Birger Larsen

Forty million years of Antarctic glacial history yielded by Leg 119 of the Ocean Drilling Program

During Leg 119 of the Ocean Drilling Program, between December 1987 and February 1988, six holes were drilled in the Kerguelen Plateau, southern Indian Ocean, and five in Prydz Bay at the mouth of the Amery Ice Shelf, on the East Antarctic continental shelf. The Prydz Bay holes, reported here, form a transect from the inner shelf to the continental slope, recording a prograding sequence of possible Late Paleozoic to Eocene continental sediments of fluvial aspect, followed by several hundred metres of Early Oligocene (possibly Middle Eocene) to Quaternary glaciallydominated sediments. This extends the known onset of large-scale glaciation of Antarctica back to about 36–40 million years ago, the sedimentary record suggesting that a fully developed East Antarctic Ice Sheet reached the coast at Prydz Bay at this time, and was more extensive than the present sheet. Subsequent glacial history is complex, with the bulk of sedimentation in the outer shelf taking place close to the grounding line of an extended Amery Ice S helf. However, breaks in the record and intervals of no recovery may hide evidence of periods of glacial retreat.