Shelf Break and Slope [24] The shelf break is characterized by a sharp change in gradient between the continental shelf and slope. In the Gulf of Papua the shelf break occurs between 135–140 m (Figure 3b). The Gulf of Papua shelf break is characterized by two distinct morphologies. Francis et al. [2008] docu- ment a highly linear shelf-edge barrier feature along the northern Ashmore Trough (Figure 3e). Sampling of the shelf-edge barrier has revealed the presence of a relict barrier reef system that occupied the ridge during the transgression [Tcherepanov et al., 2008]. [25] Elsewhere the shelf break is scalloped and/or incised by northwest-southeast trending submarine canyons. This is most evident in the southern shelf of the Pandora Trough region (Figure 3f). Francis et al. [2008] interpret the scalloped shelf break to be indicative of mass wasting with the channels acting as conduits for sediment gravity flows. Figure 3f indicates the location of a mass flow dep