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Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2.
Proc Natl Acad Sci U S A. 2013 Nov 12; 110(46):18407-12.PN

Abstract

The Mesozoic Era is characterized by numerous oceanic anoxic events (OAEs) that are diagnostically expressed by widespread marine organic-carbon burial and coeval carbon-isotope excursions. Here we present coupled high-resolution carbon- and sulfur-isotope data from four European OAE 2 sections spanning the Cenomanian-Turonian boundary that show roughly parallel positive excursions. Significantly, however, the interval of peak magnitude for carbon isotopes precedes that of sulfur isotopes with an estimated offset of a few hundred thousand years. Based on geochemical box modeling of organic-carbon and pyrite burial, the sulfur-isotope excursion can be generated by transiently increasing the marine burial rate of pyrite precipitated under euxinic (i.e., anoxic and sulfidic) water-column conditions. To replicate the observed isotopic offset, the model requires that enhanced levels of organic-carbon and pyrite burial continued a few hundred thousand years after peak organic-carbon burial, but that their isotope records responded differently due to dramatically different residence times for dissolved inorganic carbon and sulfate in seawater. The significant inference is that euxinia persisted post-OAE, but with its global extent dwindling over this time period. The model further suggests that only ~5% of the global seafloor area was overlain by euxinic bottom waters during OAE 2. Although this figure is ~30× greater than the small euxinic fraction present today (~0.15%), the result challenges previous suggestions that one of the best-documented OAEs was defined by globally pervasive euxinic deep waters. Our results place important controls instead on local conditions and point to the difficulty in sustaining whole-ocean euxinia.

Authors+Show Affiliations

Department of Earth Sciences, University of California, Riverside, CA 92521.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Historical Article
Journal Article
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

24170863

Citation

Owens, Jeremy D., et al. "Sulfur Isotopes Track the Global Extent and Dynamics of Euxinia During Cretaceous Oceanic Anoxic Event 2." Proceedings of the National Academy of Sciences of the United States of America, vol. 110, no. 46, 2013, pp. 18407-12.
Owens JD, Gill BC, Jenkyns HC, et al. Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2. Proc Natl Acad Sci U S A. 2013;110(46):18407-12.
Owens, J. D., Gill, B. C., Jenkyns, H. C., Bates, S. M., Severmann, S., Kuypers, M. M., Woodfine, R. G., & Lyons, T. W. (2013). Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2. Proceedings of the National Academy of Sciences of the United States of America, 110(46), 18407-12. https://doi.org/10.1073/pnas.1305304110
Owens JD, et al. Sulfur Isotopes Track the Global Extent and Dynamics of Euxinia During Cretaceous Oceanic Anoxic Event 2. Proc Natl Acad Sci U S A. 2013 Nov 12;110(46):18407-12. PubMed PMID: 24170863.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2. AU - Owens,Jeremy D, AU - Gill,Benjamin C, AU - Jenkyns,Hugh C, AU - Bates,Steven M, AU - Severmann,Silke, AU - Kuypers,Marcel M M, AU - Woodfine,Richard G, AU - Lyons,Timothy W, Y1 - 2013/10/29/ PY - 2013/10/31/entrez PY - 2013/10/31/pubmed PY - 2014/1/9/medline KW - carbonate-associated sulfur KW - geochemical modeling SP - 18407 EP - 12 JF - Proceedings of the National Academy of Sciences of the United States of America JO - Proc Natl Acad Sci U S A VL - 110 IS - 46 N2 - The Mesozoic Era is characterized by numerous oceanic anoxic events (OAEs) that are diagnostically expressed by widespread marine organic-carbon burial and coeval carbon-isotope excursions. Here we present coupled high-resolution carbon- and sulfur-isotope data from four European OAE 2 sections spanning the Cenomanian-Turonian boundary that show roughly parallel positive excursions. Significantly, however, the interval of peak magnitude for carbon isotopes precedes that of sulfur isotopes with an estimated offset of a few hundred thousand years. Based on geochemical box modeling of organic-carbon and pyrite burial, the sulfur-isotope excursion can be generated by transiently increasing the marine burial rate of pyrite precipitated under euxinic (i.e., anoxic and sulfidic) water-column conditions. To replicate the observed isotopic offset, the model requires that enhanced levels of organic-carbon and pyrite burial continued a few hundred thousand years after peak organic-carbon burial, but that their isotope records responded differently due to dramatically different residence times for dissolved inorganic carbon and sulfate in seawater. The significant inference is that euxinia persisted post-OAE, but with its global extent dwindling over this time period. The model further suggests that only ~5% of the global seafloor area was overlain by euxinic bottom waters during OAE 2. Although this figure is ~30× greater than the small euxinic fraction present today (~0.15%), the result challenges previous suggestions that one of the best-documented OAEs was defined by globally pervasive euxinic deep waters. Our results place important controls instead on local conditions and point to the difficulty in sustaining whole-ocean euxinia. SN - 1091-6490 UR - https://www.unboundmedicine.com/medline/citation/24170863/Sulfur_isotopes_track_the_global_extent_and_dynamics_of_euxinia_during_Cretaceous_Oceanic_Anoxic_Event_2_ L2 - http://www.pnas.org/cgi/pmidlookup?view=long&pmid=24170863 DB - PRIME DP - Unbound Medicine ER -