HR: 0800h
AN: PP51E-1362 INVITED     [Abstracts]
TI: Tertiary Sedimentation Patterns on the Wilkes Land Margin, Antarctica (100-140E)
AU: * Close, D I
EM: david.close@worc.ox.ac.uk
AF: Dept. of Earth Science, University of Oxford, Parks Road, Oxford, OX13PR United Kingdom
AU: Stagg, H M
EM: howard.stagg@ga.gov.au
AF: Geoscience Australia, GPO Box 378, Canberra, ACT 2601 Australia
AU: Bindoff, N L
EM: n.bindoff@utas.edu.au
AF: Institute of Antarctic & Southern Ocean Studies, University of Tasmania, Churchill Avenue, Sandy Bay, Hobart, Tas 7005 Australia
AU: Watts, T B
EM: tony@earth.ox.ac.uk
AF: Dept. of Earth Science, University of Oxford, Parks Road, Oxford, OX13PR United Kingdom
AB: During the Austral summers of 2000-01 and 2001-02, Geoscience Australia (GA) acquired over 4000 km of seismic reflection profile data across the Wilkes Land margin, Antarctica. Two major unconformities are recognised in these data that can be traced for over 1500 km along the margin. The deeper of these unconformities is related to the breakup of Australia and Antarctica at $\sim$85-90 Ma. The upper unconformity is the base of an onlapping reflector sequence beneath the continental slope. On the basis of correlation with similar stratal character in southern Australian margin data, we infer a base Eocene (50 Ma) timing for this unconformity. Compilation of sediment thickness data provides the first regional sediment isopach for the Wilkes Land margin. A previously unrecognised sedimentary basin is identified off west Wilkes Land. This basin comprises a sediment thickness of $>$5 s two-way-time (TWT), $\sim$9 km. The volume of sediments within this basin is comparable to the major river deltas of other continents, such as the Niger and Amazon deltas. A distinct west to east asymmetry exhibited by the basin indicates that deep-water currents have been an important control on sediment transport and deposition on the East Antarctic margin since at least the onset of regional Antarctic glaciation, $\sim$34 Ma. If eastward flowing deep-water currents are the primary agent of sediment transport within this basin, a modern analogue current is not well established by current oceanographic data. The modern day geostrophic currents primarily flow westward on the Wilkes Land margin; and the southern boundary of the eastward flowing Antarctic Circum-polar Current (ACC) occurs at the northern limits of the basin. A change in current circulation patterns may explain the contrary observations of westward flowing currents and eastward distributed sediments. However, the sediment distribution may represent a more southerly circulation axis of the ACC prior to the formation of continent-wide, frozen based glaciers at $\sim$9 Ma. The locus of thickest sediments occurs offshore of the termination of the Totten Glacier, a major fast-flow feature in East Antarctica. This indicates that major ice-streams and/or flowing glaciers may be very long lived, $>$10 My, despite observations of shorter term changes in glaciomorphological features.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3022 Marine sediments--processes and transport
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting