Paleogeographic isolation of the Cretaceous to Eocene Sevier hinterland, east-central Nevada: Insights from U-Pb and (U-Th)/He detrital zircon ages of hinterland strata P. Druschke1,†, A.D. Hanson1, M.L. Wells1, G.E. Gehrels2, and D. Stockli3 1Department of Geoscience, University of Nevada, Las Vegas, Nevada 89154, USA 2Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA 3Department of Geology, University of Kansas, Lawrence, Kansas 66045, USA ABSTRACT cover. Early Cretaceous (ca. 135 Ma) cool- The Late Cretaceous and Paleogene Sevier ing ages are potentially coeval with shorten- hinterland of central Nevada, located west of The Late Cretaceous to Paleogene Sevier ing along the central Nevada fold-and-thrust the foreland fold-and-thrust belt, has previously hinterland of east-central Nevada is widely belt, although ca. 80 Ma cooling ages within been interpreted as a region of high-elevation regarded as an orogenic plateau that has the Sheep Pass Formation are coeval with and low topographic relief, characterized by since undergone topographic collapse. New hinter land midcrustal extension. Together, broad, open folding (Armstrong, 1968, 1972; U-Pb detrital zircon age data consisting of these new data provide support for previous Gans and Miller, 1983; Miller and Gans, 1989; 1296 analyses from the Lower Cretaceous interpretations that the Sevier hinterland DeCelles, 2004). However, Upper Cretaceous Newark Canyon Formation and the Upper represents an ancient high-elevation oro- to Lower Eocene strata of east-central Nevada Cretaceous to Eocene Sheep Pass Formation genic plateau, and that the latest Cretaceous and adjacent Utah are widely interpreted as ex- indicate that Precambrian detrital zircon locally marks a transition from contraction tensional basin deposits (Winfrey, 1958, 1960; populations recycled from local Paleozoic to extension. Kellogg, 1964; Vandervoort and Schmitt, 1990; strata are dominant. Subordinate Mesozoic Fouch et al., 1991; Potter et al., 1995; Camilleri, zircon populations are derived mainly from INTRODUCTION 1996; Dubiel et al., 1996), and surface-breaking local backarc volcanic centers of Late Juras- normal faults of latest Cretaceous age have sic and Early Cretaceous age, while ca. 38– The Late Cretaceous to Paleogene hinter- been documented within the type section of the 36 Ma detrital zircon age peaks record the land of the Sevier retroarc fold-and-thrust belt Sheep Pass Formation (Druschke et al., 2009a). local onset of Eocene volcanism. Sevier is widely interpreted as an ancient orogenic Furthermore, the presence of megabreccia hinter land deposits of east-central Nevada plateau similar to the modern Andean Puna- and boulder-bearing conglomerates within the lack signifi cant Triassic, Early Jurassic, and Altiplano (Coney and Harms, 1984; Jordan and Sheep Pass Formation (Kellogg, 1964; Vander- Late Cretaceous populations common in ter- Alonso, 1987; Allmendinger, 1992; Jones et al., voort and Schmitt, 1990; Druschke et al., 2009a, ranes of western Nevada and the Sierra Ne- 1998; House et al., 2001; DeCelles, 2004). 2009b) indicates areas of locally high relief. In vada magmatic arc. These data suggest that Outcrops of Early Cretaceous to Eocene sedi- our interpretation, Late Cretaceous to Eocene long-term evolution of the Sevier Plateau in- mentary strata scattered across east-central Ne- basins of the Sevier hinterland are analogous to volved geographic isolation through a combi- vada record a transition from Early Cretaceous modern extensional basin systems documented nation of high relief and rugged topography contraction (Allmendinger, 1992; Taylor et al., within the hinterlands of the modern Puna- related to Early Cretaceous shortening, and 2000; DeCelles, 2004) to Late Cretaceous– Altiplano and Tibetan Plateaus (Dalmayrac and continued isolation through development Paleogene extension within the Sevier hinter- Molnar, 1981; Molnar and Chen, 1983; All- of latest Cretaceous to Eocene internally land (Vandervoort and Schmitt, 1990; Camilleri, mendinger et al., 1997; Kapp et al., 2008). drained, extensional basins. 1996; Druschke et al., 2009a, 2009b). Although Previous studies of the Grouse Creek–Raft The (U-Th)/He zircon ages obtained from numerous studies within the Sevier foreland River–Albion, Ruby–East Humboldt, and the Sheep Pass Formation record late Paleo- fold-and-thrust belt and foreland basin system Snake Range metamorphic core complexes zoic, Early Cretaceous, and Late Creta- have established a pattern of sediment accu- (Fig. 1) have documented latest Cretaceous ceous cooling through 180 °C. Preservation mulation and evolving provenance in response and Paleogene midcrustal extension within of late Paleozoic (ca. 265 Ma) cooling ages to changes in the kinematics of the contrac- the Sevier hinter land. Peak Barrovian meta- indicates that much of the Upper Paleozoic tional wedge (e.g., Wiltschko and Dorr, 1983; morphism occurred within hinterland core section within east-central Nevada that con- Allmendinger, 1992; DeCelles, 1994, 2004; complexes during the Late Cretaceous ca. 100– tributed detritus to the Sheep Pass basin DeCelles and Currie, 1996; DeCelles et al., 75 Ma and is interpreted to represent maximum was un affected by deep thrust burial, or by 1995; Lawton et al., 1997; Horton et al., 2004), crustal thickening (Miller et al., 1988; Miller burial beneath thick Mesozoic sedimentary the tectonic and paleogeographic implications and Gans, 1989; Wells, 1997; Lewis et al., of coeval sedimentary deposits within the Sevier 1999; McGrew et al., 2000; Sullivan and Snoke, †E-mail: [email protected] hinterland are poorly understood. 2007; Wells and Hoisch, 2008). Following peak GSA Bulletin; May/June 2011; v. 123; no. 5/6; p. 1141–1160; doi: 10.1130/B30029.1; 10 fi gures; Data Repository item 2011056. For permission to copy, contact [email protected] 1141 © 2011 Geological Society of America Druschke et al. Scale (km) EXPLANATION Figure 1. Map of the western 0200 400 area of predominantly ID Cenozoic cover U.S. Cordillera showing the 42°N OR GRA Cretaceous-Paleogene location of major Paleozoic to Klamath Sevier/Laramide Mesozoic tectonic elements. CA NV foreland basin Cretaceous to Paleogene Box corresponds to area of Sevier fold-thrust belt Figure 2. GA—the Permian- Cretaceous to Paleogene Triassic/Jurassic Triassic Golconda allochthon, RH metamorphic core complex backarc strata GA RMA—the Devonian to Mis- Cretaceous sissippian Roberts Mountain batholith RMA allochthon, CNTB—the Early Triassic to Jurassic SR volcanic strata Cretaceous central Nevada Great Valley CNTB Triassic to Jurassic fold-and-thrust belt, GRA— backarc basin strata the Grouse Creek–Raft River– Sevier fold/thrust belt Sierra Nevada Paleozoic to early Albion core complex, RH—the 37°N Mesozoic accreted terranes Ruby–East Humboldt core Sevier/Laramide foreland Permian-Triassic complex, SR—the Snake Range Pacific Ocean Golconda allochthon Devonian to Mississippian core complex. Figure is modifi ed Coast Ranges Roberts Mountain from Smith and Gehrels (1994); allochthon Transcontinen Wyld (2002); Wells and Hoisch N Paleozoic carbonate ramp/shelf (2008); and Dickinson (2008). tal arch thrust fault, dashed 120°W 114°W where inferred or covered metamorphism , an estimated 14 km of mid- of the Sheep Pass Formation and underlying shelf system to the east (Burchfi el et al., 1992; crustal extensional thinning occurred within the Mississippian strata is used to constrain the Poole et al., 1992; Dickinson, 2000). Grouse Creek–Raft River–Albion and Ruby– shallow crustal thermal history of east-central Subsequent slab rollback within the fring- East Humboldt core complexes beginning in the Nevada. Together, these data offer new insight ing arc system led to initiation of the Antler Late Cretaceous (ca. 75–67 Ma), based on Bar- into the tectonic and paleogeographic evolu- backarc fold-and-thrust belt in latest Devonian rovian metamorphic mineral assemblages and tion of the Sevier hinterland and provide an time (Burchfi el et al., 1992; Dickinson, 2000, thermochronometry (Wells et al., 1990; Hodges analog for long-term processes affecting mod- 2006). During the Antler orogeny, deep-marine and Walker, 1992; Camilleri and Chamberlain, ern orogenic hinterland regions. deposits of the Roberts Mountain allochthon, 1997; Wells et al., 1998; Harris et al., 2007; Wells derived from arc terranes to the west and sedi- and Hoisch, 2008). Although clear evidence for GEOLOGIC BACKGROUND ment shed from the Laurentian craton to the Late Cretaceous midcrustal extension has not east, were thrust up to 200 km eastward onto the been documented in the Snake Range core com- Pre-Mesozoic Framework adjacent carbonate shelf (Roberts et al., 1958; plex, a post–75 Ma lowering of metamorphic Speed and Sleep, 1982; Poole et al., 1992). A gradients and sparse U-Pb monazite ages may Pre-Mesozoic geotectonic terranes of the thick succession of latest Devonian to early indicate Late Cretaceous to early Paleo gene tec- western United States strongly influenced Mississippian clastic sediments, derived from tonic unroofi ng (Lewis et al., 1999). By middle the provenance of Sevier hinterland deposits, the Roberts Mountain allochthon, was de- to late Eocene time (42–36 Ma), all three core given that reworked Paleozoic lithologies are posited in the Antler foreland basin (Roberts complexes experienced signifi cant extension a dominant constituent of Cretaceous to Paleo- et al., 1958; Speed and Sleep, 1982; Poole et al., followed