Debris-flow deposits on the West Antarctic continental slope

Abstract

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). Fig. 1. 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). …