ANDRILL: STRATIGRAPHIC DRILLING FOR THE CLIMATIC AND TECTONIC HISTORY OF ANTARCTICA

ANDRILL is a multinational initiative with objectives to recover stratigraphic core records to use to interpret Antarctica’s climatic, glacial and tectonic history over the past 50 million years. A key motivation for ANDRILL is that the role of the Antarctic cryosphere in the evolution of the global climate system is poorly known. Understanding the history of Antarctic ice volume variation is critical for proper assessment of cryospheric interactions with the ocean, atmosphere and biosphere.

Limited exposures of Cenozoic strata in Antarctica (due to ice cover) and the low number of stratigraphic drillholes on the continental margin has forced geoscientists to interpret ice sheet history from information derived from lower latitude proxy records. Leading paradigms have been driven by the oxygen isotope record from deep-sea cores and eustatic changes from sequence stratigraphic records on passive continental margins. Interpretations based on these proxy records have little direct confirmation from geologic records in Antarctica. Sedimentary archives that were recently recovered by the Cape Roberts Project prove that high-quality proximal records of past ice sheet behavior are obtainable. Unfortunately such records are few in number. ANDRILL proposes to drill a portfolio of sites in McMurdo Sound to recover new sections of Cenozoic strata from locations proximal to the ice sheet that are ideally suited to record and date ice sheet oscillations, and associated oceanic and climatic variations.

Major aims of the McMurdo Sound Portfolio are: 1) to determine the fundamental behavior of the Antarctic cryospheric system (ice sheet, ice shelf, and sea-ice), including the magnitude and frequency of its changes on 10²-10⁶ year time-scales; 2) to obtain geological records from critical intervals in the development of the Antarctic cryosphere and integrate these records into glacial, climate and oceanic models; 3) to document the evolution and timing of major Antarctic rift and tectonic systems and the development of associated sedimentary basins; 4) to investigate the origins and adaptations of polar biota and 5) to determine the role of the Antarctic cryosphere on long- and short-order Cenozoic climate change, particularly in modulating thermohaline ocean circulation and changing sea-level elevation.