Friday, 31 August 2007
5.PS-150
Buried Oligocene glacial topography beneath a smooth middle Miocene unconformity in the southeast Ross Sea: evolution of West Antarctic glaciation
Christopher C. Sorlien1, Douglas S. Wilson2, Bruce P. Luyendyk1, Louis R. Bartek3, Robert C. Decesari2, and John B. Diebold4. (1) Institute for Crustal Studies, UCSB, Santa Barbara, CA 93106, (2) Dept Earth Science, UCSB, Santa Barbara, CA 93106, (3) Geological Sciences, University of North Carolina-Chapel Hill, CB#3315, Chapel Hill, NC 27599, (4) Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964
Buried U-shaped troughs as much as 20 km-wide and flat-topped ridges adjacent to western Marie Byrd Land have recently been proposed as the result of late Oligocene West Antarctic glaciation. Here, additional evidence for pre-25 Ma glaciation is presented for the southeast Ross Sea, together with a different stratigraphic correlation path that establishes age constraints. Rough Oligocene buried glacial topography contrasts with a buried smooth and planar middle Miocene “Red” angular unconformity. The Red unconformity extends east-west 160 km near the ice shelf edge, and is 700 m-deep. Part of a 2 km section of Oligocene to middle Miocene strata was removed by erosion. Any smooth post-rift subsidence profile requires that the Red unconformity was carved in water depths of several hundred meters. Several major early through Middle Miocene sequence boundaries merge to form this unconformity, suggesting multiple advances of thick grounded ice.