TEMPERATURE-DRIVEN NUTRIENT RECYCLING CONTROLLED THE GLOBAL REDOX LANDSCAPE DURING THE END-PERMIAN MASS EXTINCTION (Invited Presentation)

The Mesozoic, which contains three of the “Big Five” mass extinctions as well as multiple Oceanic Anoxic Events (OAEs), presents a series of exemplary windows into the role of warming temperatures on marine biogeochemical cycles and marine biodiversity. The most notable example is the extreme warming at the Paleozoic-Mesozoic boundary that induced the largest metazoan mass extinction of the Phanerozoic—the end-Permian mass extinction. Although a close relationship with Siberian Traps volcanism has long been recognized, a causal mechanism for the extinction that is consistent with various proxy records of geochemical conditions through the interval has yet to be determined. To identify this causal mechanism, we combine Earth system modeling with a compilation of published global and local redox interpretations from the end-Permian. Our cGENIE results show that a temperature-driven increase in microbial respiration can reconcile reconstructions of the spatial distribution of euxinia and seafloor anoxia spanning the Permian/Triassic transition. We illustrate how a dynamic biological pump, characterized by enhanced metabolic rates, would have strengthened upper-ocean nutrient (phosphate) recycling, and thus shoaled and intensified the oxygen minimum zones, eventually causing euxinic waters to expand onto continental shelves and poison benthic habitats. Taken together, our findings demonstrate the sensitive interconnections between temperature, microbial metabolism, ocean redox state, carbon cycling, and shallow-marine carbon isotope values with mass extinction. These connections may have unique implications for other carbon cycle and climate perturbations through the Mesozoic and Earth history.