 This region consists of Cambo-Silarian sedimentary rocks (i.e., rocks from the Cambrian, Ordovician and Silurian formed 545-417 million years before the present) that are highly metamorphosed by the Caledonian orogeny 490-390 million years ago (Ma).The mountain formation created extensive folding with numerous anticlines and synclines across much of Norway.In addition to Cambrosilurian shales, there are numerous volcanic intrusive sills and dikes.