Clast provenance and variability in MIS (AND-1B) core and their implications for the paleoclimatic evolution recorded in the Windless Bight- southern McMurdo Sound area (Antarctica)

Summary Granule- to cobble-grade clasts in the uppermost 575 m of the MIS drill-core (AND-1B) highlight significant downcore modal and compositional variations, which provide direct information about the potential source regions and evidence of an evolving provenance, most likely as results of variable ice conditions and ice-flow directions during the deposition of recovered diamictites. In addition to a significant contribution from the McMurdo Volcanic Group, the dataset indicates a compositionally varied clast assemblage including several basement rock types which are comparable to the main geological units exposed in the area SW of the drillsite, between the Skelton and Byrd Glaciers. Based on these provenance inferences and sedimentological constraints, the deposition of the diamictite units in the upper 575 m section recovered by the AND-1B drillcore would imply several oscillations of a grounded Ross Ice Shelf, possibly coupled with major phases of expansion of the West Antarctic Ice Sheet