HR: 16:15h
AN: PP32D-02    [PDF]
TI: A Different Look at Gateways - Australian/Antarctic and Drake Passage
AU: * Lawver, L
EM: lawver@ig.utexas.edu
AF: University of Texas Jackson School of Geosciences, 4412 Spicewood Springs Rd, Bldg 600, Austin, TX 78759 United States
AU: Gahagan, L
EM: lisa@utig.ig.utexas.edu
AF: University of Texas Jackson School of Geosciences, 4412 Spicewood Springs Rd, Bldg 600, Austin, TX 78759 United States
AB: A deepwater passageway between Australia and East Antarctica is considered important to the development of the Cenozoic Antarctic icesheet. Identification of magnetic anomalies formed at the Australia-Antarctic ridge makes relative motion of the two continental masses with respect to one another, easy to reconstruct. Unfortunately, exact knowledge of the extent of the true continental margin of East Antarctica is not known. An excellent match of the continental shelf break of East Antarctica with its conjugate section of the southern Australian margin from 124$\deg$E to 133$\deg$E produces an unacceptable overlap of the continental margin of the Coates coast region of Antarctica with the Kangaroo Island section of the southern Australian margin. If the unacceptable overlap is assumed to have originated as post-breakup deposition of glacially-derived sediments deposited on older ocean crust off the outflow region of the Wilkes Land Basin, then the time of the development of a deep seaway between Australia and East Antarctica pre-dates the Eocene-Oligocene boundary (33.5 Ma) by perhaps as much as 7 to 8 million years. Another seaway between Tasmania and the South Tasman Rise may be even older but would not necessarily have been initially the medium depth seaway that it is presently. The South Tasman Rise would have been over a fixed Balleny Islands hotspot during much of the Eocene, resulting in uplift. It passed over the active hotspot and was no longer above it by about 35 Ma which may have resulted in the rapid subsidence seen in the ODP 189 holes at the Eocene-Oligocene boundary. Only if the assumed, continental margin off the Wilkes Land Basin is older than Oligocene and the South Tasman Saddle was above 1000 meters during the Eocene would the opening of a seaway between Australia and East Antarctica have been established as late as 33.5 Ma or at the Eocene-Oligocene boundary.
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting