Tuesday, 28 August 2007 - 2:50 PM
2.P1.A-5
Abrupt turnover in calcareous-nannoplankton assemblages across the Paleocene/Eocene Thermal Maximum: implications for surface-water oligotrophy over the Kerguelen Plateau, Southern Indian Ocean
Shijun Jiang and Sherwood Wise Jr. Geological Sciences, Florida State University, 108 Carraway Building, Tallahassee, FL 32306-4100
Ocean Drilling Program (ODP) Core 183-1135A-25R-4 from the Kerguelen Plateau in the Southern Ocean represents only the second complete, expanded section of the Paleocene/Eocene Thermal Maximum (PETM; ~55 Ma) recovered from Antarctic waters. Calcareous nannoplankton underwent an abrupt turnover across the PETM. Although Chiasmolithus, Discoaster, and Fasciculithus exponentially increase in abundance at the onset, the former abruptly drops but then rapidly recovers, whereas the latter two taxa show opposite trends due to surface-water oligotrophy. These observations confirm previous results from ODP Site 690 on Maud Rise. The rapid ocean acidification caused intensive dissolution of susceptible holococcoliths and poorly preserved assemblages. Similarities and contrasts between the results of this study and previous work from open-ocean sites and shelf margins further demonstrate that the response to the PETM was consistent in open oceans, but could be localized on continental shelves where nutrient regimes depend on the local geologic setting and oceanographic conditions.