Earth and Atmospheric Sciences, Department of



Tim R. Naish, Institute of Geological and Nuclear Sciences (Lower Hutt, New Zealand)
Ken J. Woolfe, James Cook University
Peter J. Barrett, Vistoria University of Wellington
Gary S. Wilson, University of Oxford
Cliff Atkins, Vistoria University of Wellington
Steven M. Bohaty, University of Nebraska-Lincoln
Christian J. Bücker, RWE-DEA AG (Hamburg, Germany)
Michele Claps, North Caspian Operating Company (The Hague, Netherlands)
Fred J. Davey, Institute of Geological and Nuclear Sciences (Lower Hutt, New Zealand)
Gavin B. Dunbar, James Cook University
Alistair G. Dunn, National Institute of water and Atmospheric Research (Wellington, New Zealand)
Christopher R. Fielding, University of QueenslandFollow
Fabio Florindo, University of Southampton
Michael J. Hannah, Vistoria University of Wellington
David M. Harwood, University of Nebraska-LincolnFollow
Stuart A. Henrys, Institute of Geological and Nuclear Sciences (Lower Hutt, New Zealand)
Lawrence A. Krissek, Ohio State University
Mark Lavelle, British Antarctic Survey
Jaap van der Meer, University of London
William C. McIntosh, New Mexico Institute of Mining and Technology
Frank Niessen, Alfred-Wegener-Institute
Sandra Passchier, Ohio State University
Ross D. Powell, Northern Illinois University
Andrew P. Roberts, University of Southampton
Leonardo Sagnotti, Istituto Nazionale di Geofisica e Vulcanologia (Roma, Italy)
Reed P. Scherer, Northern Illinois University
C. Percy Strong, Institute of Geological and Nuclear Sciences (Lower Hutt, New Zealand)
Franco Talarico, Università degli Studi di Siena
Kenneth L. Verosub, University of California - Davis
Giuliana Villa, Università degli Studi di Parma
David K. Watkins, University of Nebraska-LincolnFollow
Peter-N. Webb, Ohio State University
Thomas Wonik, Institut für Geowissenschaftliche Gemeinschaftsaufgaben

Date of this Version



Published in Nature (October 18, 2001) 423: 719-723.


Between 34 and 15 million years (Myr) ago, when planetary temperatures were 3-4°C warmer than at present and atmospheric CO2 concentrations were twice as high as today, the Antarctic ice sheets may have been unstable. Oxygen isotope records from deep-sea sediment cores suggest that during this time fluctuations in global temperatures and high-latitude continental ice volumes were influenced by orbital cycles. But it has hitherto not been possible to calibrate the inferred changes in ice volume with direct evidence for oscillations of the Antarctic ice sheets. Here we present sediment data from shallow marine cores in the western Ross Sea that exhibit well dated cyclic variations, and which link the extent of the East Antarctic ice sheet directly to orbital cycles during the Oligocene/Miocene transition (24.1-23.7 Myr ago). Three rapidly deposited glaci-marine sequences are constrained to a period of less than 450 kyr by our age model, suggesting that orbital influences at the frequencies of obliquity (40 kyr) and eccentricity (125 kyr) controlled the oscillations of the ice margin at that time. An erosional hiatus covering 250 kyr provides direct evidence for a major episode of global cooling and ice-sheet expansion about 23.7 Myr ago, which had previously been inferred from oxygen isotope data (Mi1 event).