Abrupt turnover in calcareous-nannoplankton assemblages across the Paleocene/Eocene Thermal Maximum: implications for surface-water oligotrophy over the Kerguelen Plateau, Southern Indian Ocean

• Main Authors: Shijun Jiang, Sherwood W. Wise
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; Indian; Kerguelen; Maud Rise; Southern Ocean; Antarc*; Antarctica
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.490.3967; http://pubs.usgs.gov/of/2007/1047/srp/srp024/of2007-1047srp024.pdf

Ocean sector of the Southern Ocean represents only the second complete, expanded sequence through the Paleocene/Eocene Thermal Maximum (PETM; ~55 Ma) recovered from Antarctic waters. Calcareous nannoplankton at this site underwent an abrupt, fundamental turnover across the PETM as defined by a carbon isotope excursion. 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 elevated pCO2 that accompanied the PETM caused a shoaling of the lysocline and carbonate compensation depth, leading to intensive dissolution of susceptible holococcoliths and poor preservation of the 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-ocean environments, but could be localized on continental shelves where nutrient regimes depend on the local geologic setting and oceanographic conditions. Citation: Jiang, S., and S.W. Wise (2007), Abrupt turnover in calcareous-nannoplankton assemblages across the Paleocene/Eocene Thermal Maximum: implications for surface-water oligotrophy over the Kerguelen Plateau, Southern Indian Ocean, in Antarctica: A Keystone in a Changing