| Geologic mapping and detrital zircon analysis of rocks exposed within the Bayhorse and Bayhorse Lake quadrangles in central Idaho has identified a slightly metamorphosed yet intact ~1.5 km thick stratigraphic section of Neoproterozoic argillaceous and dolomitic rocks, which overlie in stratigraphic continuum a 667 Ma tuff in a borehole and correlate to the upper Pocatello Formation, Blackrock Canyon Limestone, and Papoose Creek Formation of southeast Idaho. This fine-grained succession is overlain by a gradational contact with a ~1 km thick coarse-grained, Neoproterozoic and Cambrian siliciclastic unit which correlates to the thick Neoproterozoic/Cambrian quartzites of the Caddy Canyon through Camelback Mountain formations of southeast Idaho and northern Utah suggesting correlative Cryogenian and Ediacaran strata are present west of the Lemhi arch from Edwardsburg to Bayhorse to Pocatello. However, at Bayhorse much of the Upper Cambrian and Lower Ordovician section is missing with Middle Ordovician rocks unconformably overlying Middle Cambrian rocks. About 50 km northeast of Bayhorse, Middle Ordovician Kinnikinic Quartzite lies in angular unconformity above Mesoproterozoic Belt Supergroup rocks, defining the Lemhi arch unconformity. This Late Cambrian unconformity possibly correlates with the newly documented unconformity in the Bayhorse region.
Key Words: Rodinia, Neoproterozoic, Lemhi arch, Bayhorse, Rifting, Windermere Supergroup |