Maximum depositional age and provenance of the Uinta Mountain Group and Big Cottonwood Formation, northern Utah: Paleogeography of rifting western Laurentia

Abstract

U-Pb detrital zircon analyses provide a new maximum depositional age constraint on the Uinta Mountain Group (UMG) andcorrelative Big Cottonwood Formation (BCF) of Utah, and signifi cantly enhance our insights on the mid-Neoproterozoic paleogeographic and tectonic setting of western Laurentia. A sandstone interval of the Outlaw Trail formation with a youngest population (n = 4) of detrital zircons, from a sampling of 128 detrital zircon grains, yields a concordia age of 766 ± 5 Ma. This defi nes a maximum age for deposition of the lowermiddle Uinta Mountain Group in the eastern Uinta Mountains and indicates that the group is no older than middle Neoproterozoic in age (i.e., Cryogenian). These data support a long-proposed correlation with the Chuar Group of Grand Canyon (youngest age 742 Ma ± 6 Ma), which, like the Uinta Mountain Group and Big Cottonwood Formation, records nonmagmatic intracratonic extension. This suggests a ~742 to ≤766 Ma extensional phase in Utah and Arizona that preceded the regional rift episode (~670-720 Ma), which led to development of the Cordilleran passive margin. This is likely an intracratonic response to an early rift phase of Rodinia. Further, because the Chuar Group and the Uinta Mountain Group-Big Cottonwood Formation strata record intracratonic marine deposition, this correlation suggests a regional ~740-770 Ma transgression onto western Laurentia.The detrital grain-age distributions from 12 samples include the following grain-age populations and interpreted provenance: 2.5-2.7 Ga (late Archean southern Wyoming province); 1.6-1.8 Ga (Paleoproterozoic Yavapai province); 1.5-1.6 Ga (Early Meso proterozoic North American magmatic gap), 1.4-1.45 Ga (Colorado province A-type granite-rhyolite belt); 0.93-1.2 Ga (eastern Grenvillian orogen); and midNeoproterozoic volcanic grains (766 Ma). Sediment was transported by: (1) a major longitudinal west-fl owing river system tapping the Grenville orogen, (2) local southfl owing drainages off the southern Wyoming craton, and (3) northerly and westerly fl owing marine currents. The Uinta Mountain Group river system was one of several major transcontinental drainages that delivered Grenvillian zircon grains to the protoPacifi c Ocean. We propose that this river system ultimately supplied sediment to periGondwanan margins along the proto-Pacifi c to Antarctica, Australia, and South America, providing an alternative source for explaining the problematic provenance of Grenvillian grains in these areas.

The Great Grenvillian Sedimentation Episode: Record of Supercontinent Rodinia's assembly

“…29.2;Link et al, 1993). A series of provenance studies of these rocks (Condie et al, 2001;Mueller et al, 2007;Dehler et al, 2010) yielded detrital zircon U-Pb age profiles similar to those described above (Fig. 29.8b), and support the idea that this is yet another remnant of the vast drainage network that delivered detritus westward across Laurentia to an epicratonic basin or basins that Fig.…”

“…We consider that the sediments were transported away from the orogeny by a pan-continental river system, the proximal and distal elements of which are preserved in sedimentary basins mainly in North America, Greenland, and the United Kingdom (see Rainbird et al, 1992Rainbird et al, , 1997. Since the publication of the big river model, numerous studies, all of them employing detrital zircon geochronology, have added additional pieces to the puzzle of Rodinian paleogeography (Cawood et al, 2004;Kirkland et al, 2008;Krabbendam et al, 2008;Mueller et al, 2007;Santos et al, 2002;Dehler et al, 2010).…”

“…Probability density diagrams with superimposed histograms of LA-ICPMS detrital zircon U-Pb ages from early Neoproterozoic sandstones from the (a) Nankoweap Formation (Grand Canyon Supergroup; data from Timmons et al, 2005) and the (b) Big Cottonwood Formation, Uinta Mountains Group. Source: Data from Dehler et al, 2010. existed along its western and northern margin (Figs. 29.1 and 29.2).…”

Provenance and tectonic setting of Neoproterozoic sedimentary sequences in the South China Block: evidence from detrital zircon ages and Hf–Nd isotopes

“…In the past decades, detrital zircons become an important tool to constrain the depositional ages and possible source terranes of sedimentary rocks, and thus to investigate the reconstruction of supercontinents (DeGraaff-Surpless et al 2002;Fedo et al 2003;Wang et al 2007;Jones et al 2009;Dehler et al 2010;Wang et al 2010c). Combining U-Pb ages and Hf isotope composition, detrital zircons can provide an important record on provenance as well as on the characteristic of source rocks (Griffin et al 2004;Wu et al 2007;Liu et al 2008;Wang et al 2010a, b).…”

Geology, Mantle Tomography, and Inclination Corrected Paleogeographic Trajectories Support Westward Subduction During Cretaceous Orogenesis in the North American Cordillera

“…Some workers (Lund 2008;Dehler et al 2010;Balgord et al 2013) suggest that Neoproterozoic rocks of the Windermere Supergroup and its equivalents are rift rocks, but evaporites are unreported, volcanic rocks are very sparse, and overall the rocks are 100-200 Myr older than passive margin subsidence of the North American margin (Bond and Kominz 1984). The lack of such rocks along the entire length of the Cordillera suggests that the rift rocks, along with outer riseslope sedimentary rocks, which are also missing from North America, were not simply displaced by strike-slip faults, but instead torn from the margin during slab failure -a feature readily accounted for in the westerly subduction model, in which North America was attached to a westerly subducting slab, but difficult to reconcile in easterly dipping models (Hildebrand and Bowring 1999;Hildebrand 2009Hildebrand , 2013.…”