Regional structure and kinematic history of the Sevier fold-and-thrust belt, central Utah

Abstract

The Canyon Range, Pavant, Paxton, and Gunnison thrust systems in central Utah form the Sevier fold-and-thrust belt in its type area. The Canyon Range thrust carries an ~12-km-thick succession of Neoproterozoic through Triassic sedimentary rocks and is breached at the surface by the Neogene extensional Sevier Desert detachment fault. The Pavant, Paxton, and Gunnison thrusts carry Lower Cambrian through Cretaceous strata and have major footwall detachments in weak Jurassic rocks. The Canyon Range thrust was active during latest Jurassic-Early Cretaceous time. The Pavant thrust sheet was emplaced in Albian time, formed an internal duplex beneath the Canyon Range during the Cenomanian, and then developed a frontal duplex during the Turonian. The Paxton thrust sheet was initially emplaced during the Santonian, and subsequently formed the Paxton duplex during the early to mid-Campanian. Some slip on the Paxton system was fed into a frontal triangle zone along the Sanpete Valley antiform. The Gunnison thrust system became active in late Campanian time and continued to feed slip into the frontal triangle zone through the early Paleocene. The Canyon Range and main Pavant thrust sheets experienced long-distance eastward transport (totaling >140 km) mainly because they are composed of relatively strong rocks, whereas the eastern thrust sheets accommodated less shortening and formed multiple antiformal duplexes in order to maintain suffi cient taper for continued forward propagation of the fold-and-thrust belt. Total shortening was at least 220 km. Upper crustal thickening of ~16 km produced crust that was >50 km thick and a likely surface elevation >3 km in western Utah. Shortening across the entire Cordilleran retroarc thrust belt at the latitude of central Utah may have exceeded 335 km. The Late Cretaceous paleogeography of the fold-and-thrust belt and foreland basin was similar to the modern central Andean fold-and-thrust belt, with a high-elevation, low-relief hinterland plateau and a rugged topographic front. The frontal part of the Sevier belt was buried by several kilometers of nonmarine and shallowmarine sediments in the wedge-top depozone of the foreland basin system. The Canyon Range thrust sheet dominated sediment supply throughout the history of shortening in the Sevier belt. Westward underthrusting of a several hundred-kilometer-long panel of North American lower crust beneath the Cordilleran magmatic arc is required to balance upper-crustal shortening in the thrust belt, and may be petrogenetically linked to a Late Cretaceous fl are-up of the magmatic arc as preserved in the Sierra Nevada Batholith.

Observations from the Basin and Range Province (western United States) pertinent to the interpretation of regional detachment faults

“…Our re-evaluation of the subsurface data is inconsistent with a related second pillar of the detachment hypothesis: that as much as 47 km of normal slip is needed to account for the offset of Coogan & DeCelles 1996Stockli et al 2001;DeCelles & Coogan 2006). Both the Pavant thrust and the structurally higher Canyon Range thrust are erosionally truncated at the western margin of the southern SDB (Fig.…”

“…1; see also Figs 2 & 3) (McDonald 1976;Allmendinger et al 1983;Smith & Bruhn 1984;Von Tish et al 1985;Mitchell & McDonald 1986, 1987Planke & Smith 1991;Otton 1995;Coogan & DeCelles 1996;Stockli et al 2001) is now largely published Thelin & Pike (1991). (Anders & Christie-Blick 1994;Wills & Anders 1999;Anders et al 2001;Wills et al 2005; for a discussion of contrasting views, see Allmendinger & Royse 1995;Anders et al 1995Anders et al , 1998aWills & Anders 1996;Otton 1996;Coogan & DeCelles 1998;Hintze & Davis 2003;DeCelles & Coogan 2006). Here, we summarize the evidence for an alternative interpretation: that the purported detachment is instead a regional unconformity of Palaeogene age (Gradstein et al 2004) fortuitously aligned down dip in some seismic reflection profiles with a Mesozoic thrust fault.…”

Regional crustal-scale structures as conduits for deep geothermal upflow

“…The Wasatch Front may have developed as a major tectonic boundary as early as the late Proterozoic, associated with rift structures during rifting and the formation of the passive continental margin of Laurentia (Allmendinger et al, 1987;Bissell, 1974;Burchfiel et al, 1992;Dalziel, 1997;Karlstrom et al, 1999;Stewart, 1972), although isotopic studies have shown that the terminal edge of the craton lies farther to the east (Crafford and Grauch, 2002;Grauch et al, 2003;Wooden et al, 1998). The Wasatch Front was also active as the fulcrum for subsidence of the Laurentian passive margin to the west during late Proterozoic though the Triassic (Bissell, 1974;Stewart, 1980) and was subsequently reactivated in the Jurassic-Cretaceous as an axis of thrusting during the Sevier orogeny (DeCelles and Coogan, 2006). The Sevier belt may have been connected to the contemporaneous Luning-Fencemaker thrust system in central Nevada (Fig.…”

The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

“…McQuarrie and Chase (2000) referred to the elevated thick crust in the hinterland of the Sevier fold-thrust belt in western Utah and eastern Nevada (Figure 1) as the 'Sevier Plateau'. In a review of the Cordilleran thrust belt, (DeCelles 2004, p. 147; see also DeCelles and Coogan 2006) referred to this hinterland as the 'Nevadaplano' whose crustal thickness was 50-60 km and palaeo-elevation was more than 3 km. (Coney and Harms 1984).…”