Late glacial landform associations at Jaeren (SW Norway) and their glaci-dynamic implications

The Jaeren lowland is located on the southwestern coast of Norway between a mountainous region in the east and the offshore Norwegian Channel in the west. During the Last Glacial Maximum, Jaeren was in an intermediate position between an ice stream following the Norwegian Channel northwards, and westward flowing inland ice. The dynamic behaviour of the inland ice and the interaction with the ice stream are examined by means of geomorphological analysis of digital terrain models and sedimentological investigations. SW-trending drumlins were formed at Jaeren below tributary ice from the inland, feeding into the Norwegian Channel Ice Stream. The presence of Rogen moraine in the central part of Jaeren indicates a frozen substratum prior to their formation, and this suggests a transition to cold-based ice between the tributaries. The deglaciation of the Norwegian Channel at about 15 ka BP resulted in an unstable ice front for the inland ice sheet. The formation of Rogen moraine may be explained by a dynamic advance resulting in extensional flow and fracturing of the frozen substratum between the tributaries. The dynamic advance was followed by an early deglaciation of the coastal areas as evidenced by shallow marine sediments. Deformation of the shallow marine sand indicates a glacial readvance through the valleys formerly acting as tributaries to the ice stream.