as fold scarps and have In order to investigate extension rate variabil- odology and laboratory data for field surveys and dip slip, considered to be the net slip, for each slip resolved on faults at depth, some of which ity, we compared our paleoseismic-time-scale slip rock samples. Please visit https://doi.org/10.1130 /GES02156.S1 or access the full-text article on www mapped fault trace. Net slip was calculated using have been identified in seismic lines and ground rate data to GPS and geologically derived exten- .gsapubs.org to view the Supplemental Information. estimates of fault dip, fault position along the scarp, penetrating radar surveys (McBride et al., 2015). sion rates. We used the horizontal component of

TABE 2. SUREY METHODS AND AUT PARAMETERS USED TO CACUATE SIP AND SIP RATE DISTRIBUTIONS ault zone Survey method ault dip ault proection along scarp Cumulative heave Offset feature Offset feature age upscarp from its base etension, m Tabernacle TS GPS DEM 60 10 50 10 13.2+3.2 Tabernacle Hill flow 18.2 0.3 a −2.0 Pavant GPS DEM 55‑80 50 10 29.1+4.9 Pavant II flow 58 21 a −4.9 Deseret GPS DEM 60 10 50 10 81.4+1.1 Deseret flow 668 9 −15. Clear ae GPS 60 10 50 10 .+1.6 Clear ae playa 10 5 a −1.6 Cricet Mountains TS 65 10 50–5 1.0 Provo shoreline 15–18 a House Range UAS 65 10 50–5 0.2 Provo shoreline 15–18 a Methods used to measure topographic profiles across fault scarps. TSterrestrial laser scanning; GPSreal‑time inematic GPS transects, which in places have been supplemented by a 5 m digital elevation model DEM; UASunmanned aerial system. Estimated mean values from our observations with normally distributed 2σ uncertainty or a uniformly distributed range. Mean and 95 confidence interval. alues with no uncertainty listed House Range and Cricet Mountains indicate that we selected a maimum value from the literature or our field measurements rather than a range of calculated net slips.

maximum net slip calculated in this study for pale- as existing geodetic velocities and paleoseismic stud- portion of extensional strain but are poorly preserved oseismic extension estimates to account for surface ies (e.g., Niemi et al., 2004). Below, we describe our due to lack of significant vertical separation and the slip deficits (e.g., Wells and Coppersmith, 1994; new mapping, surveying, and sampling strategies small scale of the features. Not all extension may Dolan and Haravitch, 2014; Personius et al., 2017). for each of these fault zones. Extension rates are be expressed as brittle deformation at the surface Geologic extension rates from the Clear Lake to the presented at the end of each section. It is important (Wright et al., 2006)—in analog experiments and Pavant faults in the eastern Sevier Desert are pre- to note that due to sedimentation through several geodetic inversions of dike-induced deformation, sented based on estimates from Planke and Smith Pleistocene lake cycles, Holocene dune deposition, extension accommodated by faults and fissures (1991), calculated by summing fault heave across a and the limited extent of radiometrically dated lava at the surface is usually less than dike thickness at 6.4 Ma basalt flow (Wills et al., 2005) imaged in seis- flows exposed at the surface, it is difficult to account depth (e.g., Mastin and Pollard, 1988; Hollingsworth mic sections, and assuming that the displacement for all of the extension in the eastern Sevier Desert. et al., 2013). Additionally, we only consider one-di- is not resolved on the Sevier Desert detachment. Numerous small fissures, such as those across Clear mensional extension (i.e., extension measured at We calculated GPS velocity profiles across the Lake playa and at Tabernacle Hill, accommodate a the surface in one direction) in adjacent transects. Sevier Desert using easting velocities from Basin and Range Geodetic Network (BARGEN) and TABLE 3. GPS VELOCITY DATA FOR THE SEVIER DESERT UNAVCO Plate Boundary Observatory stations in Station Easting velocity Direction Epoch Extension-only Extension velocity the NAM08 reference frame (available at https:// pair (mm yr−1) (1σ) (°) (yr) velocity difference difference uncertainty −1 −1 www.unavco.org/data/gps-gnss/derived-products (mm yr ) (mm yr ) (1σ)* /derived-products.html). GPS velocity solutions are SPIC- 2.30 ± 0.09 281 14.9 0.10 0.14 current as of December 2017. GPS velocity vectors are P105 2.40 ± 0.11 279 13.3 approximately perpendicular to average fault strike P105- 2.40 ± 0.11 279 13.3 –0.21 0.16 (~185°–190°) across this region, so we do not take into P104 2.19 ± 0.11 278 7.7 account northing velocities. Stations and the differ- P104- 2.19 ± 0.11 278 7.7 0.16 0.14 ential velocities between them are listed in Table 3. SMEL 2.35 ± 0.08 273 18.3 SMEL- 2.35 ± 0.08 273 18.3 0.16 0.15 P103 2.51 ± 0.13 274 7.7 ■■ PALEOSEISMICITY OF FAULTS WITHIN P103- 2.51 ± 0.13 274 7.7 0.09 0.17 THE BLACK ROCK DESERT VOLCANIC P082 2.60 ± 0.11 274 7.7 FIELD, EASTERN SEVIER DESERT Note: See Figure 1 for station locations. Data for each station are listed in each row; velocity differences and uncertainties therein are listed for each station pair. Epoch refers to the time period over We focused on four fault zones in the eastern which the GPS station has been continuously recording. *Errors summed in quadrature from station velocity errors. Sevier Desert that are at roughly the same latitude

In two- and three-dimensional strain, faults and fis- hanging wall of the west-facing fault. The lower Exposure ages of the fissure yield evidence of sures with <10 km length, as is typical in the eastern shoreline is marked by a zone of rounded boul- either one or two fissure-opening events caused Sevier Desert, may only accommodate ~20% of strain ders (P1, Fig. 4), and the upper is a wave-smoothed by faulting (Fig. 5). In the single-event model, three over geologic time scales (e.g., Cowie et al., 1993). platform (P2, Fig. 4). A single wave-smoothed plat- samples (TH200, TH201, TH101) are used to define a

form with rounded, CaCO3-encrusted boulders, and single E1 event, and sample TH100 is considered a an inferred wave-cut “inner-edge” carved into a younger outlier (see individual ages in the Supple- Tabernacle Faults tephra ridge, are present on the footwall of the fault mental Information [footnote 1]). This chronology (Fig. 4B). These correlative features are interpreted yields an error-weighted mean age of E1 at 15.9 The Tabernacle faults (Fig. 3) comprise a zone of to be Provo highstand shorelines (15–18 ka) based ± 1.8 ka (2σ). It is possible that the fissure was pro- faults, monoclines, and fissures developed in basalt on their elevation and age of the Tabernacle Hill gressively opened in more than one event, with across the Tabernacle Hill flow (Oviatt, 1991). Some flow. The lower shoreline on the hanging wall, P1, the top two samples having been exposed first. In lineaments included in the U.S. Geological Survey is displaced from the footwall shoreline by 10–12 this second scenario, in which all ages are accepted Quaternary fault database (U.S. Geological Survey m, which matches the ~10 m offset of basaltic ash and sample ages from opposite walls at the same and Utah Geological Survey, 2006) are actually fis- found to the north in the subsurface (McBride elevation are averaged, events E1 and E2 have sures that have a close spatial association with the et al., 2015). The upper shoreline, P2, is displaced error-weighted mean ages of 16.3 ± 1.8 and 13.6 central tuff cone within the flow (Stahl and Niemi, by 5–6 m relative to the footwall shoreline (Fig. 4). ± 2.5 ka, respectively (Fig. 5). The ages for these 2017). Faults have maximum vertical separations Based on mapping and survey results at this site, two events overlap within 2σ uncertainty, but are of 10 m and transition within 1–2 km along strike to two displacement events are interpreted on the distinguishable in a Kolmogorov-Smirnov test at tension cracks with no vertical separation. One of fault trace at this location. Event 1 (E1) occurred the 5% significance level. the fault traces is mapped across the Tabernacle Hill during initial development of the Provo shoreline A two-event displacement history is consistent flow (18.2 ka) and into the older Beaver Ridge flow (P1) on the flow edge, with 5–6 m of vertical sepa- with the observed offset of the Provo shoreline at (<1 Ma), potentially indicating continued displace- ration; E2 occurred after reoccupation of the Provo this site (Fig. 4), and we therefore favor the inter- ment or reactivation from mid-Pleistocene to recent shoreline (P2) across the fault, and accumulated pretation in which a minimum of two events have time (Fig. 3). At the northern end of the Tabernacle another 5–6 m vertical separation across the scarp. occurred on this trace of the Tabernacle fault since Hill flow, McBride et al. (2015) conducted active- We followed the sampling protocol and proce- the flow formed at ca. 18 ka, with 5–6 m of maximum source P- and SH-wave surveys across a horst and dure of Mackey et al. (2014) for dating the timing of vertical separation per event. Our data do not per- interpreted it to be bounded by a set of steeply these faulting events using cosmogenic exposure mit discrimination of several, closely spaced smaller dipping (~70°) faults. They also conducted augering ages to date fissure walls. The fissure selected is events that could have produced the observed ages, and found ash units (interpreted to be from Taber- developed within a monocline and therefore has nor can we rule out entirely the possibility that lake- nacle Hill) displaced vertically across the prominent an opening history linked to near-surface fault- level regression from the Provo shoreline at 16 ka west-facing scarp by 10.4 m (McBride et al., 2015). ing (Fig. 4B) (Mackey et al., 2014). There was no influenced the observed exposure ages. We do, how- We focused our paleoseismic study on the evidence of block toppling at the sites, and we sam- ever, consider the latter unlikely given the 3 k.y. age northern end of the Tabernacle Hill flow along a pled from locations on the fissure wall that could be difference between the upper and lower samples. prominent horst that projects northward to, and is visually reconstructed to the opposite fissure wall. We calculate cumulative horizontal extension buried by, the younger Ice Springs flow (McBride We collected four samples from the walls of the across the 5-km-wide Tabernacle Hill flow, from et al., 2015). This location was selected because fissure along the northern edge of the Tabernacle a combination of all faults and fissures, to be +3.2 it has the clearest expression of Provo shoreline Hills flow: two each from different fissure depths 13.2−2.0 m. Using an age of 18.2 ka for the flow (Lif- development around the flow edge (Fig. 4). The on opposing walls where there was no evidence ton et al., 2015), we calculate a minimum extension +0.19 −1 most continuous of the fault traces at this site is of block toppling, other erosion, or burial by sur- rate of 0.71−0.09 mm yr . west facing and forms a ~3-km-long monocline. face deposits. Samples were collected at >2.5 m Maximum vertical separation along the trace is depths to avoid inheritance from the flow surface. ~10 m; this value decreases to zero ~2 km to the Topographic and self-shielding was corrected for Pavant Fault south, where the monocline splays into a series by taking field measurements of the skyline geom- of fissures around the Tabernacle cone (Stahl and etry within the fissure and calculating a shielding Traces of the Pavant fault run from west of the Niemi, 2017). correction factor in CRONUS-Earth (Balco et al., Ice Springs flow to ~3 km south of Pavant Butte Mapping in the field and on a 1 m TLS DSM 2008). Analytical data are listed in Tables S1 and (Fig. 3). The fault traces trend NE to NW, including reveals two paleoshorelines preserved on the S2 (footnote 1). a ~60° bend (Fig. 3). The trace of the fault north

TLS Survey Extent Ice Springs D ca. 9-12 ka Vantage in C Flow edge 1

Flow edge 2 B P1 P2 Figure 4. The northern end of the Tabernacle Hill flow showing basic mapping and terrestrial lidar scanning (TLS) survey results. See Figure 3 for location. (A) TLS survey extent is overlain TH100-201 Provo on 5 m shaded-relief digital elevation model (DEM) with ages of Tabernacle and Ice Springs flows for reference. (B) Mapping of the Provo Tabernacle Hill shorelines (P1 and P2) and flow-edge features in ca.18.2 ka aerial photography and TLS shaded-relief DEM. Lines with bars and balls are normal faults (bar and ball on downthrown side). Samples TH100, TH101, TH200, and TH201 were taken from the Oblique aerial view (See W E location indicated. The vantage point of C— look direction in B) Topo 2 looking south at the fault scarp, shorelines, and Topo1 flow edge—is shown for reference. (C) Oblique Provo aerial perspective of TLS shaded relief showing locations of Provo shoreline(s) (P1 and P2, blue Topo 2 arrows) and topographic profiles drawn along and across them (black and yellow). 4WD—four- NO DATA Provo wheel drive. (D) Results of topographic profile P1 Topo1 P2 on 1 m TLS DEM showing two, 5–6 m vertical P2 separations on Provo-aged shorelines.

Wave cut P1 collapsed benches lava tube

4WD Track

125 250 500 meters N

of this bend comprises a west-facing scarp and/ the Pavant II lava and subparallel to the main zone, to evaluate evidence of syn- or post-Provo-aged or flexural monocline in columnar basalt. Vertical and another is identified 10–20 km to the northeast, displacement. For the assessment of deformation separation generally increases northwards along trending northeast (Fig. 3). rates, we obtained 40Ar/39Ar ages from the Pavant I the scarp from ~2 m in the south to a maximum Field work along the Pavant fault was focused and II lavas (after Hoover, 1974; Johnsen et al., 2010) vertical separation of >20 m in the Pavant II lavas, on constraining the timing of the MRE and assess- and conducted scarp surveys with RTK GPS sup- then decreases again or is buried closer to Pavant ing long-term extension rates by using 40Ar/39Ar to plemented with profiles extracted from a 5 m DEM. Butte. There are two locations where faulting is date the offset flows (Table 1). To determine the The excavation within fissure fill was conducted observed off of this main fault zone. A fault trace is timing of the MRE, we excavated a pit in fissure fill at ~1500 m above sea level (i.e., ~50 m below the identified 1 km to the west of the main trace within located within a monocline forelimb along the fault Bonneville and ~50 m above the Provo shorelines;

Looking north E1: 16.3 ± 1.8 ka 1 event model E2: 13.6 ± 2.5 ka (3 ages, 1 outlier): 15.9 ± 1.8 ka 2 event model (E1 event) TH100 ~2 m TH101 2 event model TH200 (E2 event)

Normal kernel density estimate TH201 TH100 TH101

Age (ka)

Figure 5. Field photograph of 3He exposure-age sample locations and resulting age models. (A) Photograph taken from fissure bottom with the locations of samples TH100 and TH101 indicated (location in Figs. 3 and 4). Samples TH200 and TH201 are ~2 m higher and south from this photo location. (B) Age models for the four samples and event ages based on two different scenarios. In a single-event scenario, we exclude the youngest sample age (TH100, ca. 12 ka) as an outlier and use the oldest three sample ages to obtain an event age of 15.9 ± 1.8 ka (thick red line). In the two-event model, samples are grouped by their location along the fissure wall. The two resulting event ages are 16.3 ± 1.8 and 13.6 ± 2.5 ka (thick blue lines). See text and Tables S1 and S2 (text footnote 1) for details.

Fig. 2) within an ~20-m-wide fissure (Fig. 6). The proposed relative age relationships and K-Ar ages had ~100% uncertainties. As such, we recom- 1.7-m-deep pit revealed basaltic lapilli at the base (Table 1; Fig. 3). Previous studies designated the mend adopting these new ages for the Pavant overlain by in situ lacustrine marl, silt, and sands Pavant I lava flow as being older than the inset flows. These new results require that the Pavant that were in turn overlain by aeolian sand (Fig. 6). and topographically higher Pavant II flow (Hoover, II lava, previously considered to be younger than The basal basaltic ash–lacustrine sequence is inter- 1974; Johnsen et al., 2010). Our analysis indicates the Pavant I lava, is more than an order of magni- preted to represent the end of the transgressive that samples from both flows have extremely low tude older. In a relative sense, the morphologies phase of Lake Bonneville, with the lapilli likely radiogenic yields (40Ar*), and so a trapped atmo- of the Pavant I and Pavant II flows do suggest that being sourced from the Pavant ash erupted from spheric initial 40Ar/36Ar value was assumed in age this is accurate—the Pavant II flow surface appears nearby Pavant Butte (Figs. 2 and 3) (Oviatt and Nash, calculations determined from plateau analysis. more modified, wavy, and oxidized than that of 1989). In this interpretation, the overlying marl and The plateau age (n steps = 8) for the Pavant I lava Pavant I. The map pattern that led to the original lacustrine sediments must date to the Bonneville from sample ARAR5 is 66 ± 13 ka (1σ) (Fig. 7B). interpretation (i.e., Pavant II flows “inset” within highstand at ca. 18.5 ka, and would imply that this Sample DKF1 from the Pavant II lava yields a pla- Pavant I) could be explained by the Pavant I lava fissure was open well before the Provo shoreline teau age of 758 ± 21 ka (Fig. 7C). Sample ARAR5 flowing around and filling depressions adjacent to had formed. While we cannot rule out post- or syn- yielded a disturbed age spectrum and has a high the much older, and locally thicker, Pavant II lava Provo events, no evidence has been found (e.g., a value of mean square weighted deviates (MSWD) flow (Fig. 3). buried layer of basalt colluvium from scarp col- at 10.6 (Fig. 7B). Sample DKF1 has a MSWD of 1.7, Despite the ~600 k.y. age difference, there is lapse) for such events at this site. There is, however, below the commonly accepted maximum value not a significant difference in the cumulative ver- strong evidence from the stratigraphy of the fissure of 2.5, and a relatively straightforward spectrum tical separation across the Pavant fault on these fill that this fissure was open pre-Provo and proba- with ages plateauing at ca. 0.75 Ma (n steps = 6) in two flows. The maximum vertical separation of the bly pre-Bonneville highstand. higher-temperature steps. Pavant I lava is 18 m. Maximum vertical separa- Further, new 40Ar/39Ar ages for the Pavant lavas We consider both of the new 40Ar/39Ar ages to tion on the same fault trace where it displaces the (this study) demand reevaluation of previously be improvements upon existing K-Ar ages, which Pavant II lava is on the order of ~20 m. Thus no, or

at most very little, displacement occurred on the Looking East Pavant fault prior to extrusion of the Pavant I flow, 0.0 m which suggests late-stage development of the fault Flow top / top of scarp trace through both flows. Qes 10.5 Y 6/4 Finely bedded sand and silt, calcareous with fragmented ooids Using the cumulative extension across the and gastropods Pavant II flow surface, which has greater poten- C tial for preservation owing to its higher position in the landscape and better age control, we calculate 29.1 ± 4.9 m of extension in the last 758 ± 21 k.y. Qlf This leads to a minimum extension rate estimate 10.5 YR 8/1 Sandy silt with of ~0.04 ± 0.01 mm yr−1. Using the more uncertain Location of discontinuous bands of marl, Qlm/Qlf ash, and gastropods pit in B age of the Pavant I lava in the calculation yields an extension rate estimate of 0.46 ± 0.13 mm yr−1. In Qlm/Qvb Qvb our summary of extension rates (below), we use −1 1.7 m the minimum rate of 0.04 mm yr .

Inside edge Looking North pictured in A Deseret Faults Fissure fill in B & C Basalt flow top Numerous west- and east-dipping faults displace the Deseret flow into a series of horsts and grabens. Between 12 and 20 fault traces, depending on location along the flow, displace the Deseret Basalt flow top basalt flow by up to ~20 m (Stahl and Niemi, 2017) (Fig. 3). The displacement histories on these faults were interpreted by Oviatt (1989) to predate Lake Bonneville, based on the observation that Bonne- ville sediments overlie the Deseret fault scarps. However, there are no established MRE timings on any of the fault traces. Faults that offset the flow surface do not disrupt the surrounding playa floor, although the adjacent Clear Lake fault scarps and fissures do displace the modern playa surface, and the westernmost Clear Lake scarp forms the edge of the Deseret flow (McBride et al., 2015) (Fig. 3). The Deseret flow has previously been K-Ar dated to 0.4 ± 0.4 Ma. We sampled the flow interior for 40Ar/39Ar geochronology to revise this age estimate. Sample DesAR01 had a low radiogenic yield, although high-temperature steps reached 15% yield. Figure 6. Trench exposure of a fissure developed in the forelimb of a basalt monocline along the Pavant fault. Location is During analysis, an excess trapped argon compo- shown in Figure 3. (A) View looking eastward at the fissure “inner edge” and toward the top of the fold. Backpack (~70 nent was suggested by a high 40Ar/36Ar value of cm; at lower right) shown for scale. (B) Trench stratigraphy. Units: Qes—eolian sand; Qlf—lacustrine fine sand and silt with ooids and fragmented gastropods; Qlm—lacustrine marl; Qvb—basaltic lapilli ash. (C) Zoomed section showing the contact 299.7 ± 0.2, and a reliable plateau age could not be between the two lacustrine units, interpreted as being from the transgressive phase of Lake Bonneville based on position reached (Fig. 7A). The isochron (“errorchron”) age in the landscape. This interpretation means that the fissure was open and had accumulated significant extension prior is therefore the preferred age for sample DesAR01 to 20–30 ka. Green flagging tape pinned to the trench wall indicates contacts between interpreted units. (D) Along-strike view of an ~20-m-wide sand-filled fissure developed in a basalt monocline on the Pavant fault. Schematic sketch shows at 668 ± 9 ka (1σ) with a MSWD of 9 (Fig. 7D). This the geometry of the fissure developed within the basalt monocline and locations of A, B, and C within that interpretation. MSWD value is significantly larger than commonly

and Harding, 1984; Oviatt, 1989; Planke and Smith, Deseret Flow: DesAR01 Pavant (south) Flow: ARAR5 Pavant (north) Flow: DKF1 1991). Others have questioned this interpretation (e.g., Wills et al., 2005). Currey (1982) considered that the Clear Lake fault zone may be related to sub- sidence into a magma chamber at depth, potentially related to adjacent Pleistocene volcanism. Because the Clear Lake faults do not displace any lava flows, and subsurface information is limited, we cannot fully address the recent activity of these faults in this study. We calculated net extension of 7.7 ± 1.6 m across the Clear Lake playa, which cuts surficial strata with an estimated age of 10 ± 5 ka (McBride et al., 2015; Stahl and Niemi, 2017). This leads to a minimum +0.78 −1 extension rate estimate of 0.77−0.29 mm yr .

■■ PALEOSEISMICITY OF FAULTS IN THE n WESTERN SEVIER DESERT

We focus on two major, range-bounding faults in the western Sevier Desert, the House Range and Cricket Mountains faults (locations in Fig. 1). Mapping and surveying (Bunds et al., 2019; this study) were conducted to constrain the displacement and timing of surface-rupturing earthquakes. In the House Range, we used 10Be exposure age dating coupled with a new modeling procedure to 40 39 Figure 7. Ar/ Ar step-heating and isochron results for the Deseret and Pavant I and II flows. (A–C) Top two plots indicate the constrain the age of a Late Pleistocene–Holocene percent of 40Ar (upper) and K/Ca (lower) released in each step. Bottom plots are step-heating results, with plateau, isochron, and integrated ages reported where calculated. (D) Isochron age (errorchron) for sample DesAR01, which is preferred due to the ele- fan surface, the formation of which postdates the vated 40Ar/36Ar initial values. See Table S3 (text footnote 1) for details. MSWD—mean square weighted deviates. Int.—intercept. last surface-rupturing event. Extension rates are estimated for both faults in order to compare with rates across the eastern Sevier Desert faults. accepted values (<2.5), but is considered a useful vertical separation across the zone is negligible improvement upon previously reported ages for (Stahl and Niemi, 2017). There is little subsurface the flow. information on most of this complex zone of fis- House Range Fault Net extension from normal faulting across the sures and faults, although the westernmost scarp, +17.1 668 ± 9 ka flow is81. 4−15.7 m. We therefore obtain with 4 m maximum vertical separation, has been The House Range fault is an ~37–50-km-long extension rates across the Deseret flow of 0.12 imaged via seismic reflection at various depths, west-dipping normal fault located on the western ± 0.03 mm yr−1. with progressively larger displacements on older side of the House Range (Figs. 1 and 8). For most strata (Crone and Harding, 1984; Planke and Smith, of its length, the surface trace is concealed and the 1991; McBride et al., 2015). McBride et al. (2015) fault’s surface projection is mapped as an inferred Clear Lake Faults inferred ~10 m of post–Lake Bonneville vertical sep- trace along the gravity anomaly at the boundary aration on this fault trace. Some have noted that between the structurally controlled Tule Valley basin The Clear Lake faults comprise a 5–10-km-wide, this fault can be traced to a prominent reflector at and the steep western escarpment of the House ~35-km-long zone of faults and fissures between the depth, and may therefore be kinematically linked Range (Hintze and Davis, 2003). At depth, the fault Deseret and Pavant lava flows (Fig. 3). Cumulative to slip on the Sevier Desert detachment (Crone is well imaged in seismic-reflection profiles and is

HR05 HR04

HR01 HRC1-4 HR02 Figure 8. Overview of the geomorphology and sample sites along the House Range fault. (A) Aerial photo with 10Be sample site locations. White arrows point toward the prominent fault trace that displaces shorelines shown in B and C. (B) Uninter- preted structure-from-motion 6 cm digital surface model on which mapping and HR05 fault displacement measurements were conducted. White arrows demarcating a HR06 prominent fault trace are shown for reference between panels A and B. (C) Portion of mapping within the survey area. Units:

Qla1—Pre-Bonneville alluvial fan with transgressive, Bonneville, and Provo shorelines Bonneville developed at the surface; Qla —Pre-Provo Bench 2 alluvial fans with significant regrading at the surface, obscuring most shoreline features; Qaf—Post-Provo alluvial fans. Area in C

Remnant fault scarp

Qaf: Post-Provo alluvial fans

Qla2 Qla2: Pre-Provo alluvial fans with Qla1 signiﬁcant regrading

Qla1: Pre-Bonneville alluvial fans Qla1 Pr with preserved lacustrine mantle ov o Local, recent sedimentation Be Qaf nch Normal fault Qaf Provo highstand tufa N 0 100 200 400 600 Meters Provo highstand bench

shown to be high-angle through the upper 5 km of drop may have caused concurrent progradation of deposits (unit Qla1), as represented by the suite of

the crust and listric below that depth, soling into post-Provo alluvial fans to the new Tule Valley floor transgressive shorelines (Fig. 8). Unit Qla1 surfaces the Sevier-aged Canyon Range thrust (Allmendinger over a short time period. The ages of these fans, if have local resurfacing and bar-and-swale topogra- et al., 1983; Greene, 2014). It is unclear if the House undeformed, would then tightly constrain the age of phy, but channel density is low and channels are Range fault extends to the south between the Black the MRE to between the ages of the Provo shoreline typically spatially limited to elevations below a Pro- Hills and southern Confusion Range, where the east- and the ages of the post-Provo alluvial fans (Fig. 8). vo-aged tufa zone (Fig. 8).The second-oldest fan

ern edge of Tule Valley is still structurally controlled Geomorphic mapping was carried out to supple- surface is unit Qla2, which is post–Provo highstand by a Cenozoic listric normal fault (Greene, 2014). ment past surficial mapping and to target sample in age as indicated by poor preservation of lacus- Evidence of late Quaternary activity is only sites for dating the MRE on the House Range trine deposits and shorelines due to deposition

present along ~10 km of the central section of the fault. Mapping was conducted on a combination of younger alluvium over the unit Qla1 surface. In

fault (Fig. 8). Here, the fault displaces pre–Lake of National Agriculture Imagery Program (NAIP) places, unit Qla2 has remnant shorelines preserved Bonneville alluvial fans, pre–Bonneville highstand aerial photography and a high-resolution DSM pro- due to the variable amounts of post-Provo aggra- transgressive shorelines, and the Provo shoreline duced from photogrammetry (Bunds et al., 2019). dation that took place across the surface (Fig. 8).

(Sack, 1990; Hintze and Davis, 2003). Piekarski (1980) The UAS-based photogrammetry encompasses ~6 In a single location on unit Qla2, there appears to 2 performed scarp diffusion dating along this sec- km and images the House Range fault, multiple be a window into the underlying unit Qla1 surface, tion of the fault from 23 fault scarp profiles and shorelines, and pre-Bonneville and post-Provo allu- and a degraded fault scarp is preserved (Fig. 8B).

estimated that the fault scarp formed more than vial fans. These high-resolution aerial imagery and Channel density is higher on unit Qla2 than on

12,000 yr ago, with an average vertical separation DSM products enhance the detail of geomorphic unit Qla1, and bar-and-swale relief is lower. The of 1.4 m. It was unclear from previous mapping (1) mapping over previous efforts. youngest fan surface is unit Qaf, which consists of whether the fault deforms post-Provo alluvial fans The House Range fault displaces both the trans- post-Provo alluvial fans with the highest observed or (2) if the Provo shoreline and older transgressive gressive shoreline sequence (estimated to have channel density, low bar-and-swale relief (<~1.5 m), shorelines are displaced by the same or differing formed at ca. 20 ka in Lake Tule; Sack, 1990) and and no preservation of lacustrine deposits. Units

amounts (i.e., that the average vertical separation the inset Provo shoreline at ~1462 m (Fig. 8). Ver- Qaf and Qla2 are unfaulted in the study region, and of Piekarski [1980] was calculated from a single or tical separations range from ~0.4 m to 1.5 m and the distinction between the two is made solely on multiple events). Sack (1990) and Hintze and Davis can vary by up to 1 m over distances of ~250 m on geomorphic grounds. (2003) proposed that regression from the Provo features of the same age (e.g., the Provo shoreline Net slip estimates at 18 locations along the shoreline took place rapidly in the Tule Valley due bench). The fault interacts with fan surfaces of three House Range fault vary between ~0.5 and 1.7 m to little inflow following the isolation of Lake Tule different relative ages, based on their morphology. (Fig. 9), with a mean of 0.95 m. Transgressive shore- from the rest of the Lake Gunnison (Sevier) basin. If The oldest fan unit comprises pre-Bonneville allu- lines young with increased elevation, and there is this is the case, the relatively rapid, local base-level vial fans with a preserved mantle of lacustrine no systematic increase in net slip with shoreline

1 1 Shoreline Figure 9. Overview of net slips calculated Pre-Provo along the House Range fault. (A) Probability density function (PDF) of net slips as cal- Alluvial fan culated in a Monte Carlo simulation from places along the Provo shoreline. (B) PDF of time-averaged slip rates using the Provo shoreline as the strain marker. (C) Summary of net displacements calculated along the House Range fault within the survey area. Error bars shows the 95% confidence interval of net slip distributions for each offset marker. Dashed line is the average net slip for all markers. Net slips are ~0.5–1.7 m, Relative Probability Density

Relative Probability Density but there is no systematic variation with 0 0 marker age or elevation, indicating that the variability is from natural or along-strike 0.6 0.8 1.0 0.03 0.05 0.07 variation. Provo Shoreline Net Slip (m) Maximum averaged slip rate (mm/yr)

marker elevation. In fact, some of the smallest val- and isolation of Lake Tule from other sub-basins of between formation of the Provo shoreline and for-

ues of net slip are from a pre-Provo unit Qla1 fan Lake Bonneville. mation of post-Provo-aged fans. surface below the level of preserved shorelines. Based on all of the new data, the House Range Mapping of the Cricket Mountains fault was con- Because similarly small slips can be measured on fault has experienced one surface-rupturing earth- ducted on NAIP aerial photography and a 1 m TLS both the Provo shoreline and transgressive shore- quake in the last 20–30 k.y., and this earthquake DSM (Fig. 10). The age of unit Qaf on the western lines above the Provo level, we attribute the range occurred soon after regression of then–Lake Tule slope of the Cricket Mountains is more difficult to of net slip to along-strike variability in surface dis- from the Provo shoreline. It is considered likely that constrain than in the House Range. Unlike in Tule placement over this short (~3 km) section of fault. the event occurred soon after 18.2 ka, between the Valley, inflow from the Beaver and Sevier Rivers in The best indication of a time-integrated slip rate minimum age of formation of the unit Qaf surface the eastern Sevier Desert kept Lake Gunnison levels is given by the displacement of the Provo shore- (ca. 13 ka) and the maximum age of the Provo relatively high throughout the Late Pleistocene and line, which yields a maximum slip rate since Provo shoreline (ca. 18 ka). Holocene (Hintze and Davis, 2003). Therefore, there time of 0.05 ± 0.12 mm yr−1, including the additional We used the maximum net slip at the surface to is no expectation that the formation of unit Qaf was epistemic uncertainty of ±0.1 mm yr−1 (Personius calculate an estimate of extension. Thus, the House related to rapid regression from the Provo shore- et al., 2017). Range fault has accumulated ~0.72 m of extension line; it more likely formed at various times along The ages of undeformed, post–Provo highstand since ca. 15–18 ka (age of the Provo shoreline), the range front, as Lake Gunnison slowly regressed

alluvial fans (units Qaf and Qla2, Fig. 8) would con- which yields an extension rate estimate of ~0.04 from the Provo shoreline and receded to the extent strain the minimum age of faulting on the House ± 0.02 mm yr−1 since that time. of the modern-day Sevier Lake (Figs. 1 and 2). Range fault. We collected six samples from Pros- Our TLS scan captures the displaced Provo pect Mountain quartzite boulders embedded in unit shoreline clearly (Fig. 10), but the resulting DSM

Qaf and Qla2 surfaces and four whole-clast samples Cricket Mountains Fault is of limited use in defining the transgressive shore- from an active dry wash. Individual boulder 10Be lines due to locally low point density. Just outside surface-exposure ages vary between ca. 28 and 137 The Cricket Mountains fault is an ~40–55-km-long the scan perimeter (Fig. 10), a unit Qaf surface was ka (Table S4 [footnote 1]) with a mean of ca. 63 ka. west-dipping normal fault on the western side of observed in the field to be undeformed by the fault. Samples HRC1–HRC4 (whole-clast samples taken the Cricket Mountains (Fig. 1). The observed sur- Net slip was calculated as 0.55 m on the upper unit

from the dry wash), which were originally collected face expression of faulting is limited to 40 km of Qla1 surface and 0.73 m on the Provo bench, with to provide an estimate of inheritance (as theoreti- this length, while the full extent of the structure the two being indistinguishable within uncertainty.

cally recently exposed clasts; e.g., Owen et al., 2011), is inferred from both topographic relief and struc- Using an age range for the unit Qla1 surface that instead yielded a broad range of exposure ages tural relief estimated from gravity surveys (Case spans from the youngest age of the Provo shoreline between 43 and 85 ka, and were older than some and Cook, 1979; Hintze and Davis, 2003). The Cricket (15 ka) to the oldest potential ages of transgressive clasts from the fan surface. Given that there is defin- Mountains fault has been inferred to sole into the shorelines (30 ka) yields a time-integrated slip rate itive geomorphic evidence that the unit Qaf fans are reactivated Canyon Range or Pavant thrust within at this site of ~0.03 ± 0.12 mm yr−1, which includes younger than the Provo shoreline (Sack, 1990; Hintze ~5 km below the surface (Allmendinger et al., 1983; additional epistemic uncertainty of ±0.1 mm yr−1. and Davis, 2003; Fig. 8), all of the surface exposure DeCelles and Coogan, 2006). Based on mapping and surveying at this sin- ages from the fan boulders and clasts must carry Previous workers have reported a maximum gle location, the Cricket Mountains fault’s MRE is significant and variable amounts of inherited cos- vertical displacement of the Provo shoreline of constrained to be post- or syn-Provo in age. Hecker mogenic 10Be. Therefore, even taking the minimum between 1.3 m (Hecker, 1993) and 2–2.4 m (Oviatt, (1993) considered the MRE to have occurred before clast age (28.01 ± 2.70 ka) is not tenable. 1989; Ertec Western Inc., 1981) across the fault. On ca. 8 ka, however this number is based on scarp While we cannot tightly constrain the age of the the southern section of the fault, Hintze and Davis diffusion modeling and subject to significant uncer- unit Qaf surface, preliminary modeling of expo- (2002b) mapped a fault trace that apparently dis- tainty. Similar to the House Range fault, there is no sure ages (after Oskin and Prush, 2015) suggests places a post-Provo alluvial fan. We found this trace evidence at this location of more than one event

that the resurfacing of unit Qla1, and deposition of to be present where mapped, but determined that occurring since the formation of the transgres-

units Qla2 and Qaf, likely occurred soon after final it is preserved on a degraded remnant of pre-Bon- sive-stage shorelines. regression from the Provo level sometime between neville fan where that remnant grades laterally Based on our data, we confirm that the Provo

ca. 13 ka and 18 ka (Fig. S1 [footnote 1]). This is into a younger fan surface (similar to unit Qla2 in shoreline is displaced and that previously reported consistent with a purely geomorphic interpretation the House Range). Nowhere else are post-Provo displacements across it are reasonable. Accepting that lake-level drop in the Tule Valley took place rap- fans obviously displaced by the Cricket Mountains the minimum age of the Provo shoreline as the idly following regression from the Provo shoreline fault, constraining the last event to have taken place last reliably dated strain marker, and the reported

maximum vertical separation of 2.4 m, we calculate 1.0 m extension on the Cricket Mountains fault over last 15–18 k.y. This leads to an extension rate estimate of ~0.06 ± 0.02 mm yr−1.

Figure 10. Terrestrial lidar scanning (TLS) TLS extent survey (top) and geomorphic map (bottom) ■■ DISCUSSION of the Cricket Mountains fault. White arrows demarcating the fault trace are shown Two faulting domains can be distinguished for reference. 4WD—four-wheel drive. across the Sevier Desert on the basis of surface expression, extension rate, and paleoseismicity. The first domain is defined by characteristics associated with faults, folds, and fissures found in the Black Rock volcanic field, which we will refer to as Qaf: Post-Provo alluvial fans Qlm: Lacustrine white marl the eastern domain. The western domain is defined Qlm Qla (exposed) by fault characteristics associated with the House 1 l Qlg: Lacustrine gravel

Range and Cricket Mountains fault. l

l Qlg Qla1: Pre-Bonneville alluvial fans

with preserved lacustrine mantle

ch n l e

B Transgressive (Pre-

o v Bonneville) shoreline Eastern Domain o r P l TLS extent Local sedimentation

Transgressive

4WD track Intrabasin faults of the eastern domain (Deseret, shorelines l Cpm

Normal fault

Clear Lake, Pavant, and Tabernacle faults) are spa-

Bonneville Bonneville highstand bench

tially coincident with Plio-Pleistocene volcanic Qla1 l Bench

edifices. Surface deformation is expressed as a Provo highstand bench

combination of basalt escarpments, monoclines,

Qaf Escarpment (ticks on riser) tension cracks, and fault scarps similar to morphol- l ogies observed the Volcanic Tableland of California (Ferrill et al., 2016). Individual fault zones are ~5 km wide; however, the zones together comprise a extension rates across the eastern Sevier Desert et al., 2003; Pérouse and Wernicke, 2017), with broader trend of surface deformation that is 15–20 faults are high (~0.1–0.8 mm yr−1) relative to faults higher Pleistocene–Holocene slip rates reflecting km wide (Fig. 3). Within this domain, individual fault in the western Sevier domain (< 0.1 mm yr−1), and short-term earthquake clustering. In the eastern traces are short (commonly <5 km) despite having were particularly elevated in the Late Pleistocene Sevier Desert, slow (or negative) modern exten- several meters of cumulative, on-fault displacement and early Holocene compared to geodetic and lon- sion rates (−0.1 to 0.1 mm yr−1) and late Miocene over 103 to 105 yr time scales. Faults generally exhibit ger-term geologic extension rates (Fig. 11). to recent geologic extension rates (0.19–0.35 mm greater cumulative extension and larger vertical There are a few possible explanations for the dis- yr−1) are similar, but are significantly lower than Late separations on older volcanic units, indicating recur- crepancy between paleoseismic extension rates and Pleistocene to Holocene rates on the Tabernacle and rent motion over the last ~0.75–6.5 m.y. (e.g., Wills those derived over other (e.g., geologic and modern) Clear Lake faults (~0.74 mm yr−1) (Fig. 11). et al., 2005) on at least some fault traces. time scales in the eastern domain. One possibility is Faster Late Pleistocene to Holocene extension Despite recurring activity and low sedimenta- that the geologic extension rate (0.19–0.35 mm yr−1; rates on the Tabernacle and Clear Lake faults may tion and erosion rates, most topographic relief in Fig. 11) represents a temporally averaged mixture of be the result of a transient episode of strain release the eastern Sevier Desert is produced by the vol- extension rates that vary on shorter time scales (e.g., driven by recent volcanism and associated defor- canic centers rather than faults. Offsets that arise Friedrich et al., 2003; Niemi et al., 2004; Pérouse and mation (Smith et al., 2004; Rowland et al., 2010; from displacement on individual fault traces are Wernicke, 2017). Elsewhere in the Basin and Range, Acocella and Trippanera, 2016). If this hypothe- either countered by displacement on antithetic where late Quaternary magmatism is not present sis is correct, faulting would be not only spatially faults or recovered over short fault-normal dis- or recognized, there is evidence for time-varying coincident with volcanism, but temporally clustered tances (Stahl and Niemi, 2017). Minimum on-fault strain accumulation as well as release (Friedrich during periods of dike intrusion into the upper crust.

There is some paleoseismic evidence that supports Figure 11. Summary diagram of differential this relationship: two events on the Tabernacle fault GPS extension rates (filled circles, values relative to station SPIC), individual fault ex- occurred during or soon after emplacement of the tension rates (squares), and two estimates 1.5 Fault extension rate

Tabernacle Hill flow, with no observed paleoseismic of cumulative fault extension rates across ) activity after emplacement of the undeformed Ice the transect shown in Figure 1. Pv—Pavant, –1 GPS extension rate Tb—Tabernacle, CL—Clear Lake, De—De- Springs flow at ca. 9–12 ka (Figs. 2 and 3). The Clear seret, CM—Cricket Mountains, HR—House Cumulative paleoseismic extension Lake fault zone does not directly coincide with vol- Range. Long-term geologic extension rate 1 (Clear Lake and Tabernacle canism at the surface, but is bounded on either side across the Clear Lake region is recalculated included) based on (1) the extension estimate of by the Deseret, Ice Springs, and Pavant lavas (Fig. 3). Planke and Smith (1991) that excludes slip CL Tb Cumulative paleoseismic extension Other models of active faulting in the eastern on the Sevier Desert detachment, and (2) up- (Clear Lake and Tabernacle Post-6.44 Ma 40 39 0.5 Sevier Desert have been proposed. Salt mobility dated Ar/ Ar age dating of a subsurface excluded) extension rate basalt used to make the original extension and saline fluids may play a subordinate role in calculation from Wills et al. (2005). There is SMEL De assisting faulting (e.g., Yuan et al., 2018), but there P082 agreement between the geologic (Pliocene Extension rate (mm y r P105 is no evidence of a direct influence from salt tec- to recent; Planke and Smith, 1991; Wills et al., SPIC 0 P103 CM tonics in our limited paleoseismic data set. Faulting 2005), paleoseismic (Pleistocene to recent), HR Pv (min.) and modern GPS extension rates when ex- P104 due to salt dissolution is characterized by short and tension rates from the Tabernacle and Clear Lake faults are excluded from the analysis. In erratic recurrence intervals (Guerrero et al., 2015), 0 40 80 120 and a strong temporal correlation between faulting contrast, paleoseismic fault slip rates exceed geodetic rates by >1.4 mm yr−1 when these Distance along transect (km) and volcanism would be unexpected, as seems to faults are included in the extension rate cal- be the case for at least the Tabernacle fault. Active culations. Note that uncertainties in GPS velocities (Table 3) are 1σ and those in fault extension rates are 2σ. detachment faulting underlying a thin, hot upper plate may lead to a similar surface expression of faulting as observed in the eastern Sevier Desert we considered, it is possible that off-fault, intraba- near-vertical zones of low resistivity in the upper (Jänecke and Evans, 2017), but it is difficult to rec- sin deformation in the Tule Valley (House Range) crust, from the surface to >6 km depth, beneath oncile the variability in eastern Sevier Desert fault and Sevier Lake (Cricket Mountains) (Fig. 1) is not the Clear Lake, Tabernacle, and Pavant faults (Wan- extension rates with them being hanging-wall preserved as well as on volcanic edifices in the namaker et al., 2013; Liu and Hasterok, 2016), (2) splays of a common detachment at depth. Fur- eastern domain, and therefore could account for at regionally high heat flow and geothermal gradients thermore, neither modern strain observed in GPS least some of the rate discrepancy. However, the (Hardwick and Chapman, 2012; Gwynn et al., 2013), nor fault displacements are adequately fit by creep slip rates we report are similar to rates and recur- and (3) locally thin (~25 km) lithospheric mantle or interseismic strain accumulation on an active rence intervals observed on other range-bounding and prominent low-velocity zones in the sublitho- Sevier Desert detachment (Stahl and Niemi, 2017). (or intrabasin) normal faults in the interior of the spheric mantle (York and Helmberger, 1973; Nelson Basin and Range (Pérouse and Wernicke, 2017; Per- and Tingey, 1997; Schmandt and Lin 2014; Valen- sonius et al., 2017), and we therefore consider that tine et al., 2017), we propose a revised neotectonic Western Domain off-fault deformation cannot account for the large model for the eastern Sevier Desert that builds on disparities we observe over the same time scales. the framework of Wannamaker et al. (2008) (Fig. 12). Range-bounding faults of the western domain Collectively, these observations lead to the interpre- In this model, far-field tectonic strain is accommo- (Cricket Mountains and House Range) are charac- tation of western-domain faults as being tectonic dated in the eastern Sevier Desert by thinning of the terized by simple, continuous fault traces at the faults that extend through the seismogenic crust lithospheric mantle (e.g., Wannamaker et al., 2008) surface. These faults displace Late Pleistocene (e.g., Allmendinger et al., 1983; Greene, 2014), and and, depending on magma supply, eventually cul- to Holocene alluvial fans with SEDs of ~1 m over therefore accumulate and release elastic strain over minates in episodic dike intrusion and associated narrow zones (~10 m) of deformation, but have the course of a seismic cycle. faulting in the upper crust. This differs from previ- accumulated significant topographic relief (hun- ously proposed modes of late Quaternary faulting, dreds of meters) since the late Cenozoic (ca. 15–20 which include salt tectonics (Wills et al., 2005) and Ma; Stockli et al., 2001). The Cricket Mountains and Magma-Assisted Rifting in the Eastern Domain underlying detachment faulting on the Sevier Des- House Range faults exhibit slower extension rates ert detachment (e.g., Niemi et al., 2004). than the eastern domain faults (Fig. 11). While it is Integrating our observations with regional This model indicates episodes of transient, ele- likely that preservation is not an issue at the sites geophysical data, including (1) the presence of vated strain rates during dike-fed volcanism, and

1 can explain the elevated paleoseismic extension 113°W 12°W rates on the Clear Lake and Tabernacle faults, as House Range ? ? Eastern domain: compared to modern GPS rates (Fig. 11). There are Magma-assisted examples of this process occurring elsewhere in 39°N Western domain: extension the Basin and Range. Mackey et al. (2014) found Tectonic faulting SDD WFZ

t l evidence for synchronous dike-fed volcanism and Sevier e B

faulting at ca. 14 ka in the Fort Rock Basin of Oregon, N Lake ic sm ei S with minimal or no activity since. In 2003, a dike n ai nt injection event beneath Lake Tahoe resulted in a ou rm te n local strain transient, as implied by GPS veloci- Magmatic ﬂuids and melt I Abandoned SDD channeled along faults ties, of at least an order of magnitude greater than Crust Decompression melting observed over the previous seven years (Smith EQ Hypocenters feeding dike intrusion et al., 2004). Had the resulting extension been Lithospheric Mantle resolved on faults at the surface, apparent exten- Low-velocity zone underlying eastern sion rates across those structures would far exceed Asthenosphere Sevier Desert modern GPS or longer-term geologic rates, similar to the temporal relationships that we observe on Figure 12. Schematic model of active faulting across the eastern margin of the Basin and Range in the Sevier Desert and the Clear Lake and Tabernacle faults (Fig. 11). adjacent regions. Large white arrows show the regional extension direction. We propose that thinned lithospheric mantle and crust evident in P-wave tomography (Wannamaker et al., 2008; Schmandt and Lin, 2014; Valentine et al., 2017) formed This revised model for the eastern Sever basin in large part due to rapid Oligocene–Miocene slip on the Sevier Desert detachment (SDD) (e.g., Stockli et al., 2001; Wills requires that strain is currently partitioned into et al., 2005; Stahl and Niemi, 2017). This has facilitated passive upwelling of the asthenosphere and decompression melt- magma-assisted and tectonic-dominated segments ing localized in the eastern Sevier Desert and Black Rock Desert volcanic field (e.g., Nelson and Tingey, 1997; Ebinger and Casey, 2001; Wannamaker et al., 2008; Valentine et al., 2017). Modern extension in the lower crust and mantle lithosphere across the Sevier Desert, akin to the segmentation likely takes place via distributed shear, and in the upper crust primarily by fault slip related to dike injection and shallow observed within and across segments of narrow magmatism. Thus, high fault extension rates here over 103–104 yr time scales reflect irregular magma supply rates to the rifts (e.g., Ebinger, 2005; Rowland et al., 2010) upper crust in response to steady far-field tectonic extension. WFZ—Wasatch fault zone. (Fig. 12). However, our model also has intriguing consequences for along-strike variations in strain accommodation along the eastern margin of the sub-basins within the Basin and Range (e.g., Athens transition in strain accommodation are beyond the Basin and Range. One implication of our model is that et al., 2016), and our results may imply that dike- scope of this study, we consider it most likely that the eastern domain of the Sevier Desert also marks driven extension is more relevant than previously the Sevier Desert detachment accommodated rel- an along-strike transition in strain accommodation, recognized. The wealth of geophysical data available atively rapid extension in the Oligocene–Miocene from solely tectonic faulting along the Wasatch fault within the Sevier Desert region, along with ease of (Stockli et al., 2001), and Plio-Pleistocene volca- to the north, to the observed <1 mm yr−1 component access and exposure, may thus provide a natural nism and associated faulting represents a late to of localized magma-assisted rifting in the eastern laboratory to investigate spatially complex segmen- post-extensional phase of basaltic volcanism com- Sevier Desert to the south (with most of the total ~4 tation that can be used to understand the varying mon throughout the Basin and Range (Gans and mm yr−1 still being accommodated on or near the modes of continental extension elsewhere. Bohrson, 1998). Wasatch fault). Such variability in modes of strain Our model for strain accommodation in the accommodation is perhaps not surprising given Sevier Desert region (Fig. 12) is consistent with geo- that both modes of extension and surface faulting detic and paleoseismic observations and applies ■■ CONCLUSIONS are observed along the western Basin and Range over the duration of pervasive volcanic activity in margin (Bursik and Sieh, 1989; Smith et al., 2004), the Black Rock volcanic field (minimum 2.5 m.y.; Using new mapping, geochronology, and survey between western and eastern branches of the East Johnsen et al., 2010). Prior to the Pleistocene, strain data, we present a revised model of late Quater- African Rift, along the eastern branch of the East accommodation in the Sevier Desert was likely nary tectono-magmatic activity in the Sevier Desert African Rift (Hayward and Ebinger, 1996; Muirhead accommodated via slip on the Sevier Desert detach- of Utah. High-resolution topography and Quater- et al., 2015, 2016), and in the Taupo Volcanic Zone of ment (Fig. 12), for which there is sound geologic nary geochronology helped to constrain the styles, New Zealand (Rowland et al., 2010). However, such evidence (e.g., Stockli et al., 2001; DeCelles and rates, and timing of surface faulting. The results variability in strain accommodation mechanisms has Coogan, 2006). Although consideration of this ear- demonstrate that faults at the eastern margin of only recently been proposed for slowly extending lier phase of faulting and the reasons for a temporal the Basin and Range in central Utah comprise two

distinct fault domains. Time-integrated extension Great Basin, Nevada, Utah, and California: Geological Soci- Crone, A.J., and Harding, S.T., 1984, Relationship of late Qua- ety of America Bulletin, v. 105, p. 56–76, https://doi .org/10 ternary fault scarps to subjacent faults, eastern Great Basin, rates increase from west to east across the Sevier .1130/0016-7606(1993)105<0056:STPATC>2.3.CO;2. Utah: Geology, v. 12, p. 292–295, https://doi .org /10 .1130 /0091 Desert, and extension rates across Late Pleistocene Balco, G., Stone, J.O., Lifton, N.A., and Dunai, T.J., 2008, A com- -7613(1984)12<292:ROLQFS>2.0.CO;2. and Holocene markers in the eastern Sevier Des- plete and easily accessible means of calculating surface Currey, D.R., 1982, Lake Bonneville: Selected features of rel- exposure ages or erosion rates from 10Be and 26Al measure- evance to neotectonic analysis: U.S. Geological Survey ert are an order of magnitude higher than modern ments: Quaternary Geochronology, v. 3, p. 174–195, https:// Open-File Report 82-1070, 30 p. GPS-derived extension rates, which we attribute to doi.org/10.1016/j.quageo.2007.12.001. Currey, D.R., 1990, Quaternary palaeolakes in the evolution of punctuated strain release during dike-fed volcanism. Bennett, R.A., Wernicke, B.P., Niemi, N.A., Friedrich, A.M., and semidesert basins, with special emphasis on Lake Bonneville Davis, J.L., 2003, Contemporary strain rates in the northern The revised model of active tectonics presented and the Great Basin, U.S.: Palaeogeography, Palaeoclimatol- Basin and Range province from GPS data: Tectonics, v. 22, ogy, Palaeoecology, v. 76, p. 189–214, https://doi .org /10 .1016 here points toward across-strike segmentation of https://doi.org/10.1029/2001TC001355. /0031-0182 (90)90113 -L. the eastern Basin and Range into magma-assisted Best, M.G., McKee, E.H., and Damon, P.E., 1980, Space-time- DeCelles, P.G., and Coogan, J.C., 2006, Regional structure and composition patterns of late Cenozoic mafic volcanism, and tectonic segments, making the Sevier Desert kinematics history of the Sevier fold-and-thrust belt, cen- southwestern Utah and adjoining areas: American Jour- tral Utah: Geological Society of America Bulletin, v. 118, an important locale for understanding spatial and nal of Science, v. 280, p. 1035–1050, https://doi .org/10.2475 p. 841–864, https://doi.org/10.1130/B25759.1. temporal controls on rift segmentation. /ajs.280.10.1035. Dolan, J.F., and Haravitch, B.D., 2014, How well do surface Bilham, R., Bendick, R., Larson, K., Mohr, P., Braun, J., Tesfaye, slip measurements track slip at depth in large strike-slip S., and Asfaw, L., 1999, Secular and tidal strain across the earthquakes? The importance of fault structural maturity in Main Ethiopian Rift: Geophysical Research Letters, v. 26, controlling on-fault slip versus off-fault surface deformation: ACKNOWLEDGMENTS p. 2789–2792, https://doi.org/10.1029/1998GL005315. Earth and Planetary Science Letters, v. 388, p. 38–47, https:// This work was supported by U.S. National Science Foundation Brun, J.-P., 1999, Narrow rifts versus wide rifts: Inferences for doi.org/10.1016/j.epsl.2013.11.043. (NSF) grants EAR 1451466 to Stahl and CAREER 1151247 to Niemi. the mechanics of rifting from laboratory experiments: Phil- Ebinger, C., 2005, Continental break-up: The East African per- 10Be dating was funded by a Purdue Rare Isotope Measurement osophical Transactions of the Royal Society of London A: spective: Astronomy & Geophysics, v. 46, p. 2.16–2.21, Mathematical, Physical and Engineering Sciences, v. 357, (PRIME) Lab (Purdue University, West Lafayette, Indiana, USA) https://doi.org/10.1111/j.1468-4004.2005.46216.x. p. 695–712, https://doi.org/10.1098/rsta.1999.0349. Seed grant to Niemi and Stahl. Amanda Maslyn assisted with Ebinger, C.J., and Casey, M., 2001, Continental breakup in mag- Buck, W.R., 1991, Modes of continental lithospheric extension: quartz and olivine mineral separation. We thank Matt Heizler at matic provinces: An Ethiopian example: Geology, v. 29, Journal of Geophysical Research, v. 96, p. 20,161–20,178, New Mexico Geochronology Research Laboratory (Socorro, New p. 527–530, https://doi .org /10 .1130 /0091 -7613 (2001)029 <0527: https://doi.org/10.1029/91JB01485. Mexico, USA), Mark Kurz and Josh Curtice at Woods Hole Ocean- CBIMPA>2.0 .CO;2. Bunds, M., Andreini, J., Wells, J.D., and Stahl, T.A., 2019, High ographic Institution (Woods Hole, Massachusetts, USA), and Ertec Western Inc., 1981, MX siting investigation, faults and linea- Resolution Topography of a Portion of the House Range Tom Woodruff and Tom Clifton at PRIME Lab for their help and ments in the MX siting region, Nevada and Utah: Long Beach, Fault and Pleistocene Lake Bonneville Shorelines, Sevier support. We would like to thank the Utah Geological Survey (Salt California, unpublished consultant’s report no. E‑TR‑54 for Desert, Utah, USA: Distributed by OpenTopography, https// Lake City, Utah), including Steve Bowman, Adam Hiscock, Gregg U.S. Air Force, volume I, 77 p.; volume II, variously paginated. doi.org /10.5069 /G9348HH6. Beukelman, Greg McDonald, and Ben Erickson, for field assis- Ferrill, D.A., Morris, A.P., McGinnis, R.N., Smart, K.J., Wat- Bursik, M., and Sieh, K., 1989, Range front faulting and vol- tance and discussion. Thorough reviews by Craig McGee, Gary son-Morris, M.J., and Wigginton, S.S., 2016, Observations canism in the Mono Basin, eastern California: Journal of Axen, and two anonymous reviewers significantly improved this on normal-fault scarp morphology and fault system evo- Geophysical Research, v. 94, p. 15,587–15,609, https://doi manuscript. John Sandru and Chris Crosby at UNAVCO (Boulder, lution of the Bishop Tuff in the Volcanic Tableland, Owens .org/10.1029/JB094iB11p15587. Colorado) are thanked for their generous support, for assistance Valley, California, U.S.A.: Lithosphere, v. 8, p. 238–253, Calais, E., d’Oreye, N., Albaric, J., Deschamps, A., Delvaux, D., in processing TLS data, and for access to Trimble Business Center Déverchère, J., Ebinger, C., Ferdinand, R.W., Kervyn, F., https://doi.org/10.1130/L476.1. software for processing survey data. Macheyeki, A.S., Oyen, A., Perrot, J., Saria, E., Smets, B., Friedrich, A.M., Wernicke, B.P., Niemi, N.A., Bennett, R.A., and Stamps, D.S., and Wauthier, C., 2008, Strain accommoda- Davis, J.L., 2003, Comparison of geodetic and geologic data tion by slow slip and dyking in a youthful continental rift, from the Wasatch region, Utah, and implications for the spectral character of Earth deformation at periods of 10 to REFERENCES CITED East Africa: Nature, v. 456, p. 783–787, https://doi.org /10 .1038 /nature07478. 10 million years: Journal of Geophysical Research, v. 108, Acocella, V., and Trippanera, D., 2016, How diking affects the Case, R.W., and Cook, K.L., 1979, A gravity survey of the Sevier 2199, https://doi.org/10.1029/2001JB000682. tectonomagmatic evolution of slow spreading plate bound- Lake area, Millard County, Utah: Utah Geology, v. 6, p. 55–76. Gans, P.B., and Bohrson, W.A., 1998, Suppression of volcanism aries: Overview and model: Geosphere, v. 12, p. 867–883, Cerling, T.E., 1990, Dating geomorphologic surfaces using cos- during rapid extension in the Basin and Range province, https://doi.org/10.1130/GES01271.1. mogenic 3He: Quaternary Research, v. 33, p. 148–156, https:// United States: Science, v. 279, p. 66–68, https://doi.org/10 Allmendinger, R.W., Sharp, J.W., Von Tish, D., Serpa, L., Brown, doi.org/10.1016/0033-5894(90)90015-D. .1126/science.279.5347.66. L., Kaufman, S., Oliver, J., and Smith, R.B., 1983, Cenozoic Condie, K.C., and Barsky, C.K., 1972, Origin of Quaternary basalts Godsey, H.S., Oviatt, C.G., Miller, D.M., and Chan, M.A., 2011, and Mesozoic structure of the eastern Basin and Range prov- from the Black Rock Desert region, Utah: Geological Society Stratigraphy and chronology of offshore to nearshore ince, Utah, from COCORP seismic-reflection data: Geology, of America Bulletin, v. 83, p. 333–352, https://doi .org /10 .1130 deposits associated with the Provo shoreline, Pleistocene v. 11, p. 532–536, https://doi.org/10.1130/0091-7613(1983)11 /0016-7606(1972)83[333:OOQBFT]2.0.CO;2. Lake Bonneville, Utah: Palaeogeography, Palaeoclimatology, <532:CAMSOT>2.0.CO;2. Corti, G., van Wijk, J., Cloetingh, S., and Morley, C.K., 2007, Tec- Palaeoecology, v. 310, p. 442–450, https://doi.org/10.1016/j Athens, N.D., Glen, J.M.G., Klemperer, S.L., Egger, A.E., and Fon- tonic inheritance and continental rift architecture: Numerical .palaeo.2011.08.005. tiveros, V.C., 2016, Hidden intrabasin extension: Evidence for and analogue models of the East African Rift system: Tec- Gómez-Vasconcelos, M.G., Villamor, P., Cronin, S., Procter, J., dike-fault interaction from magnetic, gravity, and seismic tonics, v. 26, TC6006, https://doi .org /10 .1029 /2006TC002086. Palmer, A., Townsend, D., and Leonard, G., 2017, Crustal reflection data in Surprise Valley, northeastern California: Cowie, P.A., Scholz, C.H., Edwards, M., and Malinverno, A., 1993, extension in the Tongariro graben, New Zealand: Insights Geosphere, v. 12, p. 15–25, https://doi .org /10 .1130 /GES01173 .1. Fault strain and seismic coupling on mid-ocean ridges: Jour- into volcano-tectonic interactions and active deformation in Axen, G.J., Taylor, W.J., and Bartley, J.M., 1993, Space-time pat- nal of Geophysical Research, v. 98, p. 17,911–17,920, https:// a young continental rift: Geological Society of America Bul- terns of the onset of extension and magmatism, southern doi.org/10.1029/93JB01567. letin, v. 129, p. 1085–1099, https://doi.org/10.1130/B31657.1.

Greene, D.C., 2014, The Confusion Range, west-central Utah: low stand of Great Salt Lake, in Lund, W.R., Emerman, S.H., Letters, v. 351–352, p. 182–194, https://doi .org /10 .1016 /j .epsl Fold-thrust deformation and a western Utah thrust belt in Wang, W., and Zanazzi, A., eds., Geology and Resources of .2012.07.019. the Sevier hinterland: Geosphere, v. 10, p. 148–169, https:// the Wasatch: Back to Front: Utah Geological Association McQuarrie, N., and Oskin, M., 2010, Palinspastic restoration of doi.org/10.1130/GES00972.1. Publication 46, p. 295–360. NAVDat and implications for the origin of magmatism in south- Guerrero, J., Bruhn, R. L., McCalpin, J.P., Gutiérrez, F., Willis, G., Janecke, S.U., and Oaks, R.Q., Jr. 2011, New insights into the western North America: Journal of Geophysical Research, and Mozafari, M., 2015, Salt-dissolution faults versus tec- outlet conditions of late Pleistocene Lake Bonneville, south- v. 115, B10401, https://doi .org /10 .1029 /2009JB006435. tonic faults from the case study of salt collapse in Spanish eastern Idaho, USA: Geosphere, v. 7, p. 1369–1391, https:// McQuarrie, N., and Wernicke, B.P., 2005, An animated tec- Valley, SE Utah (USA): Lithosphere, v. 7, p. 46–58, https:// doi.org/10.1130/GES00587.1. tonic reconstruction of southwestern North America since doi.org/10.1130/L385.1. Johnsen, R.L., Smith, E.I., and Biek, R.F., 2010, Subalkaline vol- 36 Ma: Geosphere, v. 1, p. 147–172, https://doi .org/10.1130 Gwynn, M., Blackett, B., Allis, R., and Hardwick, C., 2013, New canism in the Black Rock Desert and Markagunt Plateau /GES00016.1. geothermal resource delineated beneath Black Rock Desert, volcanic fields of south-central Utah,in Carney, S.M., Tabet, Medynski, S., Pik, R., Burnard, P., Dumont, S., Grandin, R., Williams, Utah: Proceedings of the 38th Workshop on Geothermal D.W., and Johnson, C.L., eds., Geology of South-Central A., Blard, P. H., Schimmelpfennig, I., Vye-Brown, C., France, Reservoir Engineering, Feb 11–13, Stanford, CA, p. 1511–1519. Utah: Utah Geological Association Publication 39, p. 109–150. L., Ayalew, D., Benedetti, L., and Yirgu, G., 2016, Magmatic Hammond, W.C., and Thatcher, W., 2004, Contemporary tec- Keir, D., Ebinger, C.J., Stuart, G.W., Daly, E., and Ayele, A., 2006, cycles pace tectonic and morphological expression of rifting tonic deformation of the Basin and Range province, western Strain accommodation by magmatism and faulting as rifting (Afar depression, Ethiopia): Earth and Planetary Science Let- United States: 10 years of observation with the Global Posi- proceeds to breakup: Seismicity of the northern Ethiopian ters, v. 446, p. 77–88, https://doi .org /10 .1016 /j .epsl .2016 .04 .014. tioning System: Journal of Geophysical Research, v. 109, rift: Journal of Geophysical Research, v. 111, B05314, https:// Miller, D.M., 2016, The Provo shoreline of Lake Bonneville, in B08403, https://doi.org/10.1029/2003JB002746. doi.org/10.1029/2005JB003748. Oviatt, C.G., and Shroder, J.F., eds., Lake Bonneville: A Sci- Hardwick, C., and Chapman, D.S., 2012, Geothermal resources in Levander, A., and Miller, M.S., 2012, Evolutionary aspects of entific Update: Elsevier, Developments in Earth Surface the Black Rock Desert, Utah: MT and gravity surveys: Geo- lithosphere discontinuity structure in the western US: Geo- Processes, v. 20, p. 127–144, https://doi.org/10.1016/B978 thermal Resource Council Transactions, v. 36, p. 903–906. chemistry Geophysics Geosystems, v. 13, Q0AK07, https:// -0-444-63590-7.00007-X. Hayward, N.J., and Ebinger, C.J., 1996, Variations in the along- doi.org/10.1029/2012GC004056. Miller, D.M., Oviatt, C.G., and McGeehin, J.P., 2013, Stratigraphy axis segmentation of the Afar Rift system: Tectonics, v. 15, Lifton, N., Caffee, M., Finkel, R., Marrero, S., Nishiizumi, K., and chronology of Provo shoreline deposits and lake-level p. 244-257, https://doi.org/10.1029/95TC02292. Phillips, F.M., Goehring, B., Gosse, J., Stone, J., Schaefer, implications, Late Pleistocene Lake Bonneville, eastern Hecker, S., 1993, Quaternary tectonics of Utah with emphasis J., Theriault, B., Jull, A.J.T., and Fifield, K., 2015, In situ Great Basin, USA: Boreas, v. 42, p. 342–361, https://doi .org on earthquake-hazard characterization: Utah Geological cosmogenic nuclide production rate calibration for the /10.1111/j.1502-3885.2012.00297.x. Survey Bulletin 127, 157 p., 2 plates. CRONUS-Earth project from Lake Bonneville, Utah, shore- Muirhead, J.D., Kattenhorn, S.A., and Le Corvec, N., 2015, Vary- Hintze, L.F., and Davis, F.D., 2002a, Geologic map of the Delta line features: Quaternary Geochronology, v. 26, p. 56–69, ing styles of magmatic strain accommodation across the 30′ x 60′ quadrangle and part of the Lynndyl 30′ x 60′ quad- https://doi.org/10.1016/j.quageo.2014.11.002. East African Rift: Geochemistry Geophysics Geosystems, rangle, northeast Millard County and parts of Juab, Sanpete, Lindsey, D.A., Glanzman, R.K., Naeser, C.W., and Nichols, D.J., v. 16, p. 2775–2795, https://doi.org/10.1002/2015GC005918. and Sevier Counties, Utah: Utah Geological Survey Map 184, 1981, Upper Oligocene evaporites in basin fill of Sevier Muirhead, J.D., Kattenhorn, S.A., Lee, H., Mana, S., Turrin, B.D., scale 1:100,000. Desert region, western Utah: American Association of Fischer, T.P., Kianji, G., Dindi, E., and Stamps, D.S., 2016, Hintze, L.F., and Davis, F.D., 2002b, Geologic map of the Wah Petroleum Geologists Bulletin, v. 65, p. 251–260, https:// Evolution of upper crustal faulting assisted by magmatic Wah Mountains North 30′ x 60′ quadrangle and part of the doi.org/10.1306/2F9197B5-16CE-11D7-8645000102C1865D. volatile release during early-stage continental rift develop- Garrison 30′ x 60′ quadrangle, southwest Millard County Liu, L., and Hasterok, D., 2016, High-resolution lithosphere vis- ment in the East African Rift: Geosphere, v. 12, p. 1670–1700, and part of Beaver County, Utah: Utah Geological Survey cosity and dynamics revealed by magnetotelluric imaging: https://doi.org/10.1130/GES01375.1. Map 182, scale 1:100,000. Science, v. 353, p. 1515–1519, https://doi .org /10 .1126 /science Nelson, S.T., and Tingey, D.G., 1997, Time-transgressive and Hintze, L.F., and Davis, F.D., 2003, Geology of Millard County, .aaf6542. extension-related basaltic volcanism in southwest Utah Utah: Utah Geological Survey Bulletin 133, 303 p. Long, S.P., 2018, Geometry and magnitude of extension in the and vicinity: Geological Society of America Bulletin, v. 109, Hintze, L.F., Davis, F.D., Rowley, P.D., Cunningham, C.G., Steven, Basin and Range Province (39°N), Utah, Nevada, and Califor- p. 1249–1265, https://doi.org/10.1130/0016-7606(1997)109 T.A., and Willis, G.C., 2003, Geologic map of the Richfield nia, USA: Constraints from a province-scale cross section: <1249:TTAERB>2.3.CO;2. 30′ x 60′ quadrangle, southeast Millard County and parts of Geological Society of America Bulletin, v. 131, p. 99–119, Nestola, Y., Storti, F., and Cavozzi, C., 2015, Strain rate-depen- Beaver, Piute, and Sevier Counties, Utah: Utah Geological https://doi.org/10.1130/B31974.1. dent lithosphere rifting and necking architectures in analog Survey Map 195, scale 1:100,000. Mackey, B.H., Castonguay, S.R., Wallace, P.J., and Weldon, R.J., experiments: Journal of Geophysical Research: Solid Earth, Hollingsworth, J., Leprince, S., Ayoub, F., and Avouac, J.-P., 2013, 2014, Synchronous late Pleistocene extensional faulting v. 120, p. 584–594, https://doi.org/10.1002/2014JB011623. New constraints on dike injection and fault slip during the and basaltic volcanism at Four Craters Lava Field, central Niemi, N.A., Wernicke, B.P., Friedrich, A.M., Simons, M., Bennett, 1975–1984 Krafla rift crisis, NE Iceland: Journal of Geophys- Oregon, USA: Geosphere, v. 10, p. 1247–1254, https://doi R.A., and Davis, J.L., 2004, BARGEN continuous GPS data ical Research: Solid Earth, v. 118, p. 3707–3727, https://doi .org/10.1130/GES00990.1. across the eastern Basin and Range province, and impli- .org/10.1002/jgrb.50223. Mastin, L.G., and Pollard, D.D., 1988, Surface deformation and cations for fault system dynamics: Geophysical Journal Hoover, J.D., 1974, Periodic Quaternary volcanism in the Black shallow dike intrusion processes at Inyo Craters, Long International, v. 159, p. 842–862, https://doi .org /10 .1111 /j .1365 Rock Desert, Utah: Brigham Young University Geology Stud- Valley, California: Journal of Geophysical Research, v. 93, -246X.2004.02454.x. ies, v. 21, no. 1, p. 3–73. p. 13,221–13,235, https://doi.org/10.1029/JB093iB11p13221. O’Connor, J.E., 1993, Hydrology, Hydraulics, and Geomorphol- Ibs-von Seht, M., Blumenstein, S., Wagner, R., Hollnack, D., McBride, J.H., Nelson, S.T., Heiner, B.D., Tingey, D.G., Morris, ogy of the Bonneville Flood: Geological Society of America and Wohlenberg, J., 2001, Seismicity, seismotectonics and T.H., and Rey, K.A., 2015, Neotectonics of the Sevier Desert Special Paper 274, 80 p., https://doi.org/10.1130/SPE274. crustal structure of the southern Kenya Rift—New data from basin, Utah as seen through the lens of multi-scale geo- Oskin, M.E., and Prush, V.B., 2016, Modeling clast lifetimes: A the Lake Magadi area: Geophysical Journal International, physical investigations: Tectonophysics, v. 654, p. 131–155, new approach to cosmogenic dating of alluvial fan surfaces: v. 146, p. 439–453, https://doi.org/10.1046/j.0956-540x.2001 https://doi.org/10.1016/j.tecto.2015.05.007. Southern California Earthquake Center Project 15209 Report, .01464.x. McGee, D., Quade, J., Edwards, R.L., Broecker, W.S., Cheng, H., 6 p., https://www.scec.org/proposal/report/15209. Jänecke, S.U., and Evans, J.P., 2017, Revised structure and cor- Reiners, P.W., and Evenson, N., 2012, Lacustrine cave car- Oviatt, C.G., 1989, Quaternary geology of part of the Sevier relation of the East Great Salt Lake, North Promontory, Rozel bonates: Novel archives of paleohydrologic change in the Desert, Millard County, Utah: Utah Geological and Mineral and Hansel Valley fault zones revealed by the 2015–2016 Bonneville Basin (Utah, USA): Earth and Planetary Science Survey Special Study 70, 46 p.

Oviatt, C.G., 1991, Quaternary geology of the Black Rock Des- Rubin, A.M., and Pollard, D.D., 1988, Dike-induced faulting in Villamor, P., Van Dissen, R., Alloway, B.V., Palmer, A.S., and ert, Millard County, Utah: Utah Geological Survey Special rift zones: Geology, v. 16, p. 413–417, https://doi .org/10 .1130 Litchfield, N., 2007, The Rangipo fault, Taupo rift, New Zea- Study 73, 27 p. /0091-7613(1988)016<0413:DIFIRZ>2.3.CO;2. land: An example of temporal slip-rate and single-event Oviatt, C.G., 2015, Chronology of Lake Bonneville, 30,000 to Sack, D., 1990, Quaternary geology of Tule Valley, west-central displacement variability in a volcanic environment: Geolog- 10,000 yr B.P.: Quaternary Science Reviews, v. 110, p. 166– Utah: Utah Geological and Mineral Survey Map 124, scale ical Society of America Bulletin, v. 119, p. 529–547, https:// 171, https://doi.org/10.1016/j.quascirev.2014.12.016. 1:100,000. doi.org/10.1130/B26000.1. Oviatt, C.G., and Nash, W.P., 1989, Late Pleistocene basaltic ash Schantz, K.A., 2016, The use of multiple dating methods to deter- Villamor, P., Berryman, K.R., Nairn, I.A., Wilson, K., Litchfield, and volcanic eruptions in the Bonneville basin, Utah: Geo- mine the age of basalt in the Ice Springs Volcanic Field, N., and Ries, W., 2011, Associations between volcanic erup- logical Society of America Bulletin, v. 101, p. 292–303, https:// Millard County, Utah [senior independent study thesis]: tions from Okataina volcanic center and surface rupture doi.org /10 .1130 /0016 -7606 (1989)101 <0292: LPBAAV>2 .3 .CO;2. Wooster, Ohio, College of Wooster, Paper 7234. of nearby active faults, Taupo rift, New Zealand: Insights Oviatt, C.G., and Shroder, J.F., eds., 2016, Lake Bonneville: A Schmandt, B., and Lin, F.-C., 2014, P and S wave tomography of the into the nature of volcano-tectonic interactions: Geological Scientific Update: Amsterdam, Elsevier, Developments in mantle beneath the United States: Geophysical Research Let- Society of America Bulletin, v. 123, p. 1383–1405, https://doi Earth Surface Processes, v. 20, 659 p. ters, v. 41, p. 6342–6349, https://doi .org /10.1002 /2014GL061231. .org/10.1130/B30184.1. Owen, L.A., Frankel, K.L., Knott, J.R., Reynhout, S., Finkel, R.C., Scholz, C.H., and Contreras, J.C., 1998, Mechanics of continental Wannamaker, P.E., Hasterok, D.P., Johnston, J.M., Stodt, J.A., Dolan, J.F., and Lee, J., 2011, Beryllium-10 terrestrial cos- rift architecture: Geology, v. 26, p. 967–970, https://doi .org /10 Hall, D.B., Sodergren, T.L., Pellerin, L., Maris, V., Doerner, mogenic nuclide surface exposure dating of Quaternary .1130/0091-7613(1998)026<0967:MOCRA>2.3.CO;2. W.M., Groenewold, K.A., and Unsworth, M.J., 2008, Litho- landforms in Death Valley: Geomorphology, v. 125, p. 541– Smith, K.D., von Seggern, D., Blewitt, G., Preston, L., Anderson, J.G., spheric dismemberment and magmatic processes of the 557, https://doi.org/10.1016/j.geomorph.2010.10.024. Wernicke, B.P., and Davis, J.L., 2004, Evidence for deep magma Great Basin–Colorado Plateau transition, Utah, implied from Parsons, T., and Thompson, G.A., 1991, The role of magma injection beneath Lake Tahoe, Nevada-California: Science, magnetotellurics: Geochemistry Geophysics Geosystems, overpressure in suppressing earthquakes and topography: v. 305, p. 1277–1280, https://doi.org/10.1126/science.1101304. v. 9, Q05019, https://doi.org/10.1029/2007GC001886. Worldwide examples: Science, v. 253, p. 1399–1402, https:// Smith, R.P., Jackson, S.M., and Hackett, W.R., 1996, Paleoseis- Wannamaker, P.E., Maris, V., and Hardwick, C.L., 2013, Basin doi.org/10.1126/science.253.5026.1399. mology and seismic hazards evaluations in extensional and rift structure of the central Black Rock Desert, Utah, Patzkowsky, S., Randall, E., Rosen, M.L., Thompson, A., Moua, volcanic terrains: Journal of Geophysical Research, v. 101, and initial thermal implications, from 3D magnetotellurics: P.N., Schantz, K., Pollock, M., Judge, S.A., Williams, M., and p. 6277–6292, https://doi.org/10.1029/95JB01393. Geothermal Resource Council Transactions, v. 37, p. 41–44. Matesich, C., 2017, New cosmogenic and VML dates and Stahl, T., and Niemi, N.A., 2017, Late Quaternary faulting in the Wells, D.L., and Coppersmith, K.J., 1994, New empirical rela- revised emplacement history of the Ice Springs Volcanic Sevier Desert driven by magmatism: Scientific Reports, v. 7, tionships among magnitude, rupture length, rupture width, Field in the Black Rock Desert, Utah: Geological Society of 44372 , https://doi.org/10.1038/srep44372. rupture area, and surface displacement: Bulletin of the Seis- America Abstracts with Programs, v. 49, no. 6, https://doi Stockli, D.F., Linn, J.K., Walker, J.D., and Dumitru, T.A., 2001, Mio- mological Society of America, v. 84, p. 974–1002. .org/10.1130/abs/2017AM-306786. cene unroofing of the Canyon Range during extension along Wesnousky, S.G., 2008, Displacement and geometrical char- Payne, S.J., Hackett, W.R., and Smith, R.P., 2009, Paleoseismology the Sevier Desert Detachment, west central Utah: Tecton- acteristics of earthquake surface ruptures: Issues and of volcanic environments, in McCalpin, J.P., ed., Paleoseis- ics, v. 20, p. 289–307, https://doi.org/10.1029/2000TC001237. implications for seismic-hazard analysis and the process mology: International Geophysics, v. 95: Amsterdam, Elsevier, Stuiver, M., Reimer, P.J., and Reimer, R.W., 2019, CALIB 7.1 [WWW of earthquake rupture: Bulletin of the Seismological Soci- p. 271–314, https://doi .org /10 .1016 /S0074 -6142 (09) 95004 -5. program] at http://calib.org (accessed 31 October 2019). ety of America, v. 98, p. 1609–1632, https://doi .org/10.1785 Pérouse, E., and Wernicke, B.P., 2017, Spatiotemporal evolu- Thompson, R.S., Oviatt, C.G., Honke, J.S., and McGeehin, J.P., /0120070111. tion of fault slip rates in deforming continents: The case 2016, Late Quaternary changes in lakes, vegetation, and WGUEP (Working Group on Utah Earthquake Probabilities), 2016, of the Great Basin region, northern Basin and Range prov- climate in the Bonneville basin reconstructed from sediment Earthquake probabilities for the Wasatch Front region in ince: Geosphere, v. 13, p. 112–135, https://doi.org/10.1130 cores from Great Salt Lake, in Oviatt, C.G., and Shroder, J.F., Utah, Idaho, and Wyoming: Utah Geological Survey Mis- /GES01295.1. eds., Lake Bonneville: A Scientific Update: Elsevier, Develop- cellaneous Publication 16-3, 164 p., 5 appendices. Personius, S.F., Briggs, R.W., Maharrey, J.Z., Angster, S.J., and ments in Earth Surface Processes, v. 20, p. 221–291, https:// Wills, S., Anders, M.H., and Christie-Blick, N., 2005, Pattern Mahan, S.A., 2017, A Paleoseismic transect across the north- doi.org/10.1016/B978-0-444-63590-7.00011-1. of Mesozoic thrust surfaces and Tertiary normal faults in western Basin and Range Province, northwestern Nevada Thompson, S.C., Weldon, R.J., Rubin, C.M., Abdrakhmatov, K., the Sevier Desert subsurface, west-central Utah: Ameri- and northeastern California, USA: Geosphere, v. 13, p. 782– Molnar, P., and Berger, G.W., 2002, Late Quaternary slip can Journal of Science, v. 305, p. 42–100, https://doi .org 810, https://doi.org/10.1130/GES01380.1. rates across the central Tien Shan, Kyrgyzstan, central Asia: /10.2475/ajs.305.1.42. Piekarski, L.L., 1980, Relative age determination of Quaternary Journal of Geophysical Research, v. 107, 2203, https://doi .org Wright, T.J., Ebinger, C., Biggs, J., Ayele, A., Yirgu, G., Keir, D., fault scarps along the southern Wasatch, Fish Springs, and /10.1029/2001JB000596. and Stork, A., 2006, Magma-maintained rift segmentation at House Ranges: Brigham Young University Geology Studies, U.S. Geological Survey and Utah Geological Survey, 2006, Qua- continental rupture in the 2005 Afar dyking episode: Nature, v. 27, no. 2, p. 123–139. ternary fault and fold database of the United States: http:// v. 442, p. 291–294, https://doi.org/10.1038/nature04978. Planke, S., and Smith, R.B., 1991, Cenozoic extension and evolu- earthquake.usgs .gov /hazards /qfaults/ (accessed January 2018). York, J.E., and Helmberger, D.V., 1973, Low-velocity zone tion of the Sevier Desert Basin, Utah, from seismic reflection, Valastro, S., Jr., Davis, E.M., and Varela, A.G., 1972, University variations in the southwestern United States: Journal of gravity, and well log data: Tectonics, v. 10, p. 345–365, of Texas at Austin radiocarbon dates IX: Radiocarbon, v. 14, Geophysical Research, v. 78, p. 1883–1886, https://doi.org https://doi.org/10.1029/90TC01948. p. 461–485, https://doi.org/10.1017/S0033822200059506. /10.1029/JB078i011p01883. Rowland, J.V., Baker, E., Ebinger, C.J., Keir, D., Kidane, T., Biggs, Valentine, G.A., and Perry, F.V., 2007, Tectonically controlled, Yuan, X.P., Christie-Blick, N., and Braun, J., 2018, Mechanical J., Hayward, N., and Wright, T.J., 2007, Fault growth at a time-predictable basaltic volcanism from a lithospheric properties of the Sevier Desert detachment: An appli- nascent slow-spreading ridge: 2005 Dabbahu rifting episode, mantle source (central Basin and Range Province, USA): cation of critical Coulomb Wedge theory: Geophysical Afar: Geophysical Journal International, v. 171, p. 1226–1246, Earth and Planetary Science Letters, v. 261, p. 201–216, Research Letters, v. 45, p. 7417−7424, https://doi .org /10.1029 https://doi.org/10.1111/j.1365-246X.2007.03584.x. https://doi.org/10.1016/j.epsl.2007.06.029. /2017GL076854. Rowland, J.V., Wilson, C.J.N., and Gravley, D.M., 2010, Spatial Valentine, G.A., Cortés, J.A., Widom, E., Smith, E.I., Rasoazana- Zeng, Y.H., and Shen, Z.-K., 2017, A fault-based model for crustal and temporal variations in magma-assisted rifting, Taupo mparany, C., Johnsen, R., Briner, J.P., Harp, A.G., and Turrin, deformation in the western United States based on a com- Volcanic Zone, New Zealand: Journal of Volcanology and B., 2017, Lunar Crater volcanic field (Reveille and Pancake bined inversion of GPS and geologic inputs: Bulletin of Geothermal Research, v. 190, p. 89–108, https://doi .org /10 Ranges, Basin and Range Province, Nevada, USA): Geo- the Seismological Society of America, v. 107, p. 2597–2612, .1016/j.jvolgeores.2009.05.004. sphere, v. 13, p. 391–438, https://doi .org /10 .1130 /GES01428 .1. https://doi.org/10.1785/0120150362.