Piston-core based biostratigraphic constraints on Pleistocene oscillations of the West Antarctic Ice Sheet in western Ross Sea between North Basin and AND-1B drill site

New diatom-biostratigraphic age data derived from piston core were used to constrain the chronology for a seismic-based interpretation of West Antarctic Ice Sheet (WAIS) advance and retreat from the North Basin outer shelf in western Ross Sea. The data demonstrates that grounded ice occupied the outer shelf on at least ten occasions during the last 2.0 Ma of the Pleistocene. Although the biostratigraphic resolution is low, the constraints permit correlations to coeval section recently drilled in South McMurdo Sound at the AND-1B drill site. Our interpretation of regional-scale correlations suggests that the Pleistocene dynamics of the WAIS involved grounding-line translations in excess of 600 km. However, the data also suggests that only two major advances of grounded ice occurred since similar to 0.71 Ma. In other words, several of the late Pleistocene sediment cycles at AND-1B must represent only minor advance and retreat of grounded ice to and from South McMurdo Sound. The results prove false the long-standing tacit assumption that the WAIS experienced major advances in association with peak glacials and eustatic lowstands during the last 700 ka of the Pleistocene. These results show that piston cores can be used to constrain the timing of pre-Holocene grounding events. These data also highlight the need for regional-scale correlations to distinguish between major versus minor grounding-line translations of grounded ice in the marine setting. (C) 2011 Elsevier B.V. All rights reserved.