HR: 0800h
AN: PP41B-0641    [Abstracts]
TI: Diatom Implications of the Neogene Antarctic Glacial History: ODP Leg 178 Site 1095, Antarctic Peninsula
AU: * Iwai, M
EM: iwaim@cc.kochi-u.ac.jp
AF: Department of Natural Environmental Science, Faculty of Science, Kochi University, Akebono-cho 2-5-1, Kochi, Koc 780-8520 Japan
AB: Temporal variations of diatom abundance and species composition at Ocean Drilling Program Leg 178 sites located along the Pacific side of Antarctic Peninsula were analyzed to investigate the paleobathymetric change of the continental shelf in the western Antarctic Peninsula and the N-S oscillations of the Polar Front (PF). The widespread shallow shelf, less than 100 m, was suggested by the occurrence of neritic diatom Paralia sulcata and various benthic diatoms at both continental rise (Site 1095) and shelf (Site 1097) sites. In contrast to the late Miocene, the water depth of the continental shelf deepened, more than 100 m of the shallowest area, after 5.2 Ma. It was suggested by the replacement of the neritic diatoms from P. sulcata to Stephanopyxis spp. The deepening of the continental shelf is considerable as a result of the expanded ice sheet after the latest Miocene. The warming of the Southern Ocean occurred at 5.7, 5.2-4.7, and 4.4-3.6 Ma. The increase of Thalassionema nitzschioides s.l. suggests a southward migration of Antarctic Convergence (AC) to Site 1095 and the summer water temperature increased to 2°-5°C during those time intervals. The water temperature of 2°-5°C in the Pacific sector of the Southern Ocean during the warm period of the early Pliocene was not high enough to cause the collapse of the Antarctic Ice Sheet.
DE: 4207 Arctic and Antarctic oceanography (9310, 9315)
DE: 4279 Upwelling and convergences (4964)
DE: 4944 Micropaleontology (0459, 3030)
DE: 9310 Antarctica (4207)
DE: 9605 Neogene
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005