Grounding-zone wedges on Antarctic continental shelves

Abstract

The concept of sediment accumulation at high rates in ice-stream grounding-zone settings originates with Alley et al. (1987) who envisioned ‘grounding zone deltas’ composed of sediment transported in a thin deformation-till layer beneath ice streams. This led to the discovery of sediment accumulations on Antarctic continental shelves that, in some instances, revealed foreset beds in seismic sections (e.g. Bart & Anderson 1995). Subsequently, with the advent of multibeam swath bathymetry, these wedges were identified in a number of shelf areas and the term grounding-zone wedge (GZW) was adopted (Shipp & Anderson 1997). Seismic images of GZWs show that they are wedge-shaped in a direction parallel to cross-shelf trough axes, tapering in a landward direction (Fig. 1) and lens-shaped in a transverse direction (Shipp et al. 1999; Howat & Domack 2003). GZWs typically range in thickness from a few metres to a few tens of metres and are occasionally stacked in a back-stepping …