Water mass denitrification during the latest Permian extinction in the Sverdrup Basin, Arctic Canada

Abstract

Late Permian–Early Triassic bulk sedimentary nitrogen isotope (δ¹⁵N) and biomarker data have been generated from the northwest margin of Pangea. Sediments from the Buchanan Lake section, Arctic Canada, deposited prior to the latest Permian extinction (LPE) event are characterized by positive δ¹⁵N values of ~9‰ associated with the presence of lycopane, implying upwelling of denitrified waters from an expanded oxygen minimum zone. The data show that anoxic bottom-water conditions were not developed in northeastern Panthalassa during the Late Permian. Promoted by dispersing coal ash from Siberian Traps volcanics, as marked by an abrupt rise in C/N ratios (>20) prior to the LPE event, euxinic conditions first developed at the LPE. Pronounced differences in the nitrogen inventory across the LPE event, however, suggest that while unfavorable conditions prevailed for aerobiosis in the paleo-Tethys, persistent upwelling of deoxygenated (denitrified) waters occurred in the Sverdrup Basin across the LPE, excluding the prevalence of photic zone euxinia along the northwest margin of Pangea.