HR: 17:20h
AN: PP54B-06    [Abstracts]
TI: Arctic Dinoflagellate Migration Marks the Oligocene Glacial Maximum: Implications for the Rupelian-Chattian Boundary
AU: * Van Simaeys, S
EM: stefaan.vansimaeys@geo.kuleuven.ac.be
AF: Stefaan Van Simaeys, Historical Geology, University of Leuven, Redingenstraat 16 B-3000 Leuven, Belgium, Leuven, 3000 Belgium
AU: Brinkhuis, H
EM: h.brinkhuis@bio.uu.nl
AF: Henk Brinkhuis, Department of Palaeoecology, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands, Utrecht, 3584 CD Netherlands
AU: Pross, J
EM: joerg.pross@uni-tuebingen.de
AF: J”rg Pross, Institut fr Geowissenschaften, Universit„t Tbingen, Sigwartstraįe 10, D-72076 Tbingen, Germany, Tbingen, 72076 Germany
AU: Williams, G L
EM: gwilliam@gsca.NRCan.gc.ca
AF: Graham L. Williams, Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, PO Box 1006, Dartmouth NS B2Y 4A2, Canada, Dartmouth, NS B2Y 4A2 Canada
AU: Zachos, J C
EM: jzachos@emerald.ucsc.edu
AF: James C. Zachos, University of California, Santa Cruz, Earth Science Department, CA 95064, USA., Santa Cruz, CA 95064 United States
AB: Various geochemical and biotic climate proxies, and notably deep-sea benthic foraminiferal $\delta$$^{18}$O records indicate that the Eocene 'greenhouse' state of the Earth gradually evolved towards an earliest Oligocene 'icehouse' state, eventually triggering the abrupt appearance of large continental ice-sheets on Antarctic at $\sim$33.3 Ma (Oi-1 event). This, however, was only the first of two major glacial events in the Oligocene. Benthic foraminiferal $\delta$$^{18}$O records show a second positive excursion in the mid Oligocene, consistent with a significant ice-sheet expansion and/or cooling at 27.1 Ma (Oi-2b) coincident with magnetosubchron C9n. Here, we report on a mid Oligocene, globally synchronous, Arctic dinoflagellate migration event, calibrated against the upper half of C9n. A sudden appearance, and abundance increases of the Arctic taxon {\it Svalbardella} at lower-middle latitudes coincides with the so-called Oi-2b benthic $\delta$$^{18}$O event, dated at $\sim$27.1 Ma. This phenomenon is taken to indicate significant high-latitude surface water cooling, concomitant Antarctic ice-sheet growth, and sea level lowering. The duration of the {\it Svalbardella} migrations, and the episode of profound cooling is estimated as $\sim$500 ka, and is here termed the Oligocene Glacial Maximum (OGM). Our records suggest a close link between the OGM, sea-level fall, and the classic Rupelian-Chattian boundary, magnetostratigraphically dating this boundary as $\sim$27.1 Ma.
DE: 4806 Carbon cycling
DE: 4267 Paleoceanography
DE: 1620 Climate dynamics (3309)
DE: 0315 Biosphere/atmosphere interactions
DE: 0325 Evolution of the atmosphere
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting