Geological Society of America

T214 New Voices in Geobiology

Thursday, 29 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

ALL ABOUT THAT BACE: INTERPRETING THE CARBON ISOTOPE RECORD OF THE EDIACARAN–CAMBRIAN TRANSITION

Paper number: T214-2
Program: Technical Sessions
Time: 1:35 PM – 1:50 PM

Authors

Emily F. Smith Presenting Author
Johns Hopkins University, Baltimore, MD
John A. Higgins
Princeton University, Princeton, NJ
Jahandar Ramezani
Massachusetts Institute of Technology, Cambridge, MA
Mary C. Lonsdale
Johns Hopkins University, Baltimore, MD
Lyle L. Nelson
Johns Hopkins University, Baltimore, MD
Anne-sofie Ahm
Princeton University, Princeton, NJ
Blake Hodgin
Harvard University, Cambridge, MA
Blake Hodgin
University of California Berkeley, Berkeley, CA
Lucy C. Webb
Johns Hopkins University, Baltimore, MD
Uyanga Bold
Mongolian University of Science and Technology, Ulaanbaatar
Dana Brenner
Johns Hopkins University, Baltimore, MD
Mark Schmitz
Boise State University, Boise, ID

Abstract

Latest Ediacaran to early Cambrian carbonate strata record high frequency and high magnitude variability in carbon isotopic values (δ¹³C) within stratigraphic sections globally. This interval of instability in δ¹³C 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 δ¹³C 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 (δ^44/40Ca and δ²⁶Mg values and trace element ratios) are paired with δ¹³Cand 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 δ¹³C_carb records from these successions.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-356511

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