FACIES CONTROL ON DETRITAL ZIRCON PROVENANCE SIGNATURES, NEOPROTEROZOIC RED CASTLE FORMATION, UINTA MOUNTAINS, UTAH

In the Mount Powell quadrangle of the central Uinta Mountains, the Red Castle Formation (Neoproterozoic Uinta Mountain Group) contains five depofacies: 1) braided fluvial, 2) tidally influenced braid delta, 3) and three marine facies distinguished by grain size and lithology. Detrital zircon U-Pb ages from these strata (6 samples, 100 grains each) reflect two provenance signatures- Archean (strong peak >2600 Ma), and one mixed, which includes Grenville (broad population between 1140 and 1205 Ma), Paleoproterozoic (peaks at 1660 and 1850 Ma), and Neoarchean (2640 to 2740 Ma) age populations. The early Paleoproterozoic and Archean provenance was the southern Wyoming craton to the north, where different drainages tapped source areas of distinct ages. The mixed provenance reflects long-distance westward transport of Laurentian Proterozoic zircons mixed with north-derived Archean grains.

Both the braided fluvial and tidally influenced braid delta facies contain the exclusively early Paleoproterozoic and Archean detrital zircon signature. This reinforces the interpretation that the lower and middle members of the Red Castle Formation represent a south-flowing braided fluvial system feeding a braid delta that emptied into the Uinta Mountain Group seaway.

All three of the marine facies are associated with the mixed detrital zircon signature. This supports the interpretation that the upper member of the Red Castle Formation- comprised of both the marine and fluvial facies- records mixing of sediments in the braid delta with those of the shoreline and nearshore marine depositional environments. These trends are consistent with provenance and depofacies trends previously reported from other units of the Uinta Mountain Group.