1914 — 15] Fjeldbygningeii mellera Sørfjorden og Samuangerf jorden. 215 



quite exceptionally. Bosses and stratified portions of amphibolitic 

 rock are quite common, the structure of the gneiss winding itself 

 round their margins. Granitic veins and bosses occur rarely, but 

 those that do occur never have a coarse-grained pegmatitic structure. 

 Some few small quartz-veins which have been folded and stretched, 

 occur occasionally. In the southern two thirds of Sotra the gneiss 

 has an appearance such as we generally suppose it to be in the 

 deep-lying Archæan, and it is frequently filled with small stratifled 

 granitic inclusions with indistinct borders. Granite in more marked 

 veins, and in irregularly shaped masses, is also very common — 

 these granite injections sometimes swelling to a considerable size, 

 and having a very coarse-grained pegmatic structure. Large 

 masses of medium-grained granite occur, and also larger masses of 

 dioritic and amphibolitic rock. The basic rock is cut by granitic 

 veins, and together with its net of veins the former shows pres- 

 sing and stretching phenomena in accordance with the adjoining 

 gneiss." 



The Silurian Series. 



The two Silurian arenes are marked on the map with fine lines. 

 The outer one, extending from Os via Samnanger and Osterø to 

 the Fensfjord, consists of rocks which are much less metamorphosed 

 than those forming the inner arch, this latter, as may be seen by 

 the map, extending round the peninsula of Lyderhorn, and exten- 

 ding from Bergen on to the northern side of Askø. Following their 

 course northwards, we see both arches diminish in breadth. This 

 indicates a squeezing; and in conformity with this we can trace 

 the increase of the metamorphism of the rock-zones towards the 

 north, a feature especially noticeable in the outer arch. In the south- 

 ernmost part of this outer arch, i. e.. in the traet about Os, the 

 rocks have been comparatively little altered, and remains of fossils 

 have been found in phyllites (altered argillaceous shales), as well 

 as in marble imetamorphosed limestone). These fossils belong to 

 the middle Silurian. In the continuation of the arch by Samnanger 

 the alteration has become more intense, and fossils have been found 

 only quite exceptionally. Still farther north there is no hope of 

 tinding even the slightest indications of fossils, the recrystallisation 

 having progressed too far. The phyllite-rocks in the very north of 

 this zone resemble the phyllitic rocks of the inner arch. Of the 

 rocks found in the outer arch we may mention phyllite, marble, 



