title: Active microbial sulfur disproportionation in the Mesoproterozoic.
abstract: The environmental expression of sulfur compound disproportionation has been placed between 640 and 1050 million years ago (Ma) and linked to increases in atmospheric oxygen. These arguments have their basis in temporal changes in the magnitude of 34S/32S fractionations between sulfate and sulfide. Here, we present a Proterozoic seawater sulfate isotope record that includes the less abundant sulfur isotope 33S. These measurements imply that sulfur compound disproportionation was an active part of the sulfur cycle by 1300 Ma and that progressive Earth surface oxygenation may have characterized the Mesoproterozoic.
authors.affiliation: Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742, USA. dtj@geol.umd.edu
authors.forename: David T
authors.initials: DT
authors.lastname: Johnston
authors.forename: Boswell A
authors.initials: BA
authors.lastname: Wing
authors.forename: James
authors.initials: J
authors.lastname: Farquhar
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Kaufman
authors.forename: Harald
authors.initials: H
authors.lastname: Strauss
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Lyons
authors.forename: Linda C
authors.initials: LC
authors.lastname: Kah
authors.forename: Donald E
authors.initials: DE
authors.lastname: Canfield
mesh_terms: D004777:Environment; D005057:Eukaryotic Cells / Q000378:metabolism; D019419:Evolution, Planetary; D019015:Geologic Sediments; D010084:Oxidation-Reduction; D010100:Oxygen; D011387:Prokaryotic Cells / Q000378:metabolism; D012623:Seawater; D013455:Sulfur / Q000378:metabolism; D013460:Sulfur Isotopes
chemical_list: D013460:Sulfur Isotopes; D013455:Sulfur; D010100:Oxygen