Paraglacial landscapes in St George's Bay, Newfoundland, Canada

Abstract

The Late Wisconsinan submarine moraine in St George's Bay, Newfoundland, was exposed to erosional processes during and after an early Holocene −25 m lowstand of relative sea level. Primary morphology has been largely removed, resulting in a gently sloping platform veneered with mobile sand and gravel, terminating on the landward side in progradational ‘spillover’ lobes. Erosion of coastal Quaternary deposits has produced systems of gravel-dominated spits and barriers constructed upon subaqueous platforms that have buried glacimarine deposits and a lowstand delta. Paraglacial processes have therefore created a complex submarine terrain with few parallels in Atlantic Canada. A gently sloping platform-like shoal (average depth 20 m) extends across inner St George's Bay (Fig. 1a), enclosing several basins to the east (maximum depth 100 m). The platform surface comprises sand waves, areas of gravel ripples and patches of immobile, bouldery gravel with relief of 2–3 m (e.g. A in Fig. 1a). This mosaic of terrains is reflected in a backscatter image (Fig. 1b). As a result of wave action, sand and gravel have migrated to the NE, spilling into the adjacent basins to form lobate, prograding sediment wedges (e.g. B in …