HR: 14:45h
AB: Kennett (1977) correctly deduced many of the tectonic causes of the Cenozoic evolution of both Antarctic glaciation and global paleoceanography. Compilation of a global database of marine magnetic anomalies and fracture zone lineations based on satellite derived gravity has enabled the UTIG Plates Project to produce an absolute plate tectonic framework for major plate motions during the Cenozoic. Constraints on the opening of a middle to deep water passageway between South America and Antarctica can be established based on motions of South America, Africa and Antarctica. Initial opening between Australia and East Antarctica may have produced a widening ocean during the early Cenozoic but only a shallow seaway existed across the South Tasman Rise until it cleared East Antarctica in the Oligocene. During the Cretaceous, ocean circulation was dominated by circum-equatorial movement of water masses with substantial circulation through a Tethyean seaway. The collision of India with Eurasia closed the Tethyean seaway and diverted circulation from north of Africa (approximately $30\deg$N in the Paleocene) to south of Africa (approximately $45\deg$S). While the opening of seaways between Australia and Antarctica and South America and the Antarctic Peninsula may have had a rapid impact on paleoceanographic indicators such as found in $\delta$O$^{18}$ values from forams drilled on Maud Rise, opening and closing of equatorial seaways, in particular the Isthmus of Panama may have resulted in the more substantial long-term impact on Cenozoic and recent climate. In short, while opening of Drake Passage and a passage south of Australia are necessary for the development of the Antarctic Circumpolar Current (ACC), simply opening these paleoseaways is not sufficient to produce vigorous circumpolar circulation. We will show a series of reconstructions that illustrate the major plate motions through the Cenozoic and their impact on the width and depth of Drake Passage as well as the opening between Australia and East Antarctica. Kennett, J.P., 1977, Cenozoic Evolution of Antarctic Glaciation, the Circum-Antarctic Ocean, and Their Impact on Global Paleoceanography, J. Geophys. Res. 82, 3843-3859.
AN: OS72F-06 INVITED
TI: What Major Plate Motions tell us About the Opening of Drake Passage.
AU: * Lawver, L A
EM: lawver@ig.utexas.edu
AF: University of Texas at Austin, Institute for Geophysics, 4412 Spicewood Springs Rd #600, Austin, TX 78759-8500 United States
AU: Gahagan, L M
EM: plates@ig.utexas.edu
AF: University of Texas at Austin, Institute for Geophysics, 4412 Spicewood Springs Rd #600, Austin, TX 78759-8500 United States
DE: 8157 Plate motions--past (3040)
DE: 9310 Antarctica
DE: 9604 Cenozoic
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 4207 Arctic and Antarctic oceanography
SC: OS
MN: Fall Meeting 2000