Ocean Drilling Program, United States

The main objectives of our proposed drilling campaign in the Prydz Bay region are to: 1. Date the earliest evidence of glacial activity in Prydz Bay and obtain evidence on the Paleogene environment of Antarctica. 2. Link events in the East Antarctic Ice Sheet with changes in the Southern Ocean by drilling Oligocene and younger sediments beneath the continental rise that are distal counterparts of sediments beneath the Prydz Bay continental shelf and slope. 3. Recover a record of late Miocene and younger ice advances and interglacial periods from the Antarctic continental slope by coring sequences in the trough mouth fan built by advances of the Lambert Glacier-Amery Ice Shelf. Three primary drilling sites and alternatives have been identified to achieve these objectives. The drilling strategy consists of the following: 1. Drill one primary site (Site PBS-2A) on the Prydz Bay continental shelf to core the stratigraphic interval between the deepest Paleogene glacial sediments recovered at Ocean Drilling Program (ODP) Site 742 and the shallowest Cretaceous coal-bearing sediments acquired at ODP Site 741 to date the onset of glaciation in Prydz Bay and assess late Mesozoic and early Cenozoic preglacial environments. 2. Drill one primary site (Site PDB-12B) on the continental rise to sample a section of drift deposits and underlying units that extend back to the earliest time (early Oligocene) when ice reached the continental shelf edge and caused a major change in sedimentation on the rise. Glacial events recorded here will be compared with those seen in slope and shelf drill sites, including those drilled during Leg 119. 3. Drill one primary site (Site PBF-6A) on the continental slope to recover a section through the Prydz Channel Fan that was built by sediment carried in the base of the Lambert Glacier when it advanced to the shelf. Cores from this site should record the number of times the East Antarctic Ice Sheet has expanded to the shelf edge since late Miocene time. Alternative drilling strategies have been developed to fulfill the Leg 188 objectives in case ice conditions prevent access to preferred drilling areas. If time permits, the leg will acquire a high resolution Holocene environmental record by coring a section of biosiliceous Holocene sediments on the Mac Robertson Shelf west of Prydz Bay. This section should have a resolution comparable to ice cores and similar sediments cored in Palmer Deep during Leg 178.