Evidence of ice movement over southwest Norway indicating an ice dome over the coastal district of west Norway

Abstract

Records of several directions of ice movements occur in southwestern Norway. The oldest movement (Phase A) was towards NW and may be of Early Weichselian age or older. The Phase B ice moved towards S-SE, Phase C again towards NW, Phase D towards SW, Phase E was a local movement towards S, and Phase F is the Younger Dryas glacial movement. The Phase B ice flow markers most likely reflect a regional glacial phase. The emphasis is placed on a discussion of the age and palaeoglaciological implications of Phase B. One possible correlation is that Phase B corresponds to the ‘Jæren Stadial’ till, underlying the 40,000–30,000 BP ‘Sandnes Interstadial Clay’, at Jæren. Phase B ice flow markers further match the fabric of a till of supposed Early to Middle Weichselian age, southwesternmost coast of Norway. This till is deposited from NNW. Phase B suggests an ice sheet either based on the continental shelf in the North Sea, or it suggests an ice dome over the coastal district of west Norway. In the former case, evidence of a North Sea based ice should be expected around and in the North Sea. In the latter case, which is considered being the most likely one, it may explain the problematic occurrence of the ‘Sandnes Interstadial Clay’ up to very high altitudes at Jæren. The only possible land-evidence of a North Sea centered ice-mass older than Late Weichselian maximum is found at Caithness, Scotland, which suggests a pre-40,000 ice sheet in the North Sea Basin (Sutherland, 1984; Sejrup et al., 1987). However, the lithology of the North Sea sediments does not seem to show any till-like deposit between Late Weichselian maximum and 130–200 ka (Sejrup et al., 1987). The consolidating-value of pre-Late Weichselian North Sea sediments does not exceed 4000 kN/m 2, while a P′ C-value of about 15,000 kN/m 2 should be expected if the ice thickness was about 1500 m. However, sediments will not be compressed unless: (1) they are unfrozen, and (2) the pore water can escape. Coastal ice domes may have occurred both at the onset and final stage of glaciations.