Unusual iceberg ploughmarks on the Norwegian continental shelf

Iceberg ploughmarks are produced when the keels of drifting icebergs impinge upon and cut into seafloor sediments. They are common landforms of high-latitude shelves and fjords, especially in water shallower than about 500 m where they are easily detected using modern multibeam echo-sounding and earlier side-scan sonar systems (e.g. Lien 1983; Dowdeswell et al. 1993). In addition, similar buried morphological features have been imaged within Quaternary sediments on palaeo-shelves using 3D seismic methods (e.g. Dowdeswell & Ottesen 2013). Five examples of unusual linear to curvilinear features from the seabed of the Norwegian continental shelf are presented (Fig. 1). The first and rather small feature is from outside Brasvellbreen (Fig. 1a), an outlet glacier of Austfonna in E Svalbard. The looped feature is about 15 m wide and 1 m deep and has small berms on either side. The diameter of the loop is about 1.2 km. The feature is found on top of a dense criss-crossing pattern of similar features on the seafloor in water depths of around 40 m. Fig. 1. Iceberg ploughmarks on the Norwegian continental shelf and upper slope (located in (g)). ( a ) An almost-circular iceberg ploughmark outside Brasvellbreen, Austfonna, Svalbard. ( b ) Peculiarly shaped iceberg ploughmark in the central Barents Sea. ( c ) Iceberg ploughmark demonstrating rotation, central Barents Sea. The many small round …