Provenance of Pleistocene sediments in the ANDRILL AND-1B drillcore: Clay and heavy mineral data

The cryosphere in the McMurdo Sound region has undergone significant modifications during the last 1 Ma. Consequently, the sedimentary sequences underlying the modern McMurdo Ice-Shelf provide geological data to reconstruct variations in transport and depositional mechanisms of terrigenous material due to variations in ice sheet extension, grounding line position and main ice-stream flow directions during glacial and interglacial periods. The present study aims to investigate the clay and heavy mineral assemblages of the late Pleistocene subglacial and glaciomarine sediments recovered during the ANDRILL-McMurdo Ice Shelf Project in Windless Bight (South of Ross Island). The analyses show that the sediments are a mix of detritus from the McMurdo Volcanic Group (MVG) and the Transantarctic Mountains (TAM) from the south and west. MVG-derived minerals prevail with respect to TAM-derived minerals. The down-core mineralogical variations are determined by changes in the source rocks and the sedimentary processes. Sediments at the drill site are nourished by ice coming from the South which delivered rocks from the McMurdo Volcanic region; the enrichment of a TAM component in massive diamictites testifies that the ice sheet collected debris from the Transantarctic Mountains. When open marine conditions prevailed, only sediments from a local source (i.e. McMurdo volcanics) were deposited.