Submarine push moraine formation during the early Fennoscandian Ice Sheet deglaciation

The glacial history in the topographically confined palco-ice stream drainage route of Vestfjorden, North Nor-way, was analysed based on bathymetric data, high-resolution seismology and C-14 AMS-dated gravity cores. The inner part of the fjord is characterised by axial-parallel megascale lineations wheras the outer part is dominated by two marginal morainal bank systems. The Vaeroy (inner) and Rost (outer) marginal moraine systems comprise several transverse, zigzag-shaped ridges. Seismic records show thrusted and folded sediment blocks within the ridges. The landforms are inferred to reflect basal processes and the transition from warm-based (inner fjord) to cold-based (outer fjord) conditions, i.e. fast flow followed by basal freeze-on, sediment deformation and morainal bank formation. The moraines formed during the final part of two palco-ice sheet re-advances. C-14 AMS dating indicates a maximum age of 13.7 C-14 ka BP (16.2 cal ka BP) for the Rost system whereas the Vaeroy system is inferred to be slightly older than 12.5 C-14 ka BP (14.5 cal ka BP). This demonstrates that the northern part of the Fennoscandian Ice Sheet behaved in a much more dynamic way during the early deglaciation than previously assumed. (c) 2007 University cf Washington. All rights reserved.