The Caledonian fold belt i Finnmark

Abstract

Forkortet. The Caledonian allochthon in Finnmark embraces 4 major nappes or nappe complexes named, from bottom to top, the Gaissa, Laksefjord, Kalak and Magerøy. Of these the 3 lower nappe complexes acquired their internal deformation struc- tures and largely ductile basal mylonite fabrics (ultracataclasite in the case of the Gaissa) during the late Cambrian-early Ordovician Finnmarkian orogenic phase. The Magerøy nappe, on the other hand, was internally deformed and thrust to its present position during the late Silurian to earliest Devonian Scandian orogenesis. Evidence of Scandian heating and final translation of the subjacent Kalak Neppe Complex is found in radiometric data and in diaphtoretic cataclasites overprintning ductile mylonites.