The Møre-Trøndelag Fault Zone (MTFZ) is a set of ENE-WSW oriented upright folds and faults, exposed in the coastal area of central Norway, and traceable across the Northwest European Platform. This fault zone has experienced multiple reactivations from Palaeozoic to Tertiary times, but only its Palaeozoic history is dealt with here. Field observations in the area adjacent to the MTFZ give evidence for top-to-northeast shearing in both parautochthonous basement and allochthonous Caledonian nappes, which is tentatively related to nappe emplacement during Caledonian orogenesis. A series of ORS Devonian basins resulted from left-lateral shearing along east-northeast trending segments of the MTFZ and from extensional detachment along northwest trending releasing bends. Caledonian deformation is overprinted by this Devonian top-to-southwest shearing within a shear zone several kilometres thick which is interpreted as an extensional linked system allowing late orogenic extensional collapse of the Scandinavian Caledonides. Left-lateral transcurrent movement continued on the MTFZ during the Late Devonian and Early Carboniferous.
Michel Seranne, Laboratoire de Geologie des Bassins, Universite Montpellier Il, CNRS-URA 1371, 34095 Montpellier, France.