Iceberg ploughmarks and associated sediment ridges on the southern Weddell Sea margin

Ploughing by deep keels of floating icebergs is a common feature of high-latitude continental margins. Icebergs that have calved from glaciers or ice sheets produce a range of seafloor signatures, including linear to curvilinear grooves, rounded pits and ploughmarks terminating in sediment ridges. The dimensions and patterns of iceberg ploughmarks vary with iceberg size, water depth, local current, tide and wind conditions, seafloor sediment and past glacial history. The outer shelf and upper continental slope of the southern Weddell Sea is extensively ploughed by icebergs, and three different types of iceberg ploughmarks are recognized. The first signature is small grounding pits which occur over a wide area of the upper slope to water depths of c. 720 m (white arrow in Fig. 1a). The grounding pits have a mean depth of 8 m and a mean diameter of 280 m. The pits appear to be distributed randomly, with the highest intensity occurring in water depths of 410–670 m.