The Eocambrian glaciation in Norway |
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| Authors: | Prof Dr Nils Spjeldnaes |
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| Institution: | (1) Oslo;(2) Present address: Geologisk Institut, Universitet, Aarhus C, Denmark |
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| Abstract: | Summary Traces of the Eocambrian glaciation are found in three district in Norwegian territory, 1) in the south-east, at and north of the lake MjØsa, 2) in north-east, in Finnmark, and 3) in Spitzbergen. The two first districts are connected by a number of localities in Sweden, along the margin of the Caledonian Mountain chain. The glacial beds form the base of the Eocambrian, which is taken as the lowest part of the Cambrian. They generally rests with a more or less pronounced disconformity on dolomitic rocks of the Esmarkian (the upper part of the Riphean system). In some cases they rest directly on the crystalline Precambrian basement. This is due either to Esmarkian tectonic movements, to deep glacial erosion or both. The glacial beds are varied lithologically, but the characteristic rock types are tillites, boulder-shales and varved mudtones. All tillites are not regarded as fossil moraines, formed by ice movement. Some of them are supposed to have been formed by dropping of material from floating ice, either glacier ice or sea ice in a marine or brackish environment. The wide and uniform distribution of the tillite seems to preclude an interpretation as mudflows. Comparison with the Quaternary glacial sediments have given interesting results, and add to the evidence for a glacial origin of the tillites. It is also indicated that the direction of transport will depend on whether the material was rafted with glacial ice, or with drifting sea ice. Much more work has to be done both on the sedimentology, stratigraphy and paleomagnetism of the Norwegian Eocambrian glacial deposits and comparable sediments in order to get a clear and coherent picture of the glaciation, but the present evidence seem to indicate that it was part of a world-wide glaciation of even greater extent than the Permo-Carboniferous and Quarternary ones. |
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