Geologiske undersøkelser i den sydøstligste del av Helgeland.

Abstract

Helgeland is the southern part of northern Norway. The writerand his assistants have worked in the northern part of the area shownon the map, the southern part of the same map is based upon thegeological maps in manuscript of the late state-geologist SteinarFoslie. Foslie's working area was the Grong District, thenorth-easternmost part of southern Norway, known for its large pyritedeposits. The thrust-line on the map, fig. 1, separates a western andtectonically higher complex of highly metamorphosed rocks, includingmuch of granites and gneisses, from an eastern and tectonicallyunderlying complex of less metamorphosed rocks. The thrust is atectonic feature of very great magnitude. The present paper deals withthe rocks of the eastern complex only. In this complex the lowermostunit is the granitic massif of Store Børgefjell, of Precambrian age,according to G. Kautsky (1948). There seems to be little left of theautochtonous cover of the massif, the greater part of the rocks of theeastern area belonging to a thrust-sheet, the Seve nappe. In the areaabout 64 degrees 48'N, 13 degrees 53'E a series of phyllites andquartz-schists, the Røyrvik series of Foslie, contains a limestone inits lower part, and greenstone (meta-basalt) interbedded at twohorizons.