Namsvatnet med en del av Frøyningsfjell.

Abstract

The rocks of the area can be divided into three sharply separated groups. These are in ascending tectonic order: 1. The Børgefjell Massif in the north-eastern part of the area. 2. A complex of low-grade metamorphic sediments and volcanics. 3. A complex of high-grade metamorphic schists and gneisses in the west part of the area. The Børgefjell Massif is built up of granitic gneisses, porphyroblast schists rich in albite-oligoclase and micaschists, with subordinate bands of quartzite. There is a sharp tectonic boundary with a structural conformity to the overlying rocks. The Børgefjell Massif is thus a basal gneiss massif in the sense of Olaf Holtedahl. Probably its rocks are of pre-Cambrian age. The granitic gneisses and schists are in alternating, rather flat-lying sheets. East of Store Namsvatnet a beautiful anticlinal structure appears.