Linking the progressive expansion of reducing conditions to a stepwise mass extinction event in the late Silurian oceans

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The late Ludlow Lau Event was a severe biotic crisis in the Silurian, characterized by resurgent microbial facies and faunal turnover rates otherwise only documented during the "big five" mass extinctions. This asynchronous late Silurian marine extinction event preceded an associated positive carbon isotope excursion (CIE), the Lau CIE, although a mechanism for this temporal offset remains poorly constrained. Here, we report thallium isotope data from locally reducing late Ludlow strata within the Baltic Basin to document the earliest onset of global marine deoxygenation. The initial expansion of anoxia coincided with the onset of the extinction and therefore preceded the Lau CIE. Additionally, sulfur isotope data record a large positive excursion parallel to the Lau CIE, interpreted to indicate an increase in pyrite burial associated with the widely documented CIE. This suggests a possible global expansion of euxinia (anoxic and sulfidic water column) following deoxygenation. These data are the most direct proxy evidence of paleoredox conditions linking the known extinction to the Lau CIE through the progressive expansion of anoxia, and most likely euxinia, across portions of the late Silurian oceans.


  • Chelsie N. Bowman
  • Seth A. Young
  • Dimitri Kaljo
  • Mats E. Eriksson
  • Theodore R. Them
  • Olle Hints
  • Tõnu Martma
  • Jeremy D. Owens
External organisations
  • National High Magnetic Field Laboratory
  • Tallinn University of Technology
  • Florida State University
  • College of Charleston
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Geology
Original languageEnglish
Pages (from-to)968-972
Number of pages5
Issue number10
Publication statusPublished - 2019
Publication categoryResearch

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