Egersund. Fjeldbygningen inden rektangelkartet Egersunds omraade

Abstract

Forkortet: The principal part of the rocky underground consists of labradorite-rocks, as may be seen on the map. These are not homogeneous all over the area neither with regard to the mineralogical composition, nor regarding the structure. According to their ineralogical composition, the labradorite-rocks of the Egersund-area may be divided into two large groups, without regard to the different basic differentiation-products: labradorites andlabradorite-norites. The former consist exclusively of labradorite feldspar, whereas the latter besides containing plagioclase, also contain some ferro-magnesium-silicates, ilmenite and apatite, and form a petrographic transition between the pure labradorite-rocks and the norites. The two types of labradorite-rock are as a rule united to each other by different connecting links, in some places, however, they appear to be more sharply separated. In a place SE of Egersund it seems as if a dyke from a labradorite-norite-area has penetrated the pure labradorite-rocks. In perfect correspondence to this the author has found at some places, for instance at the railway station of Klungland and at Solbjørniben in Bjerkreim, fragments of a light labradorite-rock in a darker labradorite-norite. In the author's opinion, however, there is no important difference of age between the various types of labradorite-rocks