TRACKING THE INITIAL ONSET OF DEOXYGENATION ACROSS THE PALEOCENE-EOCENE THERMAL MAXIMUM

One of the most recent rapid and severe warming episodes occurred ~55.9 Ma at the end of the Paleocene. The mechanism(s) triggering the Paleocene-Eocene Thermal Maximum (PETM) remain debated but include: bolide impact and/or release of greenhouse gases via volcanoes, wildfires, or other marine and terrestrial carbon reservoirs. The sharp ~3‰ negative carbon isotope excursion defines the PETM and suggests a major perturbation to the global carbon cycle through the release of isotopically light carbon to the ocean-atmosphere system. In addition to warming, other environmental perturbations during this event include ocean acidification, permafrost loss, and a small increase in global euxinia (anoxic and sulfidic water column). There is limited evidence, however, for widespread deoxygenation or organic carbon burial, which contrasts the PETM with Mesozoic oceanic anoxic events. This research aims to better constrain the global spatiotemporal redox structure across the PETM global oceans using both novel and traditional geochemical tools.

Here, we will present new data obtained from an Arctic drill core (IODP Expedition 302, Site M0004). A suite of geochemical proxies will be used to constrain the local and global redox conditions during the PETM. Iron speciation and redox-sensitive trace metals (Mo, V, Mn, etc.) will provide important local redox constraints. A new proxy, thallium isotopes, will be used to reconstruct changes in global manganese oxide burial, which is directly related to the availability of marine oxygen. The combination of these redox proxies will provide a more complete picture of the spatiotemporal patterns of global redox variations for the PETM. The global PETM marine warming should cause initial deoxygenation due to gas solubility, with other feedbacks including increased organic carbon burial that could exacerbate oxygen loss. Understanding these feedbacks is vital for predicting future climate scenarios in the face of anthropogenic perturbation.