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Sylvain Richoz

Sylvain Richoz

Senior lecturer

Sylvain Richoz

“Hypoxic” Silurian oceans suggest early animals thrived in a low-O2 world

Author

  • Emma R. Haxen
  • Niels H. Schovsbo
  • Arne T. Nielsen
  • Sylvain Richoz
  • David K. Loydell
  • Nicole R. Posth
  • Donald E. Canfield
  • Emma U. Hammarlund

Summary, in English

Atmospheric oxygen (O2) concentrations likely remained below modern levels until the Silurian–Devonian, as indicated by several recent studies. Yet, the background redox state of early Paleozoic oceans remains poorly constrained, hampering our understanding of the relationship between early animal evolution and O2. Here, we present a multi-proxy analysis of redox conditions in the Caledonian foreland basin to Baltica from the early to the mid-Silurian. Our results indicate that anoxic to severely hypoxic bottom waters dominated during deposition of the Silurian sediments cored in the Sommerodde-1 well (Bornholm, Denmark), and regional comparison suggests that these conditions persisted across the Baltoscandian foreland basin. Indeed, even during times of relative oxygenation, ichnological observations indicate that conditions were, at most, very weakly oxic. The results suggest that dissolved O2 was generally scarce in the bottom waters of the extensive Silurian seaway between Baltica and Avalonia, even between Paleozoic “Anoxic Events”. In light of delayed oxygenation of the atmosphere–hydrosphere system, it may be time to consider that early animals were adapted to “hypoxia” and thrived through ∼100 million years of low-O2 conditions after the Cambrian.

Department/s

  • Molecular Evolution
  • Lithosphere and Biosphere Science
  • StemTherapy: National Initiative on Stem Cells for Regenerative Therapy
  • EpiHealth: Epidemiology for Health
  • LUCC: Lund University Cancer Centre

Publishing year

2023-11-15

Language

English

Publication/Series

Earth and Planetary Science Letters

Volume

622

Document type

Journal article

Publisher

Elsevier

Topic

  • Geology

Keywords

  • animal evolution
  • Baltic basin
  • caledonian foreland basin
  • ocean oxygenation
  • redox
  • Silurian

Status

Published

Research group

  • Molecular Evolution

ISBN/ISSN/Other

  • ISSN: 0012-821X