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Expansion of Reducing Marine Environments During the Ireviken Biogeochemical Event: Evidence From the Altajme Core, Gotland, Sweden
Journal article   Open access   Peer reviewed

Expansion of Reducing Marine Environments During the Ireviken Biogeochemical Event: Evidence From the Altajme Core, Gotland, Sweden

Brittany M. Stolfus, Lindsi J. Allman, Seth A. Young, Mikael Calner, Emma R. Hartke, Stephan C. Oborny, Alyssa M Bancroft and Bradley D Cramer
Paleoceanography and paleoclimatology, Vol.38(2), e2022PA004484
02/2023
DOI: 10.1029/2022PA004484
Appears in  UI Libraries Support Open Access
url
https://doi.org/10.1029/2022PA004484View
Published (Version of record) Open Access

Abstract

New δ34Spy (pyrite) and δ34SCAS (carbonate‐associated sulfate) across the Llandovery‐Wenlock boundary (∼432 Ma) provide evidence for the expansion of reduced marine environments during the Ireviken Biogeochemical Event. This event consists of a major positive carbon isotope excursion, increased biotic turnover, and other major perturbations and changes within biogeochemical cycles. This interval of time has been hypothesized to coincide with an expansion of reducing marine environments that caused increased organic carbon burial and led to the Ireviken positive carbon isotope excursion (ICIE). Previous high‐resolution carbon isotope work in the Altajme core from Gotland, Sweden provides the highest resolution record of the ICIE yet documented and provides an ideal expanded stratigraphic section to study this event. Local expansion of reduced marine environments within the deeper shelf setting of the Altajme core is indicated by a positive shift in δ34Spy values and increase in pyrite sulfur concentrations at the onset of the ICIE. These data are indicative of increased microbial sulfate reduction within this portion of the Baltic Basin. Combined with new δ34SCAS data from this core, as well as additional data from distant basins, the new data presented here suggest a global expansion of reduced environments led to an increase in organic carbon burial and the ICIE. Plain Language Summary New sulfur isotope data from the Silurian Period (∼432 Myr ago) provide evidence of low‐oxygen marine environments during a major extinction event and global carbon cycle perturbation known as the Ireviken Biogeochemical Event (IBE). The high‐resolution data presented here build upon recent data generated from a ∼300 m long drill core recovered from the Swedish island of Gotland that records this important ancient global change event in one of the thickest and most complete stratigraphic sections available anywhere in the world. Our new high‐resolution record, combined with data from other areas across the globe, demonstrate that there was likely a global expansion of low‐oxygen environments in the oceans at the very onset of this biogeochemical event that played an important role in both the extinction event as well as the global carbon cycle perturbation. Key Points New high‐resolution sulfur isotope data show the expansion of reducing environments during the onset of the Ireviken Biogeochemical Event Reducing environment expansion began prior to the onset of Ireviken positive carbon isotope excursion Compilation of data from Laurentia and Baltica suggest this may have been a global redox event
 Sweden Gotland Ireviken sulfur UIOWA OA Agreement

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