STRATIGRAPHY, TECTONOSTRATIGRAPHY AND THE ACCRETION OF OUTBOARD TERRANES IN THE CALEDONIDES OF SUNNHORDLAND, WEST NORWAY

The Caledonides between Karmoy and Bergen in western Norway represent one of the best studied sections of the Scandinavian Caledonides, and the area is of particular significance with regard to the geological evolution of the Caledonian outboard terranes. These terranes include ophiolites of Early Ordovician age, immature to mature island-arc and arc-basin lithologies of Early to Middle Ordovician age and Late Ordovician to Early Silurian unconformable transgressive and regressive sequences. The stratigraphy, including several unconformities, as well as the tectonothermal evolution of this composite terrane, demonstrate that the assembly of the terrane was associated with deformation, metamorphism and syntectonic emplacement of arc plutons prior to the Scandian continental collision between Baltica and Laurentia. The evidence for the pre-Scandian deformation of these rocks has previously been used as an argument for the accretion of oceanic rocks to Baltica prior to the Scandian orogeny. We dispute this interpretation and conclude that the early Caledonian deformation of this terrane occurred within the Iapetus Ocean.