HR: 0800h
AN: C51A-0074    [Abstracts]
TI: Cenozoic East Antarctic Ice Sheet Evolution From Wilkes Land Continental Margin Sediments and IODP Drilling in 2009
AU: * Escutia, C
EM: cescutia@ugr.es
AF: Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad d Granada, Fuentenueva, s/n, Granada, 18002, Spain
AU: Cooper, A
EM: akcooper@pacbell.net
AF: Department of Geological and Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, United States
AU: Eittreim, S
EM: akcooper@pacbell.net
AF: Unites States Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025, United States
AU: Tanahashi, M
EM: tanahashi-m@aist.go.jp
AF: Geological Survey of Japan Geological Survey of Japan, Site C-7, 1-1-1, Higashi, Tsukuba, 305-8567, Japan
AU: Ishihara, T
EM: ishihara-t@aist.go.jp
AF: Geological Survey of Japan Geological Survey of Japan, Site C-7, 1-1-1, Higashi, Tsukuba, 305-8567, Japan
AU: De Santis, L
EM: ldesantis@ogs.trieste.it
AF: Geofisica Sperimentale, Borgo Grotta Gigante 42/c, Sgonico, 34010, Italy
AU: O'Brien, P
EM: phil.obrien@ga.gov.au
AF: AU: Domack, E
EM: edomack@hamilton.edu
AF: Hamilton College, Clinton, Clinton, NY 13323, United States
AU: Dunbar, R
EM: dunbar@stanford.edu
AF: Stanford University, Stanford, Stanford, CA 94305, United States
AB: The long-term history of glaciation along the East Antarctic Wilkes Land margin is inferred using an integrated geophysical and geological approach. We postulate that the first arrival of the ice to the Wilkes Land continental shelf resulted in the development of a large unconformity (WL-U3) between 33.42 and 30 Ma. Above WL-U3, substantial margin progradation takes place with early glacial strata (e.g., outwash deposits) deposited as low- angle prograding foresets by temperate glaciers. The change in geometry of the prograding wedge across regional unconformity WL-U8 is interpreted to represent the transition, during the late Miocene-Pliocene, from a glacial regime characterized by a warm dynamic ice sheet (i.e., ice sheets come and go) to a regime dominated by a cold-based and persistent ice sheet. The steep foresets above WL-U8 likely consist of ice proximal sediments (i.e., water-lain till and debris flows) deposited when grounded ice-sheets extended into the shelf. On the continental rise, shelf progradation above WL-U3 results in an up-section increase in the energy of the depositional environment (i.e., seismic facies indicative of more proximal turbidite and of bottom contour current deposition from the deposition of the lower WL-S5 sequence to WL-S7). Maximum rates of sediment delivery to the rise occur during the development of sequences WL-S6 and WL-S7, inferred to be of middle Miocene age. During deposition of the two uppermost sequences (WL-S8 and WL-S9), there is a marked decrease in the sediment supply to the lower continental rise and a shift in the depocenters to more proximal areas of the margin. We believe WL-S8 records sedimentation during the final transition from a dynamic to a persistent but oscillatory ice sheet in this margin during the late Miocene. Sequence WL-S9 forms under polar regime during the Pliocene–Pleistocene, when most sediment delivered to the margin is trapped in the outer shelf and slope forming steep prograding wedges. During the warmer but still polar, Holocene, biogenic sediment accumulates quickly in deep inner-shelf basins during the high-stand intervals. These sediments contain an ultrahigh resolution (annual to millennial) record of climate variability. Drilling of the Wilkes Land margin by IODP scheduled for 2009 is designed to test the above inferred ages and history of glaciation. Drilling of the Wilkes Land margin will be a contribution by the ACE (Antarctic Climate Evolution) Program of SCAR (Scientific Committee on Antarctic Research) to the forthcoming International Polar Year.
DE: 0726 Ice sheets
SC: Cryosphere [C]
MN: 2007 Fall Meeting