Erosion and deposition on migrating shoreface-attached ridges, Sable island, eastern Canada

The shoreface-attached ridges present along the south side of Sable Island, Nova Scotia, are the largest and deepest yet described, but become smaller and finer grained to the east because of decreasing energy levels. Strong, alongshore, storm currents cause them to migrate eastward at rates that may reach 50 m.a(-1). Their migrating troughs erode underlying sediments, modifying the wave-ravinement surface and creating shoreline-oblique depressions up to 12 m deep. Deposition occurs on their fee side, in the form of gently dipping, graded storm beds up to 1.2 m thick containing both high-angle cross bedding and hummocky cross-stratification. Overall, the ridge deposits coarsen upward and resemble shoreface successions. Obliquely onshore, cross-ridge flow causes upbuilding by the Huthnance process and accounts for the unusually high angle (similar to 50 degrees) between the ridges and the shoreface.