Large-scale development of the mid-Norwegian margin during the last 3 million years

Abstract

During the last c. 2.7 My, large quantities of glacially derived material were transported westwards from the Norwegian mainland areas and inner shelf and deposited mainly as prograding sediment wedges into a basin of intermediate depth offshore Mid Norway. The deposits are more than 1000 m thick in extensive areas, and are defined as the Naust Formation. In the Haltenbanken–Trænabanken region, the shelf edge migrated 100–150 km westwards. The narrow Møre shelf was built out only in the order of 30–50 km, mainly due to a steeper pre-existing slope dipping towards a much deeper basin. In this area, the Holocene Storegga Slide, as well as older slides, displaced slope sediments towards the deeper part of the basin. In Early Naust time, the most extensive progradation occurred in the northern area, possibly due to the combined effect of land uplift and glaciations. The importance of glaciations for the progradation of the Møre shelf and areas farther south increased through the Pleistocene period. The Norwegian Channel Ice Stream became very important during the last three glaciations, and a thick succession of glacigenic debris flows was deposited on the North Sea Fan. More than 400 m of sediments accumulated during the Weichselian. All the last three glaciations supplied glacial debris beyond the shelf edge. The most extensive progradation in the north was in the Skjoldryggen region, particularly during the Elsterian glaciation. During ‘ice-free’ periods, hemipelagic and contouritic sediments were deposited on the slope. Such sediments are most common in the Storegga Slide area, where they hosted glide planes beneath the major slides.