98-3 Ireviken (Silurian) Oceanic Anoxic Event was Initiated by A Green Tide

Session: Linking Biodiversity Loss to Environmental Stressors Through Integrated Approaches

Presenting Author:

Bradley Cramer

Authors:

Marshall, Nathan¹, Love, Gordon Davidson², Cramer, Bradley Douglas³, Hartke, Emma Ruth⁴, Calner, Mikael⁵, Oborny, Stephan C.⁶, Bancroft, Alyssa⁷

(1) UC - Riverside, Riverside, CA, USA, (2) UC Riverside, Earth and Planetary Sciences, Riverside, CA, USA, (3) University of Iowa Earth & Environmental Sciences, Iowa City, IA, USA, (4) Penn State University, State College, PA, USA, (5) Lund University, Lund, Sweden, (6) Kansas Geological Survey, Lawrence, KS, USA, (7) Iowa Geological Survey - University of Iowa, Iowa City, Iowa, USA,

Abstract:

The Ireviken Biogeochemical Event was a Silurian Oceanic Anoxic Event that dramatically altered major- and trace-element nutrient cycling in the oceans and led to a biotic crisis known as the Ireviken Extinction Event. This event, first identified in the fossil record of conodonts, is also identified by a major perturbation to the global carbon cycle with carbonate carbon isotope values reaching +6 per mil in some locations. Whereas this event has been identified in more than two dozen locations around the globe, and is the most well-studied Silurian biogeochemical event, the precise cause(s) of the event initiation remain enigmatic.

 

Here, we present new records of nitrogen isotopes and lipid biomarkers from across the Ireviken Biogeochemical Event from samples from the Altajme Drill Core. The Altajme Core was drilled in Gotland, Sweden, and now is the most highly resolved record of any Paleozoic biogeochemical event. The lipid biomarker data demonstrate that a bloom of green algae coincided with the onset of the Ireviken Biogeochemical Event and began just prior to the expansion of reducing environments during the earliest part of the Sheinwoodian Epoch. The nitrogen isotope data support the lipid data and demonstrate a crash in nitrogen isotope values during the green algal bloom, which most likely represents a decrease in bioavailable nitrogen created by excess productivity. This sequence of events in the data demonstrate that the Ireviken Biogeochemical Event was a productivity-driven ‘green-tide event’ in the Silurian.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10627

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