Department of Geology and Environmental Geosciences, Northern Illinois University, DeKalb, IL, USA

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 offshore shelf basins through seismic surveys and drilling. The number of holes on the continental shelf 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 1285-m-long record of climate history spanning the last 13 m.y. from subsea-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.a. A feature of particular interest is a ~90-m-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.

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.

The ANDRILL Program successfully recovered a 1285 m-long succession of cyclic glacimarine sediment with interbedded volcanic deposits in its first season of drilling from the McMurdo Ice Shelf (MIS). The MIS AND-1B drill core represents the longest and most complete (98% recovery) geological record from the Antarctic continental margin to date, and will provide a key reference record of climate and ice-sheet variability through the Late Neogene. Here we present a synopsis of this Initial Science Report with emphasis on the potential of the record for improving our knowledge of Antarctica’s influence on global climate.

This section reports preliminary data and results on petrology and geochemistry of AND-1B core