part 4] THE SCANDINAVIAN ' MOUNTAIN PKOBLEM.' 393 



very often, not only one, but several stratigraphical divisions of the 

 Cambro- Silurian formations are present. The age of the thrust 

 sedimentary masses depends on the inclination of the thrust-planes 

 and on the depth which their proximal part has reached. As these 

 planes seem to have reached very far clown towards, but generally 

 not below, the Pre-Cambrian surface, the existence or non-existence 

 of thrust-rocks of Sparag mite age may be held to depend upon 

 the primary occurrence or non-occurrence of the Sparagmite 

 Division north-west of the areas where the thrust-masses now 



In order to illustrate this statement, we may briefly consider the 

 tectonic features of two widely- separated Norwegian areas where 

 I have made personal investigations. 



The first is Finmarken, the northernmost district of Norway. 

 There, in a north-western belt, occur the metamorphic rocks of the 

 mountain-zone, as will be seen from the map (fig. 2, p. 392). In 

 this belt large igneous masses (granites, gabbros, etc.) occur, 

 especially in the north-west, that is, in the central belt of deforma- 

 tion, where the Pre-Cambrian surface must be situated at a very 

 considerable depth. Th. Vogt found these rocks there to be 

 younger intrusive masses, intruded into the mica-schists, quartzites, 

 etc. Also in the south-eastern part of the metamorphic zone 

 corresponding igneous rocks are found, mostly much crushed, often 

 gneissose, granites, also gabbros, here making up a distinct horizon 

 in the huge cover of stratified rocks, which in the far south-east 

 is seen to overlie the unaltered Lower Cambrian shale-sandstone 

 series, the ' Hyolithus Zone.' The base of this metamorphic cover 

 ^generally represents a typical thrust-plane, which is seen to have 

 a rather undulating character. This undulation of the bordering 

 plane between metamorphic and non-metamorphic rocks is illus- 

 trated in the sections (tig. 4, p. 396), and is also evident from a 

 study of the map (fig. 2). While in the western part of Finmarken 

 only 450 to 500 feet of unaltered sediment come in between the 

 sub- Cambrian peneplane and the metamorphic cover, we find farther 

 north-east, as in the Porsanger Fjord, below this cover about 

 1500 feet of somewhat folded sandstones, with at the top a thick 

 dolomite-layer. This is what I have called the Porsanger Series 

 (Porsanger Sandstone & Porsanger Dolomite). South and south- 

 east of the above-mentioned fjord this Porsanger Sandstone is seen 

 to overlie, doubtless normally, the Lower Cambrian. At the Alten 

 Fjord appears, in a 'window' in the metamorphic cover, the Raipas 

 Series ( sandstone, brownish-weathering dolomite, shale, and green- 

 stone), which nrust be considered of still later age than the Porsanger 

 Series, all these sedimentary divisions being in my opinion of early 

 Ordovician age and belonging to a huge American -Arctic basin of 

 deposition (as I have stated elsewhere). 1 



1 See 'Biclrag til Finmarkens Geologi' Norges Geol. Undersok. No. 84, 1918 ; 

 ' On the Palaeozoic Formations of Finmarken in Northern Norway ' Amer. 

 Jrmrn. Sci. ser. 4, vol. xlvii (1919) p. 86 ; and ' On the Palaeozoic Series of 

 Bear Island, &c.' Norsk Geol. Tidsskrift, vol. v (1919) p. 141. 



