a broad depression in the ocean floor in the southern part of the Southern Ocean, between the continental slope of Antarctica, the South Georgia Rise, the Atlantic-Indian Rise, and the Kerguelen-Gaussberg Ridge. It extends 6,200 km along 60° S lat. and is 1,500 km wide. The greatest depths are 6,709 and 6,972 m. The basin is a Mesocenozoic downwarp of the ocean floor with a sedimentary cover 600–700 m thick. The bottom is composed of deepwater red clays and diatomaceous mud.