Most of the West Antarctic continental margin has prograded during Neogene and Quaternary times, due largely to sediment delivery to the shelf break by ice sheets (Larter & Cunningham 1993; Nitsche et al. 2000; Cooper et al. 2008). Continental slope progradation is widely attributed to debris-flow deposition, but geophysical data that show the morphology of individual debris-flow deposits are rare. Morphologically, the continental slope can be divided into low seafloor gradient (<3°) trough-mouth fans (TMFs), developed at the mouths of some large palaeo-ice streams, and inter-fan areas with steeper slopes. We describe acoustic sub-bottom profiles and a sediment core from debris-flow deposits on Belgica Fan (Dowdeswell et al. 2008) and a sub-bottom profile of a debris-flow deposit on an inter-fan area on the Amundsen Sea continental slope (Fig. 1a).
Acoustic profiles from the West Antarctic continental slope and photographs and x-radiographs of a sediment core from the Belgica Fan (Dowdeswell et al. 2008). (a) Location of study areas (red box and red-filled rhombus; map from IBCSO v. 1.0). (b) Oblique view from NNE of a new regional bathymetry compilation over outer Belgica Trough (BT) and Belgica Fan (BF), incorporating all available multibeam and single-beam bathymetry, with shaded-relief illumination from ENE. Grid-cell size c. 900 m. White lines labelled x–x′ and y–y′ show locations of (c) and (d), respectively, and white oval shows location of (e). …
