Silurian carbon cycle perturbations — global and local drivers, their preservation, and links to astronomical forcing

The Silurian is characterised by a highly volatile carbon cycle, exemplified through high-magnitude positive carbon isotope excursions (CIEs). The largest and best-known CIEs are the Early Sheinwoodian/Ireviken, Homerian/Mulde, and Mid-Ludfordian/Lau, reaching magnitudes of up to +11‰. While ocean circulation is often inferred as a controlling factor, questions remain concerning their exact driving mechanisms. Yet, significant advances have been made recently, particularly in the context of redox cycling and astronomical forcing. Here, we present a review of Silurian CIEs, with a special focus on cyclostratigraphy, and examine how their expression and preservation in the rock record have influenced our understanding. Emerging evidence suggests astronomical forcing may have influenced several CIEs. Specifically, carbon burial appears to have been paced by eccentricity during some CIEs. This insight is a major step forward in the disentanglement of Silurian carbon cycle dynamics and simultaneously a contribution to the ongoing refinement of the Silurian time scale. Still, the climatic pathways associated with astronomical forcing remain ambiguous and require continued cyclostratigraphic investigation. Future cyclostratigraphic work should focus on the extraction of astronomical cycles from globally distributed sites across a range of depositional environments, accounting for palaeogeographical idiosyncrasies, to separate global from local, and primary from diagenetic signals.