part 4] THE SCANDINAVIAN ' MOUNTAIN PROBLEM.' 397 



the Porsanger Fjord, and also two sections illustrating how, in my 

 opinion, the present structure may be thought to have developed. 

 The original sequence is, according to what has been stated above : — 

 Pre-Cambrian, followed by the Lower Cambrian shale-sandstone 

 series (1), the Porsanger Series (2), with Porsanger Dolomite on 

 the top, then the Raipas Series, etc. (3). The last-named has 

 in pre-Caledonian time been strongly denuded locally, and the 

 Raipas Dolomite is thus only locally preserved. In (3) is included 

 the relatively thin Bossekop Series (sandstones with shales, and at 

 one horizon a tillite). 



The main tectonic feature is a major thrust-plane, T, and other 

 minor thrust-planes, T'. In the drawing there is — for the sake of 

 simplification — indicated only one minor thrust-plane. In fact, 

 because of the enormous general pressure, it is very difficult to 

 identify the thrust-planes in the metamorphic complex itself, but 

 from the arrangement of the rocks we may conclude that they 

 must be present. At the south-eastern border of the metamorphic 

 mass, where the pressure has been somewhat less than in the 

 more central zone of deformation, the existence of thrust-planes of 

 secondary order can, however, be distinctly seen. By the letters 

 AA, BB, CC is indicated in the figure the probable movement of 

 the dolomite masses found in the thrust-complex, according to nvy 

 view. The igneous horizon, the ' intrusive masses ' of the figure, 

 does not show a sharp bordering line against the surrounding 

 rocks, which are of the same general character above and 

 below : in fact, there is a bordering zone with gneissose rocks, 

 the original character of which, whether derived from the granites 

 of the intrusion or from the felspar-bearing sandstones, is 

 generally difficult to decide. This apparent gradual transition 

 from igneous to sedimentary rock in the metamorphic complex, 

 without any distinct thrust-plane here, is natural, if we assume an 

 intrusion causing a metamorphism of the surrounding 

 rock, but very difficult to understand if we should assume the 

 igneous mass to be an overthrust Archaean one. 



It is evident, from a study of the Alten section with its strongly 

 undulating thrust-plane, that in detail the relation of age between 

 the underlying, relatively unaltered, rocks and the metamorphic 

 sedimentary rocks above, must be very different at various places. 

 It depends upon the inclination of the thrust-plane. At the 

 eastern border of the Scandinavian mountain -belt, from the Alten 

 district and far south into Northern Sweden, the majority of the 

 thrust-rocks must be considered as of a somewhat later age than 

 the unmetamorphic below, as the latter here consist only of the 

 Lower Cambrian division (the Hi/olitlius Zone). 



Where, as for example, farther east in Finmarken, and in 

 Jemtland in Central Sweden, the major-thrust-plane occurs much 

 higher up in the Cambro-Silurian Series, thus corresponding to the 

 conditions seen more to the left in fig. 4. we may expect true 

 overthrusts, with older rocks above younger. 



