Where the keels of icebergs and sea ice touch the seafloor, deformation and reworking of the sedimentary substrate may take place. Point impacts produce pits in the seafloor, whereas continuing ice drift results in the formation of linear to curvilinear depressions referred to as ploughmarks, furrows or scours (Woodworth-Lynas et al. 1991). Sea-ice keels only exceptionally exceed about 20 m below water, where pressure-ridging takes place. By contrast, the keels of icebergs can range from tens of metres for small irregular bergs produced from grounded tidewater glaciers to over 500 m where calving takes place from major ice-sheet outlet glaciers (Barnes & Lien 1988; Dowdeswell et al. 1993; Dowdeswell & Bamber 2007). The presence of large iceberg ploughmarks in the geological record therefore indicates that ice was present at sea level to release icebergs into the adjacent ocean waters. Three-dimensional (3D) seismic data are, however, required in order to identify these features on buried shelf surfaces (Fig. 1).