GLACIAL SEQUENCE STRATIGRAPHY OF THE ANDRILL AND-1B CORE, ANTARCTICA

A single 1284.87m-long drill core (AND-1B) was recovered using the McMurdo Ice Shelf, Antarctica as a drilling platform. The Neogene (~0-10 Ma) core includes glacimarine, terrigenous, biogenic and volcanic sediment that provides new knowledge on the Late Neogene behavior and variability of the Ross Ice Shelf (RIS) and the West Antarctic Ice Sheet (WAIS), and their influence on global climate, sea-level and ocean circulation. Repetitive vertical successions of facies representing successively subglacial, ice proximal and ice distal open marine environments, imply at least 60 fluctuations of WAIS. These have been grouped into 4 types of facies cycles or motifs that correspond to glacial-interglacial variability during climatically distinct periods of the Late Neogene: (1) Cold polar climate and ice (Late Miocene, ~13-10Ma & Pleistocene, ~1-0Ma). (2) Relatively warmer climate, polythermal ice and interglacials dominated by pelagic diatomites (Pliocene, ~5-2Ma). (3) Warmer climate, polythermal ice with interglacials dominated by hemipelagites (early-Late Miocene, ~9-6Ma). These facies successions representing full glacial advance and retreat cycles, combined with distinctive surfaces (e.g., glacial advance, erosion, retreat and minimum) are used to prescribe models for deepwater (well below wave-base) Glacimarine Sequences on continental shelves used for sequence stratigraphic analysis of glacial successions similar to that established by Powell and Cooper (2002) for temperate regimes. Facies types and proportions vary amongst glacial regimes and are distinctive proxies for broad paleoclimatic inferences. Preservation of particular facies above or below key surfaces document relative magnitudes and longevity of ice sheet advances and relative rates of ice sheet retreats. A critical combination of local sediment accumulation rates combined with tectonic subsidence is required to preserve such successions. The models are generalized so as to be useful for inferring paleo-glacial and paleoclimatic conditions from the ancient stratigraphic record.

Powell, R.D. and Cooper, J.M., 2002. A sequence stratigraphic model for temperate, glaciated continental shelves. Geol. Soc. London, Spec. Pub. 203: 215-244.