Geochemical records reveal protracted and differential marine redox change associated with Late Ordovician climate and mass extinctions

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dc.contributor.authorKozik, Nevinen
dc.contributor.authorGill, Benjamin C.en
dc.contributor.authorOwens, Jeremy D.en
dc.contributor.authorLyons, Timothy W.en
dc.contributor.authorYoung, Seth A.en
dc.date.accessioned2022-01-13T04:04:45Zen
dc.date.available2022-01-13T04:04:45Zen
dc.date.issued2022-01-10en
dc.date.updated2022-01-13T04:04:41Zen
dc.description.abstractThe Ordovician (Hirnantian; 445 Ma) hosts the second most severe mass extinction in Earth history, coinciding with Gondwanan glaciation and increased geochemical evidence for marine anoxia. It remains unclear whether cooling, expanded oxygen deficiency, or a combination drove the Late Ordovician Mass Extinction (LOME). Here, we present combined iodine and sulfur isotope geochemical data from three globally distributed carbonate successions to constrain changes in local and global marine redox conditions. Iodine records suggest locally anoxic conditions were potentially pervasive on shallow carbonate shelves, while sulfur isotopes suggest a reduction in global euxinic (anoxic and sulfidic) conditions. Late Katian sulfate-sulfur isotope data show a large negative excursion that initiated during elevated sea level and continued through peak Hirnantian glaciation. Geochemical box modeling suggests a combination of decreasing pyrite burial and increasing weathering are required to drive the observed negative excursion suggesting a ∼3% decrease of global seafloor euxinia during the Late Ordovician. The sulfur datasets provide further evidence that this trend was followed by increases in euxinia which coincided with eustatic sea-level rise during subsequent deglaciation in the late Hirnantian. A persistence of shelf anoxia against a backdrop of waning then waxing global euxinia was linked to the two LOME pulses. These results place important constraints on local and global marine redox conditions throughout the Late Ordovician and suggest that non-sulfidic shelfal anoxia— along with glacioeustatic sea level and climatic cooling—were important environmental stressors that worsened conditions for marine fauna, resulting in the second-largest mass extinction in Earth history and the only example during an icehouse climate.en
dc.description.versionPublished versionen
dc.format.mimetypeapplication/pdfen
dc.identifiere2021AV000563 (Article number)en
dc.identifier.doihttps://doi.org/10.1029/2021AV000563en
dc.identifier.orcidGill, Benjamin [0000-0001-7402-0811]en
dc.identifier.urihttp://hdl.handle.net/10919/107584en
dc.identifier.volume3en
dc.language.isoenen
dc.rightsCreative Commons Attribution-NonCommercial 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by-nc/4.0/en
dc.titleGeochemical records reveal protracted and differential marine redox change associated with Late Ordovician climate and mass extinctionsen
dc.title.serialAGU Advancesen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.otherArticleen
pubs.organisational-group/Virginia Techen
pubs.organisational-group/Virginia Tech/Scienceen
pubs.organisational-group/Virginia Tech/Science/Geosciencesen
pubs.organisational-group/Virginia Tech/All T&R Facultyen
pubs.organisational-group/Virginia Tech/Science/COS T&R Facultyen

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