Tuesday, 28 August 2007 - 11:50 AM
2.A.A-6
Insights into the East Antarctic Ice Sheet, 3.5 to 19 Ma, inferred from iceberg provenance
Trevor Williams1, Tina Van de Flierdt1, Elena Chung2, Martin Roy3, Sidney R. Hemming1, Steven L. Goldstein1, Maria Abrahamowicz4, and Bruno Tremblay4. (1) Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY 10964, (2) University of Maryland, College Park, MD 20742, (3) Départment des Sciences de la Terre, Université du Québec à Montréal, C.P. 8888, Succ. Centre-Ville, Montréal, QC QC H3C 3P8, Canada, (4) Atmospheric and Ocean Sciences, McGill University, Montreal, QC H3A 2K6, Canada
ODP Site 1165, 400 km offshore of Prydz Bay, Antarctica, is well located to record changes in ice-rafted debris (IRD) and iceberg provenance. The potential sources of IRD, Prydz Bay and the coast to the east, have distinct neodymium and argon isotopic signatures. Eight IRD-bearing layers from Site 1165 were analyzed; they record snapshots of ice and ocean conditions from 3.5 to 19 Ma. Based on argon analyses of individual hornblende IRD grains, a major provenance change is observed: before 14 Ma, IRD is locally sourced from the Prydz Bay sector, whereas after 7 Ma, roughly half the IRD probably comes from Wilkes Land, Adelie Land, and as far as George V Land. This is likely associated with ice expansion on East Antarctica after the mid-Miocene. Additionally, an iceberg drift model has been developed to assess the ocean and climate conditions required to produce the IRD provenance observations.