Paleogene polar plankton and paleoproductivity: new proxy data from the Eocene – Oligocene transition

Polar plankton plays a large role in global carbon cycling. There is a significant lack of knowledge of these biotas, however. The main goal of our project is to understand how plankton and oceans interacted in the past during the Eocene/Oligocene (E/O) transition, when significant climate shifts happened. We use a multiproxy approach by combining microfossils and geochemical data. Our study includes the first-ever comprehensive surveys of both diatom and radiolarian plankton diversity (siliceous protists dominating the preserved microfossil record in polar regions). We analyze abundance, diversity, speciation, and extinction rates between 40 and 30 Ma. This plankton data, correlated togeochemical and sedimentological proxies of ocean conditions and carbon pump activity, geographic water masses, and nutrient export data will contribute to global syntheses to determine the global significance and role of plankton in climate change at the E/O transition. Our data comes from several deep-sea drilling Sites from the Atlantic and the Indian Ocean sectors of the Southern Ocean: 689, Weddell Sea; 511 and 1090, near the Atlantic sector polar front; and Indian sector 748, Kerguelen Plateau. Our results show a latitudinally differentiated pattern of paleoceanographic and productivity change. Episodes of increased Southern Ocean productivity occurred well prior to the E/O boundary within the late Eocene, beginning at ca 36-37 Ma. Diversity of siliceous plankton increased with productivity, and shows major episodes of evolutionary turnoverin the late Eocene and at the E/O boundary correlated to productivity and temperature change.