HR: 0800h
AN: PP51A-0200    [Abstracts]
TI: Evidence for Early Cenozoic glaciation from a record of seawater δ¹⁸O at ODP Site 1209: Exploring the paradigm of an ‘ice-free' Middle Eocene
AU: Dawber, C
EM: cfd25@esc.cam.ac.uk
AF: University of Cambridge, Department of Earth Sciences Downing Street, Cambridge, Cam CB2 3EQ, United Kingdom
AU: * Tripati, A
EM: atri02@esc.cam.ac.uk
AF: University of Cambridge, Department of Earth Sciences Downing Street, Cambridge, Cam CB2 3EQ, United Kingdom
AB: The onset of the Cenozoic ‘greenhouse-icehouse' transition is poorly constrained, with the Middle Eocene often considered the intermediary ‘doubthouse' phase. Most benthic foraminiferal oxygen isotope (δ¹⁸O) reconstructions typically assume ‘ice-free' conditions during this period. However, the occurrence of high- frequency sea-level change of tens of meters in the sequence stratigraphic record, is best explained by glacioeustacy [e.g., 1]. To explore the paradigm of an ‘ice-free' Middle Eocene, we discuss a high-resolution record of seawater δ¹⁸O from Ocean Drilling Project (ODP) Site 1209 in the northern tropical Pacific Ocean. The new seawater δ¹⁸O record for ODP Site 1209 indicates two major glacial episodes occurred at ~44.8 and 42.7 Ma, with excursions of greater than 1‰. The amplitude of these excursions necessitate the presence of ice in the southern and northern polar regions at these times, consistent with other records of seawater δ¹⁸O [2] and ice-rafting debris [3,4]). We also evaluate the seawater δ¹⁸O-sea-level calibration accounting for potential biases arising from carbonate ion concentration, Cenozoic ice δ¹⁸O composition and additional ice storage as a result of glacioeustatic sea level fall. [1] Browning, J., Miller, K., and Pak, D., 1996, Global implications of lower to middle Eocene sequence boundaries on the New Jersey coastal plain: The icehouse cometh, Geology, 24, 639-642. [2] Tripati, A., Backman, J., Elderfield, H. and Ferretti, P., 2005, Eocene bipolar glaciation associated with global carbon cycle changes, Nature 436, 341–346. [3] Moran, K., Backman, J., et al., 2006, The Cenozoic palaeoenvironment of the Arctic Ocean, Nature, 441, 601–605. [4] Shorttle, O., Tripati, A. Eagle, E., Dawber, F., Morton, A., Dowdeswell, J., Atkinson, K., Bahé, Y., Shaw, R., Thanabalasundaram, L., Khadun, E., 2007, Evidence for Northern Hemisphere glaciation back to 44 Ma from ice- rafted debris in the Greenland Sea, Fall AGU Abstract.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting