702 STEINAR FOSLIE 
pressure prevailed during crystallization. This theory was sug- 
gested by A. Harker, and especially after it had been formulated 
and developed by N. L. Bowen* it has aroused keen interest among 
petrographers. In the present paper I have attempted to give 
some examples from northern Norway bearing on this sort of 
differentiation. 
SHORT REVIEW OF THE GENERAL GEOLOGY OF CALEDONIAN 
As known, the Caledonian mountain chain—of late Silurian 
to early Devonian age—traverses the whole length of Norway from 
SSW. to NNE., in its northern part occupying nearly the whole 
breadth of the country. The axis of the chain forms a marked 
geosynclinal depression of the old Archaean Scandinavian shield 
and of the pre-Cambrian peneplain. The depression is filled with 
a very thick series of sediments, strongly folded and metamorphosed. 
It is supposed that the whole of Scandinavia has been covered 
by the Cambro-Silurian sediments, remnants of which are found 
at many places above the Archaean rocks. They are unmeta- 
morphosed and unfolded wherever well beyond the Caledonian 
folding region. Toward this old mountain chain, first folding sets 
in, then we meet an increasing degree of metamorphism, which 
attains its maximum at the axis of the chain. In the same direction 
the thickness of this series of sediments increases markedly. In 
the eastern, unfolded zone (especially in Sweden) the total thick- 
ness is generally only some few hundred meters, in the folded 
but unmetamorphosed Kristiania region the thickness surpasses 
1,000 m., and toward the mountain chain it reaches several thousand 
meters. 
Although no determined fossils have yet been found in the 
metamorphosed sediments of northern Norway, there are several 
reasons to believe that the sediments here represent the same 
Cambro-Silurian series. The original sediments in the geosyncline 
were extensive layers of slates, marls, limestones, and dolomites, 
with subordinate sandstones. The metamorphism has been 
tN. L. Bowen, ‘‘The Later Stages of the Evolution of the Igneous Rocks,” 
Jour. Geol., Vol. XXIII (1915), suppl.; ‘‘Crystallization-Differentiation in Igneous 
Magmas,” ibid., Vol. XXVII (1919), pp. 393 fi. 
