Ocean Drilling Program, United States

Leg 178 will drill eight sites off the Pacific margin of the Antarctic Peninsula to provide a high resolution record of Antarctic continental climate over the past 6-10 m.y., and a direct check on the presumed glacio-eustatic origin of global sea-level change over the same period. Moreover, it is an essential preliminary to the more difficult task of extracting the complete Cenozoic record of Antarctic glacial history by drilling the East Antarctic margin. The glacial prograded wedges of the Antarctic Peninsula margin are particularly well developed, and their glacial record is well preserved because of the margin's tectonic youth, high snowfall, small reservoir proximal glacial regime, and underlying 2-D geometry. Associated terrigenous hemipelagic drifts on the adjacent continental rise contain a continuous, high-resolution record of continental climate that will act as a reference section for the topset and foreset records of the shelf. International collaboration through the Antarctic Offshore Acoustic Stratigraphy initiative has made extensive data sets available for the planning of a drilling campaign. Site locations strike a balance between the greater density and diversity of data in the northeast and the greater time separation between tectonic and glacial control of sedimentation in the southwest. The sites aim to sample glacial sedimentation over the past 10 m.y. in three related depositional environments (shelf topsets and foresets and rise drifts). This conservative, overlapping sampling strategy allows comparison of depositional environments before attempting to investigate the longer and more complex history of East Antarctic glaciation. Drilling in Palmer Deep, a glacially overdeepened basin on the inner shelf, will sample an expanded Holocene section. Paleoproductivity in Palmer Deep seems representative of regional climate, so this section can be used to compare decadal- and millennial-scale regional climate variability with that of low-latitude regions and with that recorded in ice cores.