Dating the Drake Passage

Science  21 Apr 2006:
Vol. 312, Issue 5772, pp. 333
DOI: 10.1126/science.312.5772.333f

The opening of the Drake Passage, between the southernmost tip of South America and the Antarctic Peninsula, was an essential step in the development of the Antarctic Circumpolar Current. However, estimates of the age of the passage range from as early as 49 million years to as late as 17 million years ago, so it has been difficult to assess what role the opening played in climate change. Scher and Martin (p. 428; see the news story by Kerr) present a marine sedimentary record of ocean circulation derived from Nd isotopes in fish teeth found downstream from the Drake Passage for the interval between 46 and 33 million years ago. They find that the passage must have begun to open 41 million years ago, in the middle Eocene. This event long preceded the opening of the last remaining corridor, the Tasmanian Gateway, around 35 million years ago, and major ice sheet growth in Antarctica, which began around 34 million years ago.

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