AGE AND PROVENANCE OF PROXIMAL TERTIARY QUARTZITE COBBLE CONGLOMERATES NEAR JACKSON HOLE, WY USING DETRITAL ZIRCON U/PB GEOCHRONOLOGY

Quartzite conglomerates Late Cretaceous to Eocene in age outcrop in deposits up to 1-4 km thick in areas of Sublette and Teton Counties. Our goal in this research is to characterize the age and provenance of these clasts using detrital zircon U/Pb geochronology. As part of this study, we sampled three different formations (#475; zircon analysis total) at six localities. The Harebell Formation was sampled at along Buffalo Fork (#85) and Pacific Creek (#83). The Pinyon Formation was sampled along Pacific Creek (#=43), in the Gros Ventre Mountains (#=98) and at Hominy Peak (#=82). The Hominy Peak Formation was sampled just south of Hominy Peak (#=84). Meso- and Paleoproteroic zircons dominated these spectra, ranging from 71-91%. Grenville and Archean zircon populations also are present, ranging from 1-15% and 5-18%, respectively. The overlap and similarity indices ranged from 0.62-0.82 and 0.68-0.84, respectively. These data indicate that the protolith sediment of these quartzites were generated in the Yavapai-Mazatzal orogenic belt to the south and east. This sediment was transported to the Neoproterozic continental margin of ID and MT and then metamorphosed. These quartzites were then uplifted during the Sevier Orogeny, were eroded and the clasts were transported eastward into the Western Interior Basin. It is likely that much of this sediment could have been reworked and recycled into younger conglomeratic units. The quartzite clasts studied here have identical detrital zircon spectra to quartzite bearing conglomerates of the Fort Union, Willwood and Wapiti Formations to the east.