Ice-sheet dynamics and glacial development of the Norwegian continental margin during the last 3 million years

Abstract

This thesis is mainly about the dynamics of the palaeo-ice sheets that covered Scandinavia, Barents Sea and Svalbard during the last glaciation. Morphological interpretation of regional and detailed bathymetric data sets on the Norwegian shelf from the North Sea (57°N) to Svalbard (80°N) has elucidated the ice-flow patterns along the western margin of the Scandinavian and Barents/Svalbard ice sheets. About 20 cross-shelf troughs with glacial lineations are interpreted as former pathways for fast-flowing ice streams. The two largest palaeo-ice streams were the Norwegian Channel Ice Stream and Bear Island Ice Stream, each 150-200 km wide at their mouths. Studies of large-scale margin morphology and seismic-reflection profiles have identified large submarine fans at the mouths of several major cross-shelf troughs. Improved knowledge of the regional development of the margin, and detailed morphological maps of the buried palaeo-surfaces, show that similar large-scale glacial processes have been active in a substantial part of the Late Pliocene/Pleistocene (c. last 3 million years). Interpretation of a large seismic data base has made it possible to map the whole Naust Formation, which comprises sediments deposited on the mid-Norwegian margin during the last 3 million years. During this period, large quantities of glacially derived material were transported westward from the Norwegian mainland and the inner parts of the shelf, and deposited mainly as prograding sediment wedges into a basin of intermediate depth offshore of Mid Norway. The deposits are more than 1000 m thick over an extensive area, and the shelf edge migrated up to 150 km westwards. Very-high-resolution bathymetric data has made it possible to study sedimentary processes related to recently surging glaciers on Svalbard (the last few hundred years). The data sets also show that mega-scale glacial lineations not only can form beneath large ice streams, but are also produced over a few years beneath surging tidewater glaciers lying on deforming sedimentary beds.