Novel Global Perspectives on Marine Redox Conditions During the Paleocene-Eocene Thermal Maximum

• Other Authors: Wadhams, Jane Alexandra (author)
• Format: Bachelor Thesis
• Language: English
• Published: 2020
• Subjects: Arctic; Arctic Ocean
• Online Access: http://purl.flvc.org/fsu/fd/FSU_libsubv1_scholarship_submission_1607696758_c012b1b2; https://diginole.lib.fsu.edu/islandora/object/fsu%3A759925/datastream/TN/view/%20Novel%20Global%20Perspectives%20on%20Marine%20Redox%20Conditions%20During%20the%20Paleocene-Eocene%20Thermal%20Maximum%20.jpg

Recent trends in marine deoxygenation resulting from the unprecedented modern release of carbon have raised concerns regarding the future of the global ocean’s redox structure. Past hyperthermal warming events are studied in order to make inferences on possible climate scenarios and of these events particularly the most extreme, the Paleocene-Eocene Thermal Maximum (PETM; ~56 Mya). The PETM is characterized by a large and rapid negative carbon isotope excursion caused by a sudden input of 4,500-10,000 of Pg of carbon into the Earth-atmosphere system. This study aimed to better constrain the timing of changes in marine redox during this critical event by applying a suite of geochemical proxies on samples from two localities (the Arctic Ocean and Atlantic Coastal Plain). FeT/Al, Mo, and V concentrations suggest that the Arctic experienced euxinia (anoxic and sulfidic water column) during the PETM, while the application of these proxies to the Atlantic section suggests the local depositional conditions were reducing but not completely euxinic. These local conditions are reducing enough to capture the global seawater signature. Each section records a positive shift in Tl isotopes at the onset of the carbon isotope excursion which tapered off during the carbon isotope excursion. These results suggest that oxygen quickly declined at the onset of climatic warming but steadily returned to oxic values as the hypothermal event terminated. The changes in redox during this event are likely a response to the massive warming and could provide a negative feedback to the associated perturbation of the global carbon cycle, providing a burial mechanism to the addition of carbon released over the event. Future work adding other proxies, such as Fe speciation, and higher resolution data could provide greater constraints to examine the plausibility of this idea.