Downloaded from gsabulletin.gsapubs.org on January 26, 2010 Geological Society of America Bulletin Regional structure and kinematic history of the Sevier fold-and-thrust belt, central Utah Peter G. DeCelles and James C. Coogan Geological Society of America Bulletin 2006;118;841-864 doi: 10.1130/B25759.1 Email alerting services click www.gsapubs.org/cgi/alerts to receive free e-mail alerts when new articles cite this article Subscribe click www.gsapubs.org/subscriptions/ to subscribe to Geological Society of America Bulletin Permission request click http://www.geosociety.org/pubs/copyrt.htm#gsa to contact GSA Copyright not claimed on content prepared wholly by U.S. government employees within scope of their employment. 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Notes Geological Society of America Downloaded from gsabulletin.gsapubs.org on January 26, 2010 Regional structure and kinematic history of the Sevier fold-and-thrust belt, central Utah Peter G. DeCelles† Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA James C. Coogan‡ Department of Geology, Western State College of Colorado, Gunnison, Colorado 81231, USA ABSTRACT that was >50 km thick and a likely surface the Idaho state line (Fig. 1). Subsequent work by elevation >3 km in western Utah. Shorten- many authors has shown that contemporaneous The Canyon Range, Pavant, Paxton, and ing across the entire Cordilleran retroarc thrust systems (in the sense of Boyer and Elliott, Gunnison thrust systems in central Utah thrust belt at the latitude of central Utah may 1982) continue for ~3000 km to the north into form the Sevier fold-and-thrust belt in its have exceeded 335 km. The Late Cretaceous northwestern Canada. Thus, the Sevier belt may type area. The Canyon Range thrust carries paleogeography of the fold-and-thrust belt be regarded as a segment of the larger Cordille- an ~12-km-thick succession of Neoprotero- and foreland basin was similar to the modern ran retroarc fold-and-thrust belt (Fig. 1), which zoic through Triassic sedimentary rocks and central Andean fold-and-thrust belt, with a formed during late Mesozoic through Eocene is breached at the surface by the Neogene high-elevation, low-relief hinterland plateau time along the inboard side of the Cordilleran extensional Sevier Desert detachment fault. and a rugged topographic front. The frontal magmatic arc and various allochthonous ter- The Pavant, Paxton, and Gunnison thrusts part of the Sevier belt was buried by sev- ranes (see reviews by Burchfi el et al., 1992; All- carry Lower Cambrian through Cretaceous eral kilometers of nonmarine and shallow- mendinger, 1992; Miller et al., 1992; Dickinson, strata and have major footwall detachments marine sediments in the wedge-top depozone 2004; DeCelles, 2004). in weak Jurassic rocks. The Canyon Range of the foreland basin system. The Canyon Although many of the geometric details of thrust was active during latest Jurassic–Early Range thrust sheet dominated sediment sup- the Sevier belt in central Utah are well docu- Cretaceous time. The Pavant thrust sheet was ply throughout the history of shortening in mented, the regional kinematic history and the emplaced in Albian time, formed an internal the Sevier belt. Westward underthrusting relationships between shortening in the Sevier duplex beneath the Canyon Range during of a several hundred-kilometer-long panel belt and tectonic processes in the Cordilleran the Cenomanian, and then developed a fron- of North American lower crust beneath the magmatic arc and hinterland region remain tal duplex during the Turonian. The Paxton Cordilleran magmatic arc is required to bal- obscure. The most recent synthesis of regional thrust sheet was initially emplaced during ance upper-crustal shortening in the thrust structure and kinematic history in the Sevier the Santonian, and subsequently formed the belt, and may be petrogenetically linked to a belt of central Utah is now nearly two decades Paxton duplex during the early to mid-Cam- Late Cretaceous fl are-up of the magmatic arc old (Villien and Kligfi eld, 1986). Numerous panian. Some slip on the Paxton system was as preserved in the Sierra Nevada Batholith. more recent studies have provided abundant fed into a frontal triangle zone along the San- new information on the structural geology, kine- pete Valley antiform. The Gunnison thrust Keywords: Cordilleran tectonics, fold-and- matic history, and erosional unroofi ng history of system became active in late Campanian thrust belts, foreland basins, Utah. the region (e.g., Royse, 1993; DeCelles et al., time and continued to feed slip into the fron- 1995; Lawton et al., 1997; Mitra, 1997; Stockli tal triangle zone through the early Paleocene. INTRODUCTION et al., 2001; Currie, 2002; Hintze and Davis, The Canyon Range and main Pavant thrust 2002, 2003; Ismat and Mitra, 2001, 2005), such sheets experienced long-distance eastward The Sevier fold-and-thrust belt in central Utah that a revised synthesis is overdue. The purpose transport (totaling >140 km) mainly because (western interior USA) is the type area of one of of this paper is to provide such a synthesis. We they are composed of relatively strong rocks, the world’s classic fold-and-thrust belts and was draw upon subsurface data, new mapping, new whereas the eastern thrust sheets accom- among the fi rst to be systematically character- chronostratigraphic constraints on the ages of modated less shortening and formed mul- ized in terms of modern concepts of thrust-belt proximal synorogenic sediments derived from tiple antiformal duplexes in order to main- geology and geophysics (Armstrong and Oriel, the Sevier belt, and recent thermochronological tain suffi cient taper for continued forward 1965; Armstrong, 1968; Dahlstrom, 1970; studies to develop a sequential kinematic resto- propagation of the fold-and-thrust belt. Royse et al., 1975; Burchfi el and Davis, 1975; ration of the fold-and-thrust belt. The regional Total shortening was at least 220 km. Upper Lamerson, 1982; Allmendinger et al., 1983, balanced cross section that forms the basis for crustal thickening of ~16 km produced crust 1986, 1987; Smith and Bruhn, 1984). Armstrong this restoration was constructed using a com- (1968) defi ned the Sevier belt as the linear group bination of GeoSec and LithoTect software. †E-mail: [email protected]. of closely spaced thrust faults and related folds Thrust-related deformation was modeled using ‡E-mail: [email protected]. that extends from the Las Vegas, Nevada, area to a fl exural slip algorithm for fault-bend folds. GSA Bulletin; July/August 2006; v. 118; no. 7/8; p. 841–864; doi: 10.1130/B25759.1; 12 fi gures. For permission to copy, contact [email protected] 841 © 2006 Geological Society of America Downloaded from gsabulletin.gsapubs.org on January 26, 2010 DeCelles and Coogan Precambrian shear zones and crustal boundaries in the widest part of the Cordilleran orogenic Accretionary complexes belt, where major thrust faults form an enor- Cordilleran magmatic arc mous eastward-convex salient with a north- Antler and Sonoma orogenic terranes south chord length of 1500 km. The Cordil- Outcrop areas of Jurassic-Cretaceous mid-crustal metamorphic rocks leran magmatic arc formed along the western Sevier fold-thrust belt (expanded) margin of the North American plate in response Laramide foreland province to eastward subduction of oceanic plates from Major thrust fault, barbs Late Triassic to Late Cretaceous time (e.g., British Columbia on hanging wall Hamilton, 1969; Dickinson, 1976; Saleeby and Intraforeland arch Busby-Spera, 1992). The roots of the arc are Major synform exemplifi ed by the Sierra Nevada Batholith, a 500 km 40 × 103 km2 body of granodiorite and tonalite 120° 112° 104°W Alberta Canada 49°N that forms the bulk of the Sierra Nevada. The Montana U.S.A. batholith developed over an ~140 m.y. time span beginning at 220 Ma (Bateman, 1983; Barton et al., 1988; Barton, 1996; Coleman and Glazner, 1998; Ducea, 2001). Washington Directly east of the Sierra Nevada Batholith Idaho 45° lies the Luning-Fencemaker thrust belt (Fig. 1), batholith which is mainly composed of Triassic fi ne- in la grained, deep-marine facies (Elison and Speed, P er iv 1988; Oldow et al., 1990) that were tectoni- R ke cally transported eastward and southeastward Sri =0.706 na Oregon S by imbricate thrust faults and emplaced upon California Idaho Nevada autochthonous shallow-marine shelf facies dur- ° Wyoming 41 ing Middle Jurassic to Early Cretaceous time Colorado UU (Speed, 1978; Oldow, 1983, 1984; Wyld, 2002). G Total shortening of 50%–75% (amounting to C CR r e LFTB N a T perhaps ~75–180 km) was accompanied by O t V B S a low-grade metamorphism (Wyld, 2002). Based l l a e n y A on partial overlap in the timing of shortening in f n o d r r e ° the Luning-Fencemaker and Sevier belts, Oldow e a Utah 37 a r s c New Mexico (1983, 1984) and Speed et al. (1988) suggested fa b Arizona u a s lt that the two thrust belts shared a common, mid- in ESTB crustal décollement and bracketed a broad region CM in Nevada and western Utah that was relatively little deformed.