A new depositional model for ice shelves, based upon sediment cores from the Ross Sea and the MaC. Robertson shelf, Antarctica

Abstract

We document the similarity of depositional facies occurring in gravity cores recovered from two disjunct regions of the Antarctic continental shelf: the Ross Sea and the MaC. Robertson shelf. The facies sequence model is represented in two cores, one collected during the 1995-1 cruise of the R/VNathaniel R. Palmer(core NBP95 TC-18) and the other collected by the RSVAurora Australisduring cruise 149 in 1995 (core 149 39GC38). Both cores show a succession of facies indicative of ice-shelf retreat during the late-Pleistocene to Holocene transition. Distinct lithofacies range in thickness from a few tens of cm to 1 m and consist of (from bottom to top) a coarse, granulated sandy mud; laminated silt and clay; structureless silly clay; poorly sorted sandy siliceous mud; and siliceous mud and ooze. These facies represent the passage of distinct depositional regimes across the core sites, including sub-ice shelf beneath a basal debris zone; sub-ice shell distal to a debris zone; calving-line transition; and open marine. This facies model represents an advance in our understanding of Glacial marine stratigraphy for the Antarctic continental shelf and will provide the basis for more realistic palaeoglacial reconstructions.