Role of Coccolithophores During a ``Warm Pulse'' in the Atlantic Antarctic Sector: The MIS 31 in ODP Site 1094

HR: 0800h
AN: PP41B-0650 [Abstracts]
TI: Role of Coccolithophores During a ``Warm Pulse'' in the Atlantic Antarctic Sector: The MIS 31 in ODP Site 1094
AU: * Flores, J
EM: flores@usal.es
AF: Universidad de Salamanca, Departamento de Geolog｛. Facultad de Ciencias, Salamanca, 37008 Spain
AU: Sierro, F J
EM: sierro@usal.es
AF: Universidad de Salamanca, Departamento de Geolog｛. Facultad de Ciencias, Salamanca, 37008 Spain
AU: Scherer, R
EM: t60rps1@wpo.cso.niu.edu
AF: Northern Illinois University DeKalb, Department of Geology and Environmental Geosciences Northern Illinois University DeKalb, Illinois, IL 60115 815- United States
AU: Dunbar, R
EM: dunbar@stanford.edu
AF: Stanford University, Department of Geological and Environmental Sciences, Stanford, CA 94305-2115 United States
AB: ODP Site 1094 was the southernmost site drilled during Leg 177 and is located South of the Polar Front at 53.2°S, 5.1°E. The recovered sediment is characterized by diatom oozes with variable concentrations of calcareous nannofossils and foraminifers. Detailed calcareous nannofossil stratigraphic analysis allowed recognition of an interval characterized by the dominance of rounded and robust specimens of Reticulofenestra asanoi. The excellent geomagnetic record permitted the re-calibration of the FO and LO of R. asanoi at an age of 1107 and 887 ky (subchrons C1r.1n and C1r.2r), respectively. MIS 31 is characterized by an important increase in the accumulation of calcium carbonate, mainly due to an increase in production of calcareous nannofossils and planktonic foraminifers, allowing the possibility to analyze the stable isotope record. We observe a correlation between light d18O, d13C values and total coccoliths. A detailed analysis of the coccolithophore assemblages allows us to show relatively rapid and abrupt changes. Maxima in d13C coincide with peaks in diversity, especially noteworthy between 130 and 128.5 mbsf (after the reversal C1r.1n, at126.96 mbsf± 1m). This interval is characterized by an increase of small Gephyrocapsa (< 3 microns), Helicosphaera carteri, Calcidiscus leptoporus and, in minor proportion, Coccolithus pelagicus. Although the record of coccolithophores is obviously controlled by changes in surface water temperature, linked to southern displacement of the polar front and other related oceanographic features, the variations observed in MIS 31 in the Antarctic sector seems to be controlled by changes in other parameters such as nutrient availability and salinity, linked to ice melting.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4940 Isotopic stage
DE: 4944 Micropaleontology (0459, 3030)
DE: 4950 Paleoecology
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005