De Geer moraines on German Bank, southern Scotian Shelf of Atlantic Canada

Abstract

Numerous regularly spaced, parallel, linear to curvilinear ridges of sediment are recognized to form at or close to the grounding lines of water-terminating glaciers (Linden & Moller 2005). These ice-flow transverse ridges, sometimes known as De Geer moraines (De Geer 1889), have modest heights and widths and variable lengths. De Geer's original description of Swedish moraines with these characteristics invoked an annual cycle. Present use of ‘De Geer moraine’ refers to closely spaced subaqueous moraine ridges which may or may not be annual. The distribution and pattern of ubiquitous De Geer moraines on German Bank provide insight into the direction and timing of regional deglaciation of the southern Scotian Shelf (Todd et al. 2007). Across a bathymetric range of over 100 m, southern German Bank is mantled by swarms of ridges; each ridge displays a quasi-linear or curved line in planform (Fig. 1). In topographic depressions, the ridges are subdued in relief or are absent (Fig. 1a). The strike of the ridge crests is generally WSW–ENE. Individual ridges can be traced horizontally from short segments of a few hundred metres up to almost 10 km. …