Download Onshore - offshore East Antarctica

Frontiers and Opportunities in Antarctic Geosciences * Certosa di Pontignano * 29-31 July 2004
Onshore-offshore East Antarctica
L.A. LAWVER, L.M. GAHAGAN, D. BLANKENSHIP, I.W.D. DALZIEL
Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin,
4412 Spicewood Springs Road #600 Austin, TX 78759-8500 U.S.A.
*Corresponding author ([email protected])
Understanding the initiation and consequences of East Antarctic glaciation is critical to determining the inputs needed for
global climate change during the Tertiary. The ICECAP project, a joint USA-UK proposal to fly aerogeophysics over East
Antarctica will allow us to make a better determination of the sub-ice topography for East Antarctica. The present sub-ice
topography, available from the BEDMAP project [Lythe et al., 2000], is an improvement on the earlier sub-ice elevation
map of Drewry and Jordan [1983]. The primary difference between the two charts is the greater definition of some of the
larger highlands, such as the Belgica Subglacial Highlands and the Gamburtsev Mountains. Modeling of initiation of East
Antarctic ice sheet development requires knowledge of the Eocene elevation and extent of the higher regions of East
Antarctica.
Formation of the East Antarctic ice sheet generated deposition of large volumes of glacial till and other sediments that
prograde off the East Antarctic margin particularly where large outflow is possible. The extent of the glacially deriveddeposition off the Wilkes Subglacial Basin between 140˚ and 155˚E directly determines the time of opening of a deep water
Australia-Antarctica seaway. If the continental margin of Antarctica is located by the satellite gravity anomaly off Oates
Land then a deepwater seaway did not open between Australia and Antarctica until 33.5 Ma. If part of what is believed to
be continental along that margin is in fact deposition of glacially derived sediments on older oceanic crust, then a deepwater
seaway may have been open 5 to 8 million years earlier. The area in question is generally ice-covered and virtually no
shipboard work has been carried out in this region. New techniques need to be developed to determine the crustal structure
of this area.
Another region critical to our understanding of the break up of Gondwana is the Antarctic margin where India and Sri
Lanka were situated. Clearly identified, correlated and lineated magnetic anomalies have yet to be found either along this
margin or its conjugate in the Bay of Bengal. An aerogeophysical survey along the Wilkes Land margin would be a useful
tool although present logistics make such work difficult.
REFERENCES
Drewry, D.J. and Jordon, S.R., 1983. The Bedrock Surface of Antarctica, Sheet 3, in: D.J. Drewry (ed.) Antarctica: Glaciological and Geophysical Folio,
Scott Polar Research Institute, Cambridge, ISBN 0-901021-040-0.
Lythe, M.B., Vaughan, D.G. and the BEDMAP Consortium. 2000. BEDMAP - bed topography of the Antarctic. 1:10,000,000 scale map. BAS (Misc) 9.
Cambridge, British Antarctic Survey.