Proterozoic Paleogeography and Stratigraphy of the Snake Range, Eastern Nevada and Albion-Grouse Creek Ranges, Southern Idaho: Detrital Zircon Constraints and Stratigraphic Surprises

We present new detrital zircon data from the Neoproterozoic–Cambrian strata of the northern Snake Range, NV, from Proterozoic quartzites in the Grouse Creek–Albion Range of southern ID, and from the Willard thrust plate in the northern Wasatch Range, UT.

In the northern Snake Range the McCoy Creek Gp has age populations at 1.0, 1.4, 1.6–1.8 and 2.6 Ga. The Cambrian Prospect Mountain Qzte contains a major population of 1.6–1.8 Ga grains and only minor younger populations.

In the Grouse Creek–Albion Range, the basal Elba Qzte contains major populations at 1.0, 1.4, 1.6–1.8 and 2.6 Ga, similar to the McCoy Creek and Brigham Groups, suggesting these units are all part of the miogeocline, as previously thought. The quartzites of Clark's Basin (structurally low) and Harrison Summit (structurally high) have similar detrital zircon populations to the Facer Fm in the northern Wasatch, with major populations of 1.6–1.8 Ga grains, minor 2.6 Ga zircons and no grains less than 1.6 Ga. These units may thus be Paleoproterozoic, and stratigraphically equivalent. They have hitherto been considered Neoproterozoic and Cambrian. More work is needed.

The structurally medial qzte of Yost contains only Archean grains, older than 2.6 Ga. It is thus a unique unit with no known stratigraphic affinities.

The complete absence of detrital grains with 1.0 Ga (Grenville and mid-continent rift) and 1.4 Ga (transcontinental granite–rhyolite) ages in the Grouse Creek–Albion miogeoclinal section suggests emergence of a paleo-Tooele–Uinta Arch by Early Cambrian time (Farmer and Ball, 1997, Condie et al., 2001). This arch, composed of 1.6 to 1.8 Ga magmatic rocks, may have simultaneously acted as a proximal source for Paleoproterozoic sediment northward to the Grouse Creek Basin, as well as a barrier to Mesoproterozoic sediment sources from the southeast, which were confined to the miogeoclinal basins of western UT and NV.