ドレーク海峡
The Tasman Gateway between Australia and Antarctica began to open . Palaeontological evidences indicate the Antarctic Circumpolar Current (ACC) was established in the Late Oligocene with the full opening of the Drake Passage and the deepening of the Tasman Gateway. The oldest oceanic crust in the Drake Passage, however, is -old which indicates spreading between the Antarctic and South American plates began near the Eocene/Oligocene boundary.