• Sulphur and carbon isotopes as tracers of past sub-seafloor microbial activity

    • Patrick Meister
      Department of Geodynamics and Sedimentology, Faculty of Earth Sciences, Geography and Astronomy, University of Vienna
    • Benjamin Brunner
      Department of Geological Sciences, University of Texas at El Paso (UTEP)
    • Aude Picard
      School of Life Sciences, University of Nevada, Las Vegas
    • Michael E. Böttcher
      Geochemistry & Isotope Biogeochemistry Group, Leibniz-Institute for Baltic Sea Research (IOW)
    • Bo Barker Jørgensen
      Center for Geomicrobiology, Aarhus University
  • Microbial life below the seafloor has changed over geological time, but these changes are often not obvious, as they are not recorded in the sediment. Sulphur (S) isotope values in pyrite extracted from a Plio- to Holocene sequence of the Peru Margin (Ocean Drilling Program, ODP, Site 1229) show a down-core pattern that correlates with the pattern of carbon (C) isotopes in diagenetic dolomite. Early formation of the pyrite is indicated by the mineralogical composition of iron, showing a high degree of pyritization throughout the sedimentary sequence. Hence, the S-record could not have been substantially overprinted by later pyrite formation. The S- and C-isotope profiles show, thus, evidence for two episodes of enhanced microbial methane production with a very shallow sulphate-methane transition zone. The events of high activity are correlated with zones of elevated organic C content in the stratigraphic sequence. Our results demonstrate how isotopic signatures preserved in diagenetic mineral phases provide information on changes of past biogeochemical activity in a dynamic sub-seafloor biosphere.

  • PDF

  • http://phaidra.univie.ac.at/o:931173

  • Article

  • Published Version

  • Scientific Reports

  • 2019

  • 9

  • Springer Nature

  • English

  • Open access

  • CC BY Attribution 4.0 International
    © The Author(s) 2019

  • MRTN-CT-2006-035868 – European Union (all programmes)

  • 2045-2322

  • Element cycles; Marine chemistry