The insular margin of Iceland has been surficially formed by glacial action which beveled existing strata and then deposited morainal debris on the erosional surface. The Outer Insular Shelf (OIS) has prograded out to 30 km beyond the previous paleoshelf level. In an area 30 to 50 km from the mid-Atlantic Ridge axis through the Iceland margin, the shelf has been upwarped since the Late Pleistocene. Snaefellsnes Arch comprises the coalesced bases of former volcanoes southwest of Snaefellsnes Peninsula. Oblique to the mid-oceanic ridge axis are basement scarps beneath the Insular Margin that have trapped sediment. Basement seems to be highly reflective volcanogenic material over sediment in many areas. Marginal plateaus on the lower slope have entrained sedimentladen bottom water currents on the rise. Contourite deposits west-southwest of Iceland are delineated as Snorri Mid-Ocean Drift.