Volcanic proxies from the northern Pangean margin across the Permian-Triassic boundary: Evidence of intermittent Siberian Traps activity

The End Permian Mass Extinction (EPME) occurred at 251.9 Ma and is the largest extinction event in the Phanerozoic. More than 80% of marine species and ~75% of terrestrial species were wiped out in <100 kyr. The event is marked by a negative carbon isotope excursion (CIE) that has a rapid onset and sustained duration, indicating the release of huge volumes of isotopically light carbon to the ocean-atmosphere system. The scientific consensus is that the carbon cycle disturbances were caused by the emplacement of the Siberian Traps large igneous province (LIP), likely from a combination of magmatic degassing and contact metamorphism in the organic carbon- and evaporite-rich Tunguska Basin. However, the timing and tempo of the Siberian Traps emplacement relative to the environmental disturbances can be better constrained. We investigated four shallow localities from Svalbard and the Barents Sea, which during the Permian-Triassic interval were part of a semi-enclosed epicontinental sea on the northern margin of Pangaea. We use osmium isotopes (¹⁸⁸Os/¹⁸⁷Os) and mercury (Hg) enrichments to identify when the Siberian Traps were most active with respect to carbon cycle disturbances (δ¹³C_org) through these four shallow marine archives. Our results indicate a strong volcanic signature coincident with the main negative CIE, with fluctuating signals through the body of the CIE itself that are indicative of pulsed Siberian Traps activity. Osmium isotopes show considerable variations through the Permian-Triassic boundary, suggesting that the enclosed nature of the seaway preserved rapid seawater chemistry changes in response to changing climatic and volcanic conditions. These far-field results can be directly tied to biomarker and radiometric age estimates of the EPME to improve the relative and absolute chronologies of the extinction event and the elevated magmatic activity.