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Late Ordovician mass extinction caused by volcanism, warming, and anoxia, not cooling and glaciation

Bond, David P.G.; Grasby, Stephen E.

Authors

Stephen E. Grasby



Abstract

The Ordovician saw major diversification in marine life abruptly terminated by the Late Ordovician mass extinction (LOME). Around 85% of species were eliminated in two pulses 1 m.y. apart. The first pulse, in the basal Hirnantian, has been linked to cooling and Gondwanan glaciation. The second pulse, later in the Hirnantian, is attributed to warming and anoxia. Previously reported mercury (Hg) spikes in Nevada (USA), South China, and Poland implicate an unknown large igneous province (LIP) in the crisis, but the timing of Hg loading has led to different interpretations of the LIP-extinction scenario in which volcanism causes cooling, warming, or both. We report close correspondence between Hg, Mo, and U anomalies, declines in enrichment factors of productivity proxies, and the two LOME pulses at the Ordovician-Silurian boundary stratotype (Dob's Linn, Scotland). These support an extinction scenario in which volcanogenic greenhouse gases caused warming around the Katian-Hirnantian boundary that led to expansion of a preexisting deepwater oxygen minimum zone, productivity collapse, and the first LOME pulse. Renewed volcanism in the Hirnantian stimulated further warming and anoxia and the second LOME pulse. Rather than being the odd-one-out of the "Big Five" extinctions with origins in cooling, the LOME is similar to the others in being caused by volcanism, warming, and anoxia.

Citation

Bond, D. P., & Grasby, S. E. (2020). Late Ordovician mass extinction caused by volcanism, warming, and anoxia, not cooling and glaciation. Geology, 48(8), 777-781. https://doi.org/10.1130/G47377.1

Journal Article Type Article
Acceptance Date Mar 22, 2020
Online Publication Date May 18, 2020
Publication Date Aug 1, 2020
Deposit Date Mar 23, 2020
Publicly Available Date May 19, 2021
Journal Geology
Print ISSN 0091-7613
Electronic ISSN 1943-2682
Publisher Geological Society of America
Peer Reviewed Peer Reviewed
Volume 48
Issue 8
Pages 777-781
DOI https://doi.org/10.1130/G47377.1
Public URL https://hull-repository.worktribe.com/output/3480749
Publisher URL https://pubs.geoscienceworld.org/gsa/geology/article/48/8/777/586486/Late-Ordovician-mass-extinction-caused-by

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Dobs Linn Fig 1 R1 (354 Kb)
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Dobs Linn Fig 2 (1.1 Mb)
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Dobs Linn Fig 3 (1.5 Mb)
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Dobs Linn Fig 4 (491 Kb)
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Bond And Grasby DR1 (49 Kb)
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