Carbonate geochemistry via ICP-MS of the Ireviken Biogeochemical Event from the Altajme core, Gotland, Sweden

The Ireviken Biogeochemical Event (IBE) represents a major perturbation to the global carbon cycle during the Silurian, characterized by a negative 1δ3Corg excursion paired with rising δ13Ccarb values. The IBE is accompanied by various extinction events. New whole-rock digestion data reveal depletion of redox sensitive elements coincident with the Ireviken positive carbon isotope excursion. Both of these suggest an expansion of reducing conditions during the event. Heavy metal concentrations peak at the onset of the IBE and correspond with the onset of the extinction, supporting the case for heavy metal poisoning causing extinction. New selective carbonate digestion data reveals anomalies with redox sensitive metals prior to the Ireviken, coincident with a short, yet significant, positive excursion in δ18Ocarb. Enrichment of these redox sensitive elements during the δ18Ocarb excursion provides evidence that a brief cooling event took place, which we have named the Altajme Cooling Event. The use of partial carbonate digestion data for the Ireviken has proved a useful tool for reconstructing marine settings and validates the methodology for Paleozoic biogeochemical events.