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Biological productivity in the Southern Ocean across the Eocene-Oligocene transition

The Eocene-Oligocene transition (EOT, ~34Ma) marks a dramatic climate change and carbon cycle perturbation in the Cenozoic. Understanding the variations in export productivity associated with EOT provides important information about the feedback in regulating climate. We use the new generated benthic and planktonic oxygen and carbon isotope records combined with paleoproductivity proxies - Biological Barium [bio-Ba MAR] and benthic foraminifera accumulation rates [BFAR] - to infer variations in productivity during the EOT period in relation to changes in climate and paleoceanography. In addition, we present preliminary diatom diversity data. Marine diatoms have been known to be great contributors to the biological ocean carbon pump, so these data provide support for the understanding of these climatic events. Samples are from the Atlantic (ODP 689 and 1090) and Indian (ODP 748) sectors of the Southern Ocean. Our multiproxy records show evidence of increased export productivity in different periods throughout the Southern Ocean across EOT. The increase in productivity revealed in the late Eocene (~37 Ma) corroborates with an increase in marine diatoms diversity, suggesting that it could have contributed to the decrease in atmospheric CO2 and consequently to the cooling state. The timing of some observed changes differs in the sites of the Atlantic sector of the Southern Ocean. The increase in productivity in the early Oligocene in the farther to the south ODP 689 site may be related to the water mass changes and development of the Atlantic Circumpolar Current.


Gabrielle Rodrigues de Faria1,2, Volkan Özen1,2, David Lazarus1, Ulrich Struck1,2, Johan Renaudie1, Gayane Asatryan1
1Museum für Naturkunde, Germany; 2Department of Earth Sciences, Freie Universität, Germany
GeoKarlsruhe 2021