Three-dimensional seismic data from the Barents Sea margin reveal evidence of past ice streams and their dynamics

Three-dimensional seismic data from the southern flank of the outer Bear Island Trough at the western Barents Sea margin show former ice-stream activity; the interpretation of such activity is based on megascale lineations and long chains of megablocks and rafts buried in thick till units between glacially eroded horizons. In several units the sediment blocks and rafts are aligned in chains up to 2 km wide and 50 km long. Individual megablocks have an areal extent of up to 2.2 km(2), and their internal structure is well preserved, providing information about the processes involved in their incorporation into the ice, subsequent detachment, and partial disintegration. Previous discussions of sub-ice-stream processes have focused on ductile deformation of weak sediments and molding of subglacial landforms. This work also demonstrates the importance of brittle sediment deformation in these settings, adding to the understanding of ice streams as agents of glacial erosion, transport, and sedimentation.