HR: 16:20h
AN: PP54B-02    [Abstracts]
TI: Timing and Nature of the Deepening of the Tasmanian Gateway
AU: * Stickley, C E
EM: cathy@earth.cf.ac.uk
AF: School of Earth, Ocean and Planetary Sciences, Cardiff University, Park Place, Cardiff, CF10 3YE United Kingdom
AU: Brinkhuis, H
EM: h.brinkhuis@bio.uu.nl
AF: Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD, Utrecht Netherlands
AU: Schellenberg, S A
AF: Department of Geological Sciences, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182 United States
AU: Sluijs, A
AF: Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD, Utrecht Netherlands
AU: Rohl, U
AF: Department of Geosciences, Bremen University, P.O. Box 33 04 40, Bremen, 28334 Germany
AU: Fuller, M
AF: HIGP-SOEST, University of Hawaii, Honolulu, HI, 96822 United States
AU: Grauert, M
AF: Geografisk Institut, Kbenhavns Universitet, ster Voldgade 10, 1350, Kbenhavn Denmark
AU: Huber, M
AF: Earth and Atmospheric Science, Purdue University, Purdue, In United States
AU: Warnaar, J
AF: Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD, Utrecht Netherlands
AU: Williams, G L
AF: Atlantic Geoscience Centre, P.O. Box 1006, Dartmouth, NS, B2Y 4A2 Canada
AB: In the late Paleogene, Australia separated from Antarctica and continued to drift northwards allowing the eventual development of the Antarctic Circumpolar Current (ACC). The exact timing and nature of the opening of this gateway during the Eocene-Oligocene (E/O) transition is of interest in respect to its apparent synchroneity with climate deterioration on continental Antarctica. The recovery of a continuous marine sedimentary record across the E/O transition at 4 sites within the Tasmanian Gateway (TG) during ODP 189, allows detailed paleoenvironmental changes to be documented at high resolution in this region. The critical sedimentary units are barren of calcareous microfossils yet siliceous and organic-walled microfossils (notably diatoms and dinocysts) are abundant and excellently preserved, allowing an integrated and detailed paleoeonvironmental analysis of the E/O transition. We present results from Site 1172 and report on the timing and nature of several step-wise deepening events and paleooceanographic changes across the E/O transition in the TG. We use integrated diatom, dinocyst, geochemical, lithological and physical property data to show that the TG deepened at 35.5 Ma, preceding the E/O Antarctic glaciation event by 2 Ma. Importantly our microfossil data indicate a pre-deepening shallow-water pro-deltaic setting characterized by highly endemic biota influenced by a cool clockwise rotating `proto-Ross Sea gyre', to a post-deepening pelagic setting in the earliest Oligocene characterized by cosmopolitan biota. Interestingly these findings indicate a warming in the TG at the exact time when, according to previous hypotheses, a cool-ACC should be influencing the region. These conclusions are corroborated independently by the modeling results of Huber et al., (in press, Palaeoceanography).
DE: 9604 Cenozoic
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 3030 Micropaleontology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting