HR: 0800h
AN: PP41A-0620    [Abstracts]
TI: Latitudinal distributions and late Quaternary varations of ice-rafted debris on the Antarctic Wilkes Land margin
AU: * Ikehara, M
EM: ikehara@cc.kochi-u.ac.jp
AF: Center for Advanced Marine Core Research, Kochi University, B200 Monobe, Nankoku, Kochi, 783-8502 Japan
AU: Hatakeyama, E
PP41A-0620 AF: Center for Advanced Marine Core Research, Kochi University, B200 Monobe, Nankoku, Kochi, 783-8502 Japan
AU: Ohno, K
PP41A-0620 AF: Center for Advanced Marine Core Research, Kochi University, B200 Monobe, Nankoku, Kochi, 783-8502 Japan
AU: Murayama, M
EM: murayama@cc.kochi-u.ac.jp
AF: Center for Advanced Marine Core Research, Kochi University, B200 Monobe, Nankoku, Kochi, 783-8502 Japan
AU: Kodama, K
EM: kdma@cc.kochi-u.ac.jp
AF: Center for Advanced Marine Core Research, Kochi University, B200 Monobe, Nankoku, Kochi, 783-8502 Japan
AB: The latitudinal migration of the oceanic fronts and sea-ice coverage in the Southern Ocean should have an influence on the surface water circulation, as well as primary productivity, heat transport, and temperature gradient. Glacial advance and retreat are also major influence to the sediment distribution and sedimentary process across the continental margin of the Antarctica during the late Quaternary. Surface sediments were collected from a latitudinal transect (from 47.5°S to 65.5°S) in the Australian sector of the Southern Ocean during the two cruises KH94-4 and KH01-3 by R/V Hakuho-Maru. We analyzed for these sediments by the X-ray CT scan, ice-rafted debris (IRD) counts, grain size analysis, organic carbon contents, and biomarkers. In addition, we used a sediment core collected at near Antarctic continental slope (AMR-2PC, 64.66° S, 139.98°E, WD 2965m) to reconstruct the past variations of glacial ice distribution and sedimentary condition. Age model of the core was established by diatom biostratigraphy and relative paleointensity curve of the geomagnetic field. The amount of dropstones (> 2 mm) and IRD (>150 micrometer) preserved in the latitudinal surface sediments were decreased toward the northern sites, and apparent northern edge of the observed IRD was located at 60°S. These results indicate that the modern iceberg reaches up to about 60°S in the Australian sector of the Southern Ocean. Grain size distributions of non-biogenic particles in the surface sediments near Antarctica are clearly larger than those of pelagic sites at about 60°S. These results suggest that the ice-rafting process and gravity flow from the Antarctic ice sheet contributes largely to the deposition of the Wilkes Land margin sediments. At the core AMR-2PC, the amount of IRD was decreased during the glacials (MIS 2, 6, and 8) and was increased during interglacials (MIS 1, 5 and 7). Interglacial sedimentation is dominated by hemiperagic deposition of biogenic particles and terrigenous clasts by IRD. On the other hand, the biogenic productivity and IRD supply were extremely decreased during the glacials, suggesting that the perennial ice covered the surface ocean over the core site off Wilkes Land margin during glacial periods.
DE: 0750 Sea ice (4540)
DE: 1621 Cryospheric change (0776)
DE: 3022 Marine sediments: processes and transport
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005