Journal article
Influence of sulfate reduction rates on the Phanerozoic sulfur isotope record
Proceedings of the National Academy of Sciences of the United States of America, Vol.110(28), pp.11244-11249
Jul/2013
Abstract
Phanerozoic levels of atmospheric oxygen relate to the burial histories of organic carbon and pyrite sulfur. The sulfur cycle remains poorly constrained, however, leading to concomitant uncertainties in O-2 budgets. Here we present experiments linking the magnitude of fractionations of the multiple sulfur isotopes to the rate of microbial sulfate reduction. The data demonstrate that such fractionations are controlled by the availability of electron donor (organic matter), rather than by the concentration of electron acceptor (sulfate), an environmental constraint that varies among sedimentary burial environments. By coupling these results with a sediment bio-geochemical model of pyrite burial, we find a strong relationship between observed sulfur isotope fractionations over the last 200 Ma and the areal extent of shallow seafloor environments. We interpret this as a global dependency of the rate of microbial sulfate reduction on the availability of organic-rich sea-floor settings. However, fractionation during the early/mid-Paleozoic fails to correlate with shelf area. We suggest that this decoupling reflects a shallower paleoredox boundary, primarily confined to the water column in the early Phanerozoic. The transition between these two states begins during the Carboniferous and concludes approximately around the Triassic-Jurassic boundary, indicating a prolonged response to a Carboniferous rise in O-2. Together, these results lay the foundation for decoupling changes in sulfate reduction rates from the global average record of pyrite burial, highlighting how the local nature of sedimentary processes affects global records. This distinction greatly refines our understanding of the S cycle and its relationship to the history of atmospheric oxygen.
Details
- Title
- Influence of sulfate reduction rates on the Phanerozoic sulfur isotope record
- Creators
- William D. Leavitt (null)Itay Halevy (null) - 972WIS_INST___99Alexander S. Bradley (null)David T. Johnston (null)
- Resource Type
- Journal article
- Publication Details
- Proceedings of the National Academy of Sciences of the United States of America, Vol.110(28), pp.11244-11249; Jul/2013
- Number of pages
- 6
- Language
- English
- DOI
- https://doi.org/10.1073/pnas.1218874110
- Grant note
- National Science Foundation (NSF) Graduate Research Fellowship Program; Microbial Sciences Initiative at Harvard; National Aeronautics and Space Administration (NASA)-NASA Astrobiology Institute; NSF Earth Sciences/Instrumentation and Facilities; NSF Faculty Early Career Development Program; Harvard UniversityWe thank A. Pearson for detailed comments that greatly improved this manuscript, C. Cavanaugh, C. Hansel, T. Laakso, and J. C. Creveling for comments that helped along earlier versions of this manuscript, and Tim Lyons and an anonymous reviewer for thoughtful commentary. A. Masterson, E. Beirne, and M. Schmidt provided expert analytical assistance. The National Science Foundation (NSF) Graduate Research Fellowship Program (W.D.L.), Microbial Sciences Initiative at Harvard (W.D.L. and D.T.J.), National Aeronautics and Space Administration (NASA)-NASA Astrobiology Institute, NSF Earth Sciences/Instrumentation and Facilities, NSF Faculty Early Career Development Program, and Harvard University (D.T.J.) all supported this work._ALMAME_DELIMITER_
- Record Identifier
- 993264178703596
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