Asynchronous δ¹³C_carb and δ¹³C_org records during the onset of the Mulde (Silurian) positive carbon isotope excursion from the Altajme core, Gotland, Sweden

High-resolution paired analyses of δ¹³C_carb and δ¹³C_org from a new drill core from Gotland, Sweden, demonstrate asynchronous positive change in the carbon isotope records during the onset of one of the major Silurian biogeochemical events known as the Mulde Event or “Big Crisis”. The detailed carbon isotope record presented here provides Δ¹³C (the difference between δ¹³C_carb and δ¹³C_org) and allows the calculation of changes in organic carbon burial (f_org) throughout the late Wenlock. The paired data suggest a ~ 38% increase in f_org during the peak of the positive δ¹³C_carb excursion and the high-resolution record reveals several short-lived inflections in Δ¹³C that have not been previously identified. When combined with sedimentological and sequence stratigraphic data from multiple paleocontinents, the new data presented here provide strong evidence for a transient global decrease in CO₂, in support of previous interpretations of regression and global cooling coinciding with the Mulde Extinction Event.