INSIGHTS INTO THE MECHANISMS OF END-TRIASSIC MASS EXTINCTION AND ENVIRONMENTAL CHANGE: AN INTEGRATED PALEONTOLOGIC, BIOMARKER AND ISOTOPIC APPROACH

The end-Triassic mass extinction (ETE; ~201.4 million years ago) decimated biodiversity in Earth’s marine and terrestrial realm. The ETE has been linked to one of the most areally extensive large igneous provinces, the Central Atlantic Magmatic Province (CAMP), through rapid CO₂–driven global warming, changes in ocean circulation, and ocean acidification and deoxygenation. Deoxygenation of ocean waters can alter nutrient inventories and lead to the shoaling of toxic hydrogen sulfide into the photic zone (hence photic zone euxinia, PZE), thus leading to turnovers in eukaryotic and prokaryotic phytoplankton suited to ammonium assimilation or nitrogen fixation, such as observed during the end-Permian mass extinction. However, current evidence for such conditions across the ETE derives only from marginal marine basins of the Tethys and Central Atlantic realms (e.g., the canonical St. Audrie's Bay section), and do not provide a reliable picture of environmental change in the open ocean. A new ~3 million year long record from Haida Gwaii (formerly Queen Charlotte Islands), British Columbia, Canada, provides the first conclusive evidence of PZE and disrupted biogeochemistry in open ocean waters of the northeastern Panthalassic Ocean at the time of the ETE. The development of PZE was paralleled by a perturbed nitrogen cycle, ecological turnovers among non-calcifying groups including eukaryotic algae relying on reduced forms of nitrogen, and enhanced cyanobacterial biomass and methane oxidation, raising the possibility of a potent global extinction mechanism.