New Mexico Geochronology Research Laboratory, Socorro

Because of the paucity of exposed rock the direct physical record of Antarctic Cenozoic glacial history has become known only recently and then largely from off-shore shelf basins through seismic surveys and drilling. The number of holes has been small and largely confined to three areas (McMurdo Sound, Prydz Bay and Antarctic Peninsula), but even in McMurdo Sound, where Oligocene and early Miocene strata are well-cored, the Late Cenozoic is poorly known and dated. The latest Antarctic geological drilling program, ANDRILL, successfully cored a 1285m-long record of climate history spanning the last 13 m.y. from sub-sea floor sediment beneath the McMurdo Ice Shelf (MIS), using drilling systems specially developed for operating through ice shelves. The cores provide the most complete Antarctic record to date of ice sheet and climate fluctuations for this period of Earth’s history. The >60 cycles of advance and retreat of the grounded ice margin preserved in the AND¬1B record the evolution of the Antarctic ice sheet since a profound global cooling step in deep sea oxygen isotope records ~14 m.y. ago. A feature of particular interest is a ~90m-thick interval of diatomite deposited during the warm Pliocene, and representing an extended period (~200,000 years) of locally open water, high phytoplankton productivity and retreat of the glaciers on land.