Friday, 31 August 2007 - 10:40 AM
5.A.D-1
Detrital apatite and zircon (U-Th)/He evidence for early formation and slow erosion of the Gamburtsev Mountains, East Antarctica
Stephen E. Cox1, Sidney R. Hemming1, Peter W. Reiners2, Stefan Nicolescu2, Stuart N. Thomson3, George E. Gehrels2, Tina van de Flierdt1, Steven L. Goldstein1, and Stefanie A. Brachfeld4. (1) Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964, (2) Department of Geosciences, University of Arizona, 1040 E 4th St., Tucson, AZ 85721, (3) Department of Geology & Geophysics, Yale University, PO Box 201809, New Haven, CT 06520, (4) Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ 07043
The enigmatic Gamburtsev Subglacial Mountains in East Antarctica are important as the postulated source point for Eocene glaciation, but have not been sampled directly because they are covered by 0.6-4 km of ice. Topography and ice flow suggest that they shed terrigenous sediment to the Lambert Graben-Prydz Bay Basin. We measured (U-Th)/He ages of 110 to 316 Ma on detrital apatite grains and 197 to 397 Ma on detrital zircon grains (of pan-African U-Th-Pb age) from Prydz Bay cores. Hornblende and biotite 40Ar/39Ar ages from these samples cluster around 500 Ma, representing rapid exhumation following the pan-African high grade metamorphism represented in U-Th-Pb ages. Combined zircon and apatite (U-Th)/He cooling models require gradual, slow cooling since about 500 Ma with erosion rates of 0.03 km/Ma or less. Models that require rapid uplift and erosion or recent formation of the Gamburtsev Mountains appear to be eliminated by these data.