Rocks of the Jotun stem between Tyin and Böverdalen fall into two groups: (a) peripheral gabbros, and granitic rocks of amphibolite facies metamorphism, sometimes retaining igneous textures and (b) a core of ultramafic rocks and pyroxene-gneisses of pyroxene-granulite metamorphism. The core is coextensive with the deep, dense root of the Caledonides on the geophysical model, the peripheral group with a widely-extending shallower sheet. The structure of the two groups is described. In the light of recent work on the surrounding Eocambrian, it is proposed that the peripheral group was in part emplaced magmatically at high level, eroded and unconformably covered by Eocambrian sparagmite, whilst the core rocks were metamorphosed at pressures > 4kb and tectonically elevated from a root in the Faltungsgraben during the Caledonian orogeny.
A geological traverse across the pyroxene-granulites of Jotunheimen in the Norwegian caledonides