ODP Leg 188 abstract

Leg 188: Prydz Bay

The Antarctic ice sheet is a key component of the world's climatic system and has a major influence on global sea levels. To better understand its role and to test models of ice sheet behavior, ODP scheduled one leg in 1998 (Leg 178) and a second leg (Leg 188) for January-March, 2000 to drill the Antarctic. Leg 188 will address the ODP Long Range Plan theme of understanding Earth's changing climate by drilling Cenozoic sediments in Prydz Bay, Antarctica, and on the adjacent continental slope and rise known as the Cooperation Sea. Prydz Bay lies on the East Antarctic coastline between 68°E and 78°E. It is the downstream end of the Amery Ice Shelf-Lambert Glacier ice drainage system, which drains about 22% of the East Antarctic ice sheet. The Lambert Glacier responds to fluctuations of the interior of the East Antarctic ice sheet, which are then reflected in the sediments of Prydz Bay. Included in the drainage basin are the Gamburtsev Subglacial Highlands, which may have been the nucleus of the earliest Antarctic glaciation so that the Lambert Graben may contain the earliest Cenozoic glacial sediments. During Cenozoic glacial episodes, the Lambert Glacier advanced to the shelf edge, extending it by progradation and then building a large trough mouth fan that probably contains a relatively complete record of glacial history. Interglacial sediments are also probably preserved on it. Thus, the Prydz Channel Fan could contain the most complete record of glacial history of any sedimentary sequence on the East Antarctic margin. The continental rise adjacent to Prydz Bay exhibits large sediment drifts deposited under the influence of turbidity currents from the continental shelf and deep currents in the Southern Ocean. Seismic horizons can be mapped from the slope to the rise, allowing the relationships between slope and rise deposition to be determined. Drilling these sediment drifts can therefore give a picture of changes in paleoceanography that can be correlated with changes in the East Antarctic Ice Sheet and compliment the ODP database from other parts of the world. Prydz Bay and the adjacent Cooperation Sea can provide long term perspectives of Antarctic glaciation and paleoceanography that will compliment other circum-Antarctic drilling proposals. Such sections could provide a significant contribution to Initiative 1 of the Long Range Plan, understanding natural climate variability and rapid climate change.

Therefore the main objectives of our proposed drilling campaign in the Prydz Bay region are:

1. Link events in the East Antarctic Ice Sheet with changes in the Southern Ocean by drilling sediment drifts on the continental rise equivalent to the Prydz Bay continental slope, particularly the prograding sediments deposited by ice advances across the shelf.

2. Recover.a record of Plio-Pleistocene ice advances and interglacial deposits from the Antarctic continental slope by penetrating sequences in the trough mouth fan built by advances of the Lambert Glacier-Amery Ice Shelf.

3. Date the earliest evidence of glacial activity in Prydz Bay and obtain evidence on the Paleogene environment of Antarctica.

Staff Scientist: Carl Richter