Mercury enrichments provide evidence of Early Triassic volcanism following the end-Permian mass extinction

Abstract Oceanic environments and biotas were in a state of near-continuous perturbation during the Early Triassic, the ~5-million-year interval following the latest Permian mass extinction (LPME), but the underlying cause(s) remain uncertain. The role of episodic volcanic or intrusive magmatic activity in triggering global-scale perturbations during this interval is suspected but has not been strongly evidenced to date. Here, we investigate the record of volcanism through the Early Triassic (with a focus on the Smithian-Spathian Boundary, or SSB) using mercury (Hg) concentrations in marine sediments as a proxy. This study examines five marine sections from three paleo-oceans (Paleo-Tethys, Neo-Tethys, and Panthalassa) representing a range of depositional settings from shallow platform to deep slope. Our results suggest that volcanic and magmatic activity of the Siberian Traps Large Igneous Province (STLIP) was most intense during the first ~1.3 million years following the LPME, and that termination of its most active stage was responsible for a sharp cooling event at the SSB. Variations in the intensity of STLIP activity are thus likely to account for the large (>8‰) fluctuations of δ 13 C carb and related changes in oceanic redox and environmental conditions that characterized the Griesbachian to Smithian substages of the Early Triassic in marine sections globally. We hypothesize that a strong reduction or cessation of STLIP activity at the SSB set the stage for the recovery of marine biodiversity and ecosystems in the Spathian and later.