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Bacterial sulfur disproportionation constrains timing of Neoproterozoic oxygenation

Marcus Kunzmann, Thi Hao Bui, Peter W. Crockford, Galen P. Halverson, Clint Scott, Timothy W. Lyons and Boswell A. Wing
Bacterial sulfur disproportionation constrains timing of Neoproterozoic oxygenation
Geology (Boulder) (January 2017) 45 (3): 207-210


Various geochemical records suggest that atmospheric O (sub 2) increased in the Ediacaran (635-541 Ma), broadly coincident with the emergence and diversification of large animals and increasing marine ecosystem complexity. Furthermore, geochemical proxies indicate that seawater sulfate levels rose at this time too, which has been hypothesized to reflect increased sulfide oxidation in marine sediments caused by sediment mixing of the newly evolved macrofauna. However, the exact timing of oxygenation is not yet understood, and there are claims for significant oxygenation prior to the Ediacaran. Furthermore, recent evidence suggests that physical mixing of sediments did not become important until the late Silurian. Here we report a multiple sulfur isotope record from a ca. 835-630 Ma succession from Svalbard, further supported by data from Proterozoic strata in Canada, Australia, Russia, and the United States, in order to investigate the timing of oxygenation. We present isotopic evidence for onset of globally significant bacterial sulfur disproportionation and reoxidative sulfur cycling following the 635 Ma Marinoan glaciation. Widespread sulfide oxidation helps to explain the observed first-order increase in seawater sulfate concentration from the earliest Ediacaran to the Precambrian-Cambrian boundary by reducing the amount of sulfur buried as pyrite. Expansion of reoxidative sulfur cycling to a global scale also indicates increasing environmental O (sub 2) levels. Thus, our data suggest that increasing atmospheric O (sub 2) levels may have played a role in the emergence of the Ediacaran macrofauna and increasing marine ecosystem complexity.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 45
Serial Issue: 3
Title: Bacterial sulfur disproportionation constrains timing of Neoproterozoic oxygenation
Affiliation: McGill University, Department of Earth and Planetary Sciences, Montreal, QC, Canada
Pages: 207-210
Published: 20170109
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 32
Accession Number: 2017-012087
Categories: Isotope geochemistryStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2017054
Illustration Description: illus.
Secondary Affiliation: U. S. Geological Survey, USA, United StatesUniversity of California at Riverside, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201709
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