The role of grounding-line sediment supply in ice-sheet advances and growth on continental shelves: an example from the mid-Norwegian sector of the Fennoscandian ice sheet during the Saalian and Weichselian

Abstract

We discuss the consequence of sediment accumulation at the grounding line of glaciers advancing across continental shelves. Sediment transfer through a deformable till bed and deposition at the grounding line act to decrease the water depth and adds support to the termini. Both are mechanisms that act to lower the calving rate and hence reduce mass losses during an advance of a grounded glacier. We use the geological record of the Saalian and Weichselian advances of the Fennoscandian ice sheet across the mid-Norwegian continental shelf to elucidate the consequence of this process. Based on seismic investigations and published maps, we infer that the development of a morainal bank fed and sustained through the advance(s) by means of a deformable bed was indeed important. This allowed the ice sheet to advance across a wide seaward dipping shelf, depositing thick diamicton (in places of more than 200 m thick) and a terminal morainal bank complex. We relate the reasons for this depositional mode, i.e. shelf and shelf edge accumulation rather than deposition of glacial debris flows on the continental slope, to slow and fast glacier flow regimes.