The Ediacaran–Cambrian transition in the southern Great Basin, United States

Emily (Emmy) Smith
Johns Hopkins University

Ediacaran–Cambrian boundary strata in the Great Basin of the southwestern United States record evidence for biological, geochemical, and tectonic change during the transformative interval of Earth history in which metazoans diversified. In this talk, I will present integrated chemostratigraphy, paleontology, geochronology, sedimentology, and stratigraphy data sets from a ~300 km transect across southeastern California and southwestern Nevada. I will discuss the large negative carbon isotope (δ13C) excursion—also known as the Basal Cambrian Excursion, or BACE—which is regionally reproducible, consistent with a primary marine origin for this perturbation. Ediacaran body fossils are rare across the region but are present and preserved in a variety of taphonomic modes. These occurrences are placed within a regional stratigraphic framework and used to consider the relationships among taphonomic modes for fossil preservation and paleoenvironmental settings within this basin. I will discuss potential relationships among sedimentological features, Ediacaran–Cambrian biotic turnover, and environmental perturbations. Finally, I will present geochronology data that help to constrain the tempo of the BACE and of early Cambrian radiation.