A preliminary account on the geology of the Selbu-Tydal area, the Trondheim region, Central Norwegian Caledonides

Sediments and volcanic rocks (ophiolites) all of early Palaeozoic age were metamorphosed, multiply deformed, and intruded by igneous rocks during the Caledonian orogeny. At least six deformation phases including late faults are recognized. There is no simple correlation between deformation phases and tectonic style. The second deformation phase (D2) is accompanied by Barrovian type metamorphism, ranging from biotite to sillimanite grade, and transposes earlier surfaces into a new foliation, which is itself folded on a regional scale. The transposition foliation varies from crenulation cleavage to schistosity. Basic intrusives are rimmed by contact metamorphic aureoles also of syn-D2 age. Acid intrusives are of syn- to post-D2 age. Structural and stratigraphic correlations with nearby areas are attempted. An Ordovician/Silurian age is suggested for the Gula Schist Group.