Paper No. 214-1
Presentation Time: 1:35 PM
ALL ABOUT THAT BACE: INTERPRETING THE CARBON ISOTOPE RECORD OF THE EDIACARAN–CAMBRIAN TRANSITION (Invited Presentation)
SMITH, Emily F.1, LONSDALE, Mary C.1, NELSON, Lyle L.1, AHM, Anne-Sofie C.2, HODGIN, Eben B.3, WEBB, Lucy C.1, BOLD, Uyanga4, BRENNER, Dana C.1, SCHMITZ, Mark D.5, HIGGINS, John A.2 and RAMEZANI, Jahandar6, (1)Department of Earth and Planetary Sciences, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, (2)Department of Geosciences, Princeton University, Washington Road, Guyot Hall, Princeton, NJ 08544, (3)Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138; Department of Earth and Planetary Sciences, University of California Berkeley, 307 McCone Hall, Berkeley, CA 94720, (4)School of Geology and Petroleum Engineering, Mongolian University of Science and Technology, Ulaanbaatar, 210349, Mongolia, (5)Department of Geosciences, Boise State University, Boise, ID 83725, (6)Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
Latest Ediacaran to early Cambrian carbonate strata record high frequency and high magnitude variability in carbon isotopic values (δ
13C) within stratigraphic sections globally. This interval of instability in δ
13C values coincides with one of the greatest geobiological transitions in Earth history: the disappearance of Ediacaran organisms and the evolution and diversification of modern animal phyla. Although the causal mechanisms behind these δ
13C excursions are still debated, geoscientists have relied heavily on chemostratigraphic curves to construct age models and have related perturbations of the carbon cycle to evolutionary change.
We aim to test the hypothesis that the δ13C excursions across the Ediacaran–Cambrian transition reflect the composition of dissolved inorganic carbon in global oceans and are buffered from post-depositional diagenetic effects. First, radioisotopic data (U-Pb on zircon) from different continental margins are used to test global synchroneity and duration of individual excursions. Second, geochemical tracers of marine diagenesis (δ44/40Ca and δ26Mg values and trace element ratios) are paired with δ13C and δ18O data to evaluate possible regional controls on these carbonate isotopic records. We present integrated datasets from Mongolia, South Africa, the southwest USA, and northern Mexico, and discuss our current understanding of how to interpret δ13Ccarb records from these successions.
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