Submarine landforms and the reconstruction of fast-flowing ice streams within a large Quaternary ice sheet:: The 2500-km-long Norwegian-Svalbard margin (57°-80°N)

Morphological interpretation of regional and detailed bathymetric data sets on the 2500-km-long Norwegian shelf from the North Sea (57 degrees N) to Svalbard (80 degrees N) has revealed a dynamic ice-flow pattern along the western margin of the Scandinavian and Barents/Svalbard ice sheets. About 20 cross-shelf troughs with megascale glacial lineations (MSGL; elongate ridges and grooves oriented parallel to trough long axes) are interpreted as former pathways for fast-flowing ice streams. Studies of large-scale margin morphology and seismic profiles have identified large submarine fans at the mouths of several major cross-shelf troughs. Less dynamic ice probably existed on shallower banks. The two largest paleo-ice streams were the Norwegian Channel Ice Stream and Bear Island Trough Ice Stream, each 150-200 km wide at the mouth. The lengths of individual MSGL vary from hundreds of meters to several tens of kilometers, and the distance between ridges varies from 0.1 to 3 km. MSGL amplitudes reach 15 m, but are commonly < 10 m. The onset of MSGL and, hence, fast ice flow is generally close to the outer coast, at the border zone between crystalline rocks and softer sedimentary rocks. Transverse submarine ridges on various scales, commonly parallel to the shelf edge, reflect either the maximum ice-sheet position or the recessional pattern of the ice sheet. Lateral ice-stream moraines several tens of kilometers long have also been mapped along the sides of several cross-shelf troughs, identifying the border zone between fast ice flow and stagnant or slow-flowing ice on intervening banks.