Arcuate moraines on the continental shelf NW of Ireland

Abstract

The geomorphological record of ice sheets on continental shelves includes a range of flow-transverse ridges that indicate the former position of the ice-sheet margin or grounding zone in time and space. On the continental shelf offshore of NW Ireland, well-developed arcuate sediment ridges are moraines that record the lobate retreat of a grounded Irish Ice Sheet from the shelf edge during the last deglaciation (Fig. 1). Retreat across the shelf was episodic and punctuated by occasional minor readvances or oscillations of the ice-sheet margin. Fig. 1. Moraines on the continental shelf off NW Ireland. ( a ) Multibeam image showing the NE–SW-aligned arcuate moraines. Acquisition system Kongsberg Simrad EM1002 and EM3002. Frequency 95 and 300 kHz. Grid-cell size 20 m. ( b ) Enlarged image of the NE–SW-aligned arcuate moraines on the mid-shelf and the prominent moraine at the mouth of Donegal Bay. ( c ) Oblique view of the large moraine looking northwards (about 12 km across the bottom). VE×15. Grid-cell size 20 m. ( d ) Sub-bottom profile (x′–x) across the large moraine. Note asymmetrical eastern slope. ( e ) Cross-section (y′–y) of the nested moraines. VE×6. ( f ) Location of study area (red box; map from IBCAO v. 3.0). The continental …