GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 221-13
Presentation Time: 5:00 PM


NELSON, L.L.1, RAMEZANI, J.2, ALMOND, J.E.3, TAYLOR, W.L.4, BRENNER, D.C.5 and SMITH, E.F.5, (1)Department of Earth and Planetary Sciences, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, (2)Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, (3)Natura Viva cc, PO Box 12410 Mill Street, Cape Town, 8010, South Africa, (4)Department of Geological Sciences, University of Cape Town, Private Bag X3, Rondebosch, 7701, South Africa, (5)Department of Earth and Planetary Sciences, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218

The Ediacaran–Cambrian boundary (~539 million years ago) marks a critical biological transition in Earth history: the disappearance of the Ediacaran biota – Earth’s earliest complex macroscopic life forms – from the fossil record and the subsequent radiation of modern animal phyla during the Cambrian Period. This interval in Earth history has also been linked to broadly coeval environmental and ecological changes. Despite a diversity of mechanistic hypotheses regarding the nature and drivers of environmental and biological change across this boundary, high-resolution radioisotopic age models consistently surface as one of the limiting factors to rigorously testing these theories.

Here, we present integrated data from the Neint-Nababeep Plateau along the Orange River in northwestern South Africa, which preserves a newly recognized Ediacaran–Cambrian shallow-marine stratigraphic record. These strata can be used to construct a high-resolution temporal framework of this interval, and preliminary results from this succession include geologic mapping, paleontology, stable isotope geochemistry, and high-precision U-Pb geochronology. We compare these data to other coeval data sets globally to test the hypothesis that there was a synchronous perturbation to seawater chemistry at the Ediacaran–Cambrian boundary.