Substrate control on distribution of subglacial and glaciomarine seismic facies based on stochastic models of glacial seismic facies deposition on the Ross Sea continental margin, Antarctica

A quantitative approach was utilized to establish the nature of spatial and temporal variations of glaciomarine and subglacial seismic facies deposition in the Ross Sea. The Ross Sea is an excellent area to study Antarctic ice sheet volume variations because it receives ice sheet drainage from approximately 25% of the continent and it contains subsiding basins to preserve the stratigraphic record of the ice sheet volume fluctuations. This region receives most of the influence on deposition from the marine-based West Antarctic Ice Sheet which is believed to have been subject to catastrophic surges [Hollin, J.T., 1962. On the glacial history of Antarctica. Journal of Glaciology, 4: 173-195]. The Eastern Basin, in particular, has been subsiding, creating accommodation space in which to preserve the Plio-Pleistocene record of ice sheet fluctuations. Evidence from high-resolution seismic data in conjunction with DSDP Leg 28 drilling results are used to test hypotheses of paleo-ice sheet behavior. Here we present quantitative evidence for a dynamic polar style of glaciation (meaning that the ice sheets have had 'dynamic' or large ice volume change), not merely in the Plio-Pleistocene, but back to the Late Oligocene. High-resolution seismic data correlated to DSDP Sites 270-273 shows evidence of multiple ice sheet grounding events in central and eastern Ross Sea strata, a recipient of both West and East Antarctic Ice Sheets, from the Late Oligocene until the present. We suggest that the West and East Antarctic Ice Sheets are dynamic and have gone through a full spectrum of thermal states (temperate through polar) since the Late Oligocene and not necessarily in any particular preferred temporal order. Statistical analysis of the spatial distribution of seismic facies within 'seismic cores' indicates that tectonic, influence on distribution of basal substrate is a significant contributor to spatial variability of subglacial depositional processes and therefore distribution of subglacial facies. (C) 1997 Elsevier Science B.V.