TRANSVERSE AND LONGITUDINAL SEDIMENT TRANSPORT IN THE EAST-TRENDING MID-NEOPROTEROZOIC UINTA MOUNTAIN GROUP AND BIG COTTONWOOD BASIN, NORTHERN UTAH

The Neoproterozoic Uinta Mountain Group (UMG) and Big Cottonwood Formation (BCF) in northern Utah were deposited in an E-W trending intracratonic rift; within a poorly constrained pre-Sturtian (Chuar-Pahrump?) basin. Detrital zircon studies of ten samples from the UMG and BCF in northern Utah reveal two end member provenance types. The basal Red Pine Shale (upper unit of UMG) at the type section, and the basal BCF in the Wasatch Range contain only Archean and Paleoproterozoic grains between 2.4 and 3.4 Ga. All other sampled facies (distal Red Pine Shale, Mount Watson Formation, Hades Pass quartzite, formation of Outlaw Trail, and Jesse Ewing Canyon Formation) contain mainly Proterozoic grain populations, with subordinate Archean grains. The Proterozoic age groups include 1.6 to 1.8 Ga grains likely derived from the Mazatzal terrane, 1.4 to 1.45 Ga grains likely derived from transcontinental anorogenic granites and overlying rhyolite, 0.97 to 1.25 Ga grains of loose “Grenville” affinity, and in two samples, 0.75 to 0.77 Ga grains that constrain the maximum depositional age.

Together with paleocurrent information, the detrital zircon data indicate that parts of the BCF-UMG basin were fed by south-flowing streams draining the Wyoming Province, and that the bulk of the strata were fed by west and north flowing streams with sources in Colorado, southern Utah, and points farther east and(or) south (Llanoria, and/or Grand Canyon area recycled).

Specifically, delta-front deposits in the Red Pine Shale on the north flank of the Uinta range reflect local drainages entering from the north (Wyoming Province), as does the basal Big Cottonwood Formation. Pro-delta deposits in the Red Pine Shale 30 km southward also contain Mazatzal, anorogenic granite, and “Grenville-age” grains that came from the south and east via longshore drift and/or fluvial transport.