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Geophys. J. Int. (1992) 109,565-580 Palaeomagnetic dating of fault rocks: evidence for Permian and

Summary: Geophys. J. Int. (1992) 109,565-580
Palaeomagnetic dating of fault rocks: evidence for Permian and
Mesozoic movements and brittle deformation along the extensional
Dalsfjord Fault, western Norway
T. H. Torsvik,'.2 B. A. Sturt,' E. S w e n s ~ o n , ~T. B. Andersen3 and J. F. Dewey2
' Geologicul Survey of Norwuy, PB 3006 Lade, N-7(N)2Trondheim, Norwuy
'Department of Earth Sciences, University of Oxford, Oxford 0x1 3PR, UK
'Department of Geology, Vnlverslty of Oslo, PO Box 1047, Blindern, 0316 Oslo, Norway
Accepted 1991 December S.Received 1991 December 5 ; in original form 1991 September 26
Palaeomagnetic 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 on an earlier Silurian (Scandian) thrust. Fault rocks produced
during subsequent movements indicate that the Dalsfjord Fault underwent periods
of brittle low-angle extensional reactivation during the Permian (250-260 Ma) and
Upper Jurassic/Lower Cretaceous (c. 150Ma), 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. The particular importance of the results is that they show that low-angle


Source: Andersen, Torgeir Bjørge - Centre for Physics of Geological Processes & Department of Geosciences, Universitetet i Oslo


Collections: Geosciences