Impacts of volcanism on geochemical records during the Late Permian-Early Triassic transition in northern and middle Norwegian continental margins

Abstract

The end-Permian mass extinction (EPME; ∼252 Ma), known as the largest extinction event during the Phanerozoic Eon, provides a critical case study to understand the impacts of anthropogenic climate change. The warming associated with the EPME was likely triggered by the emissions of large quantities of CO₂ during the eruption of the voluminous Siberian Traps (ST) volcanism, which eliminated 80 to 90 % of marine species and 70 % of terrestrial species. However, the links between volcanism, negative carbon isotope excursions (nCIEs), chemical weathering, oceanic anoxia, and biotic turnover remain poorly understood. To better understand these connections, we analyze organic carbon isotopes, major element, and trace element geochemistry from two shallow marine sites at the Finnmark and Trøndelag Platforms in Norway, which serve as proxies for tracing volcanic-induced biogeochemical perturbations. Enhanced chemical weathering across the PTB at the Finnmark Platform and during the earliest Triassic at the Trøndelag Platform is indicated by increases in chemical weathering proxies (CIA, CIW, PIA, and Rb/Sr ratios) and decreases in WIP, along with indirect support from Li enrichment. At the Finnmark Platform, transient enrichments in primary productivity-sensitive elements (P and Ni) precede the PTB, but these signals likely result from a combination of nutrient input and localized lithological controls rather than a direct increase in marine productivity. This phase coincides with a brief period of reduced oxygen availability, as indicated by elevated U_EF, V_EF, and U/Th ratios, followed by a return to more oxygenated conditions. In contrast, at the Trøndelag Platform, sustained enrichment of P_EF, Ni_EF, U_EF, and U/Th ratios during the earliest Triassic suggests episodic oxygen depletion was likely driven by sediment redeposition processes rather than persistent euxinia or continuous biological productivity. The contrasting geochemical responses observed at the two platforms highlight the complexity of regional environmental feedbacks during the EPME, highlighting the importance of integrating multiple geochemical proxies in tracking environmental responses to climate change.