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norris

HR: 11:35h
AN: PP52B-06
TI: Equatorial Pacific ``stable isotope reference curve'' for the Oligocene
AU: * Pälike, H
EM: heiko@noc.soton.ac.uk
AF: National Oceanography Centre, Southampton, School of Ocean and Earth Science European Way, Southampton, SO14 3ZH United Kingdom
AU: Norris, R
EM: RNorris@ucsd.edu
AF: Scripps Institution of Oceanography,University of California-San Diego, MS-0244, 308 Vaughan Hall, La Jolla, CA 92093-0244 United States
AU: Herle, J O
EM: Jens.Herrle@liverpool.ac.uk
AF: Department of Earth and Ocean Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP United Kingdom
AU: Wilson, P A
EM: Paul.A.Wilson@noc.soton.ac.uk
AF: National Oceanography Centre, Southampton, School of Ocean and Earth Science European Way, Southampton, SO14 3ZH United Kingdom
AU: Lear, C H
EM: carrie@earth.cf.ac.uk
AF: School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3YE United Kingdom
AU: Coxall, H K
EM: hkc@gso.uri.edu
AF: School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3YE United Kingdom
AU: Tripati, A K
EM: atri02@esc.cam.ac.uk
AF: Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ United Kingdom
AB: We present an uninterrupted chronology of climate and ocean carbon chemistry from ODP Site 1218 recovered in the equatorial Pacific, from the Eocene / Oligocene to the Oligocene / Miocene boundary, ~34 to 23 Ma. Using astronomically age calibrated data we find a strong imprint of the 405, 127 and 96-thousand-year (kyr) Earth's eccentricity as well as a dominant influence of the 1.2 million year (Myr) obliquity amplitude modulation cycles on periodically re-occurring Oligocene glacial and carbon cycle events. In combination, these astronomical modulations act as the ``heartbeat'' of the Oligocene climate system. The response of the climate system to intricate orbital variations is striking and suggests a fundamental role of the carbon cycle in the interaction between solar forcing and climate. Our record provides a new high-resolution view of the Oligocene climate system, prompts a re-evaluation of the previously hypothesised late Oligocene deglaciation, and sheds new light on Oligocene inter-ocean isotope gradients. Salient observations include foraminiferal benthic stable oxygen and carbon isotopes that co-vary, a phase lag of δ¹³C w.r.t. δ¹⁸O for the 405 kyr cycle, preferential filtering of longer orbital periods in δ¹³C, presumably due to σCO₂ reservoir buffering. We then use simple orbitally forced carbon cycle box models and manage to re-create the patterns observed in our data, including the overall strong amplitude of 405 kyr cycles in δ¹³C. Depending on ice-sheet presence and pCO₂ concentrations, our model predicts re-occurring conditions favouring glaciations every 2.4 Myr, including the Eocene/Oligocene transition.
DE: 3036 Ocean drilling
DE: 4926 Glacial
DE: 4946 Milankovitch theory
DE: 9355 Pacific Ocean
DE: 9606 Paleogene
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005