Figure 18. Detailed multibeam-bathymetric image of boulders, many with obstacle marks, sand waves and megaripples, and trawl marks, in the southeast part of the study area. Although this area was mapped by Needell and Lewis (1984) as exposed coastal plain sediments, the presence of numerous boulders indicates that the underlying deposits are covered by at least a thin layer of winnowed basal till. Sand waves and megaripples with steep, westward-facing slip faces and asymmetry of obstacle marks around boulders indicate westward net sediment transport. Trawl marks caused by dragging fishing gear appear as grooves on the sea floor in the eastern part of the image. Location of image is shown in figure 13.