T346 The Co-Evolution of Life and Its Environment during the Precambrian: The Late Proterozoic Rise of Animals; Climate, Tectonic, and Environmental Dynamics, and the Transition into the Early Paleozoic

Wednesday, 25 October 2017
1:30 PM - 5:30 PM
Skagit 5

MULTIPLE SULFUR ISOTOPIC RECORDS ASSOCIATED WITH THE “SHURAM EXCURSION” FROM SOUTH CHINA

Paper number: T346-12
Program: Technical Sessions
Time: 4:15 PM – 4:30 PM

Authors

  • Jing Huang Presenting Author
    University of Science and Technology of China, Hefei
  • James Farquhar
    University of Maryland, College Park, MD
  • Yanan Shen
    University of Science and Technology of China, Hefei

Abstract

The Ediacaran carbonates record the largest carbon isotopic excursion in Earth history globally. This anomaly implies a dramatic change of the Ediacaran oceanic chemistry, which was closely related to the oceanic/atmospheric oxidation and early animal evolution. The low δ13C values (down to -12‰) in the carbonates were thought to have derived predominately from the oxidation of organic carbon reservoir, and sulfate would be one of the most important oxidants. We report multiple sulfur isotopic data (Δ33S and δ34S) of pyrite from the Doushantuo carbonates in South China. In our study, we find a Δ33S negative excursion from about 0.04‰ to -0.04‰ coupled with a positive δ34S excursion in the upper Doushantuo Formation where the Shuram excursion is exhibited. Our data of multiple S-isotopes suggest that the sulfate level in the ocean may have greatly declined as a result of the long-term oxidation of organic carbon during the “Shuram excursion”. As well, the negative Δ33S compositions imply potential mixing of sulfide from two sources: sulfide produced by sulfate reduction in the relatively open shallow water, with negative δ34S values and positive Δ33S values, and sulfide produced by quantitative sulfate reduction in the relatively closed bottom/pore water, with isotopically similar to seawater sulfate.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-306932

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.