1914—15] Fjeldbygningen mellem Sørfjorden og Samnangerfj orden. 255 



south-east, and may thus be said to form a contrast to the two 

 Bergen-arches. 



If we consider the rocks within the part of the "Outer Bergen- 

 Arch", which lies between Sørfjorden and Samnangerfjorden, we 

 shall find that all of them bear obvious marks of the influence of 

 the one-sided pressure. Thus the various rock-zones are strongly 

 stretched into one direction, and the same extension in one direction 

 is also present in the single components of the rocks. We have 

 thus seen how the longitudinal direction of the conglomerate-blocks 

 lies parallel to the direction of the pressure in the area, and shows 

 clear and in part strong traces of pressure. The compression 

 gradually appears stronger toward the north. The new minerals 

 formed by this dynamical metamorphism are characterized by their 

 small molecular volume. The most common and most important of 

 them also hold O H, thus for instance, sericite (H 2 K Al 3 Si 3 12), 

 chlorite (m H 4 Mg 3 Si 2 9. n H 4 Mg 2 Al 2 Si 9 )> tale (H 2 Mg 3 

 Si 4 12), serpentine (H 4 Mg 3 Si 2 9), and zoisite (H Ca 2 Al 3 

 Si 3 O13). 



All this indicates that the metamorphism of the rocks here 

 mentioned, must have tåken place in the upper part of the earth's 

 crust ; where the one-sided pressure and the amount of water must 

 have been comparatively great. and the temperature relatively low. 

 By the metamorphism the sedimentary rocks have been altered 

 into quartz-phyllites, sericite-phyllites, alum-slate-phyllites, quartz- 

 sericite-schists, epimarbles, stretched conglomerates and conglomerate- 

 gneisses. The basic igneous rocks rich in olivine have become serpen- 

 tines, serpentine-schists, soapstones and talc-schists, and the other basic 

 eruptives, diabases and gabbros, have become saussurite-diabase-schists, 

 zosite-hornblende-schists, flaser-saussurite-gabbros and the like. The 

 granites have assumed a more or less developed cataclastic struc- 

 ture, and by the crushing of felspar and quartz a parallel struc- 

 ture has been formed. These rocks are also often characterized 

 by eyes of more resistant mineral grains. Thus we get a kind 

 of eye-gneisses. With the knowledge we have gained in regard 

 to the composition of the "Outer Bergen-Arch", it will now 

 be of interest to endeavour to draw a comparison between this 

 arch and the inner-one. In the work '"Silurian fossils and com- 

 pressed conglomerates in the Bergen-schists" (p. 83). Dr. Reusch 

 wrote in regard to the relation between the inner and outer arch 

 as follows: '"Nor does it seem to me that there is any petrographic 



