HR: 0800h
AN: U31A-0012    [Abstracts]
TI: The Thermal Evolution of the Western Equatorial Pacific During the Midde and Early Pleistocene
AU: * Medina, M A
EM: martinmedina@umail.ucsb.edu
AF: Geological Sciences, University of California Santa Barbara, Santa Barbara, CA 93101 United States
AU: Lea, D W
EM: lea@geol.ucsb.edu
AF: Geological Sciences, University of California Santa Barbara, Santa Barbara, CA 93101 United States
AU: Spero, H J
EM: spero@geology.ucdavis.edu
AF: Geology, University of California Davis, Davis, CA 95616 United States
AB: Magnesium/calcium data from planktonic foraminifera in the equatorial Pacific sediment cores suggested that tropical Pacific sea surface temperatures (SST's) were about 3 deg.C colder than modern conditions during glacial episodes of the last 500 thousand years (ky). We have extended the Western Equatorial Pacific (WEP) Globigerinoides ruber Mg/Ca and d18O records, from the Ontong Java Plateau, Ocean Drilling Program Hole 806B (0 19.11'N, 159 21.69'E, 2520m), back to 1.3 ma. For temperature conversion we used a G. ruber calibration based on core-tops from the tropical Pacific (Lea and Martin, 1996), which yields the following relationship: Mg/Ca(mmol/mol)= 0.30exp[0.089 X SST deg. C)]. Our SST record shows that the previously observed 3 deg C-colder SST's than modern conditions during glacial episodes are generally the rule for the entire 1.3 ma period. Glacial-interglacial temperature differences as great as 4 deg. C are observed, even in the Early Pleistocene (1-1.8 ma). Preliminary observations suggest the presence of ~40 Ky SST cycles during the Early Pleistocene, of similar amplitude to the dominant SST cycles seen in Late Pleistocene Tropical records. Early Pleistocene WEP SST's, as suggested by our record, oscillated between 26 and 30 deg. C. MIS 11 stands out as the most prominent feature of the WEP SST record. The potential bias on temperature estimates due to the influence of changes in lysocline depth (Farrell and Prell, 1989) and decrease preservation with depth (Lea et al., 2000) is ñ 0.8 deg.C. Preliminary point to point comparison between the SST and the d18O records shows that Mg/Ca-based temperatures lead over d18O by about 3 ky as previously determined by Lea et al. (2000).
DE: 3344 Paleoclimatology
DE: 4231 Equatorial oceanography
DE: 4267 Paleoceanography
DE: 4500 OCEANOGRAPHY: PHYSICAL
SC: Union [U]
MN: 2004 AGU Fall Meeting