S U M M A R YPalaeomagnetic and structural studies of the Dalsfjord Nappe, western Norway, show that the basal !ow-angle detachment (Dalsfjord Fault) is a long-lived fault zone, and that the most important phase of faulting was of Devonian extension, probably nucleated o n an earlier Silurian (Scandian) thrust. Fault rocks produced during subsequent movements indicate that t h e Dalsfjord Fault underwent periods of brittle low-angle extensional reactivation during the Permian (250-260 Ma) and Upper Jurassic/Lower Cretaceous (c. 150 Ma), corresponding with stages of major extensional movements on the continental shelf. Palaeomagnetic studies may be of great importance for dating faults and major movement stages in long-lived fault systems. T h e particular importance of t h e results is that they show that low-angle normal faults can operate in a brittle upper crustal regime.
The Kalak nappe complex of N Norway involves late Precambrian to Middle Cambrian sediments and a Precambrian gneiss basement on which the sediments were deposited. While the uppermost nappe in Finnmark was emplaced during the Silurian the members of the Kalak nappe complex were emplaced in late Cambrian/early Ordovician times during the Finnmarkian orogenic stage—probably the analogue of the Grampian stage of the British Caledonian. The tectonic-metamorphic events of the Finnmarkian stage were broadly coeval with the emplacement of basic and alkaline igneous bodies of the Seiland Igneous Province which were introduced from 552 ± 17 Ma (syn-D1) until 501 ± 27 Ma (late D2) and which themselves reflect magmatic evolution from tholeiitic to alkaline types.
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