Regional correlation, age constraints, and geologic history of the Neoproterozoic-Cambrian Strata, southern Great Basin, United States: Integrated carbon isotope stratigraphy, biostratigraphy, and lithostratigraphy.

摘要

Carbon-isotope chemostratigraphy, shown to be useful for the Neoproterozoic-Cambrian interval, was applied to the pre-trilobite White-Inyo and Death Valley strata (southern Great Basin) in an attempt to correlate and place age constraints on the units. Carbonate samples were taken from across the ancient shelf and subjected to a battery of tests to evaluate the effect of post-depositional alteration and facies control on the isotopic compositions.; Based on carbon-isotope chemostratigraphy in the White-Inyo region, the Wyman Formation is correlated with deposits between 700 Ma and 605 Ma. The Hines Tongue of the Reed Formation is correlated with rocks dated at 548 Ma. The hiatus noted at the Wyman and Reed contact would encompass 57 to 157 million years. The Precambrian-Cambrian boundary is between the Lower and Middle Deep Spring, at 544 Ma.; In the Death Valley region, the Kingston Peak Formation is interpreted to be between 766 Ma and 723 Ma. The Noonday Dolomite through the upper-carbonate bearing member of the Johnnie Formation is correlated to units between 723 Ma and ∼700 Ma. The Rainstorm Member of the Johnnie is interpreted to be younger than 595 Ma, suggesting that a hiatus of over 100 million years is present within the Johnnie. The Stirling through lowermost Wood Canyon may correlate with rocks dated ∼545 Ma. Therefore, the incision at the top of the Johnnie may represent ∼50 million years. The Precambrian-Cambrian boundary is within the Lower Wood Canyon, based on the presence of Phycodes pedum. The association of Phycodes pedum with the isotopes allows chemostratigraphic correlation of the boundary from the siliciclastic type section in Newfoundland to carbonate-dominated sections elsewhere.; Based on the isotopic data, the Wyman Formation correlates with the sub-Rainstorm Johnnie Formation. The Lower Reed Formation correlates directly with the D member of the Stirling, but the Stirling A, B, and C members are not represented in the White-Inyo region. The incision surface at the top of the Wyman Formation correlates with the surface at the top of the Johnnie Formation. The carbonate units in the Lower Wood Canyon and the Deep Spring Formation correlate in a gross sense, but are shown to be diachronous across the shelf.