Tuesday, 28 August 2007 - 2:30 PM
2.P1.A-4

East Antarctic Ice Sheet fluctuations during the Middle Miocene Climatic Transition inferred from faunal and biogeochemical data on planktonic foraminifera (Kerguelen Plateau)

Marina Verducci1, Luca M. Foresi1, George H. Scott2, Massimo Tiepolo3, Mario Sprovieri4, and Fabrizio Lirer4. (1) Department of Earth Sciences, University of Siena, Via Laterina, 8, Siena, 53100, Italy, (2) GNS Science, 1 Fairway Drive, Lower Hutt, 30368, New Zealand, (3) Istituto di Geoscienze e Georisorse, C.N.R., Via Ferrata, 1, Pavia, 27100, Italy, (4) Istituto per l'Ambiente Marino Costiero, C.N.R., Calata Porta di Massa, Napoli, 80100, Italy

This research focuses on a detailed study of faunal and biogeochemical changes that occurred in the Kerguelen Plateau region from 14.8 to 11.8 Ma. Abundance fluctuations of different planktonic foraminiferal taxa, d18O and Mg/Ca data have been integrated to feature the East Antarctic Ice Sheet (EAIS) growth modality and fluctuations during the Middle Miocene Climatic Transition. A 7°C lowering in seawater temperature, an abrupt turnover in the foraminiferal fauna, a 1.5‰ shift in d18O and a shift in seawater d18O around 13.9-13.7 Ma, are interpreted to reflect surface water cooling and EAIS expansion. Hole 747A data suggest a major change in the variability of the climate system: ice sheet fluctuations were greater before 13.9 Ma compared with those from 13.7 Ma, when the EAIS was more stable. The middle Miocene episode of Antarctic ice sheet expansion represents a first step towards the development of the modern permanent ice sheet.

[Manuscript]

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