THE CENOMANIAN – TURONIAN OCEANIC ANOXIC EVENT 2: NEW INSIGHTS FROM THE TROPICAL AMERICAS

Date

2020-12

Journal Title

Journal ISSN

Volume Title

Publisher

Abstract

The Cretaceous Period is characterized by punctuated episodes of high atmospheric CO2 concentra- tions, global warming, ocean acidification and ocean deoxygenation. These episodes, known as ocean- ic anoxic events –OAEs–are among the most-studied episodes of marine environmental perturbation given the apparent synchronous occurrence of organic-rich sediments in a wide range of marine envi- ronments. One of the most extensive anoxic events and focus of this research is the Cenomanian- Turonian OAE2. Many studies have focused on the onset of the event, concluding that the magmatism associated to the Caribbean Large Igneous Province (CLIP) triggered a cascade of adverse environ- mental conditions that change the chemistry of the water at this time, leading to ocean deoxygenation and deposition of organic-rich rocks. In this research, I first tested the hypothesis that the initiation of ocean anoxia was triggered by CLIP magmatism. My results show a temporal discrepancy of at least 5 million years between CLIP magmatism and OAE2 initiation, challenging the idea that OAE2 was triggered by the eruption of the oceanic plateau and a need for another mechanism to explain the onset of anoxia 94 Ma. A second hypothesis tested in this research was the supposed link between ocean anoxia and marine extinction. My findings suggest that there was no mass extinction during OAE2 and more importantly that the euxinic area despite being 20 times higher than the present day was not as widespread as during other events of mass extinction. Finally, the role of epicontinental seas in carbon cycling during OAE2 was examined using a high-resolution study from two sections in Colombia. My results suggest that despite constituting an important element of the ocean during OAE2, the amount of organic carbon buried was negligible compared to marginal areas under the influence of upwelling.

Description

Keywords

Anoxia, extinction, organic matter, OAE2, Colombia

Citation