Geology and structure of Gjerby, Nordland.

Abstract

The island of Gjerøy is made up of acid gneisses with subordinate mixed gneisses which are tightly interfolded with banded gneisses and associated metasediments. The early tight folds are refolded to produce a large-scale interference pattern. Basic sheets which cut the migmatitic banding in the acid gneisses area themselves metamorphosed at amphibolite facies and folded by the earlier set of tight folds. The relationship of the banded gneisses and metasediments to the basic dykes is unclear and the problem of the stratigraphic ages of these rocks unresolved.