An integrated biomarker, isotopic and palaeoenvironmental study through the Late Permian event at Lusitaniadalen, Spitsbergen

The largest extinction of the Phanerozoic occurred near the Permian/Triassic (P/Tr) boundary some 252 Ma ago. Several scenarios and drivers have been proposed for this event. Here we report for the first time an integrated study comprising sedimentological data, biomarker distributions/abundances and selected stable carbon and hydrogen isotopes along with bulk isotopes (δ³⁴S_pyrite, δ¹³C_carb, δ¹³C_org) for a Late Permian section from Lusitaniadalen, Spitsbergen, Norway. Sedimentological and geochemical data support a marine transgression and collapse of the marine ecosystem in the Late Permian. Strong evidence for waxing and waning of photic zone euxinia throughout the Late Permian is provided by Chlorobiaceae-derived biomarkers (including δ¹³C data) and δ³⁴S_pyrite, implying multiple phases of H₂S outgassing and potentially several pulses of extinction. A rapid decrease in abundance of various land-plant biomarkers prior to the marine collapse event indicates a dramatic decline of land-plants during the Late Permian and/or increasing distance from palaeoshoreline as a consequence of sea level rise. Changes in δD of selected biomarkers also suggest a change in source of organic matter (OM) or sea level rise. We also found biomarker and isotopic evidence for a phytoplanktonic bloom triggered by eutrophication as a consequence of the marine collapse. Compound specific isotope analyses (CSIA) of algal and land-plant-derived biomarkers, as well as δ¹³C of carbonate and bulk OM provide strong evidence for synchronous changes in δ¹³C of marine and atmospheric CO₂, attributed to a ¹³C-depleted source. The source could be associated with isotopically depleted methane released from the melting of gas clathrates and/or from respired OM, due to collapse of the marine ecosystem.