EXPANSION OF REDUCING MARINE ENVIRONMENTS DURING THE EARLY SILURIAN IREVIKEN BIOGEOCHEMICAL EVENT

New sulfur isotope data, including δ³⁴S_py (pyrite) and δ³⁴S_CAS (carbonate-associated sulfate), provide additional evidence for the expansion of reducing oceanic conditions during the early Silurian Ireviken Biogeochemical Event (IBE). This event consists of major perturbations to biogeochemical cycles including major positive carbon and sulfur isotope excursions and increased biotic turnover/extinction. In addition, recent studies have hypothesized that this event coincides with an expansion of reducing marine conditions which allowed for organic carbon burial rates to increase globally leading to the Ireviken positive Carbon Isotope Excursion (ICIE).

Recent work in the Altajme core from Gotland, Sweden provides the highest resolution carbon isotopic record of the ICIE in a stratigraphic section and provides an expanded stratigraphic section ideal for studying biogeochemical events. Within the Altajme core, the δ³⁴S_py values and pyrite concentrations increase at the onset of the ICIE indicating an increase in pyrite burial rates in the marine sediments locally. This dataset along with other previously published δ³⁴S_CAS datasets from the Baltic and distant basins suggests an expansion of reducing conditions led to an increase in organic carbon burial and the ICIE.