390 PROF. OLAF HOLTEDAHL ON THE [vol. lxxvi, 



the ' mountain problem,' according to Bjorlykke, is the existence in 

 large areas of Southern Norway of a series of felspar-hearing sand- 

 stones, the ' younger Sparagmite of Valdres ' : these are doubtless 

 younger than the Ordovician phyllites, which they uneonform- 

 ably overlie. Through rnetamorphism of this Sparagmite have 

 originated rocks like those making up the sedimentary part of 

 the ' Highland Quartz.' 



Of Norwegian geologists only one (namely, H. Reusch) had, 

 before 1910, to some extent advocated the view of the Archaean 

 age of the igneous masses in certain districts of the mountain- 

 zone in question. 



During the ten years that have elapsed since the Stockholm 

 Congress much work has been done concerning the ' mountain 

 problem,' both in Norway and in Sweden. 



For Southern Norway the idea of the later than Pre-Cambrian 

 age of the igneous masses of the mountain-zone has since 1910 

 been especially emphasized by V. M. Goldsclmiidt, who has pub- 

 lished a series of very important papers on highland geology 1 : on 

 the deformation of the Pre-Cambrian surface, the petrology of the 

 igneous rocks, the rnetamorphism of the sediments, etc. 



In the northernmost part of Norway Th. Vogt and I have made 

 investigations without discovering any facts that indicate a Pre- 

 Cambrian age for the deformed rocks that overlie the unaltered 

 Lower Cambrian sediments (the so-called ' Uyolitlius Zone '), 

 which here, as in Northern Sweden, occur as a narrow belt between 

 the Pre-Cambrian area on the south-east and the metamorphosed 

 masses on the north-west. 



In Northern Sweden, in the Euoutevare district, A. Gavelin ~ 

 found, as a result of detailed study, that the metamorphosed 

 sediments, the * Seve Croup,' probably represent ordinary Cambro- 

 Silurian rocks in a highly-metamorphosed state. As to the igneous 

 masses lying above the ' Hyolitlius Zone ' (in this district especially 

 anorthosites and amphibolites) Gavelin came to the conclusion that 

 they were intruded in the Seve rocks during the period of general 

 deformation. 



Also P. Quensel 3 has pointed out for a region of Northern Sweden 

 (the Kebnekaise district) that there are strong reasons for assuming 

 that, at any rate, a great part of the Seve Group rocks consists of 

 metamorphosed Cambro- Silurian sediments, and that large masses 

 of the igneous rocks are younger intrusives. 



There is no doubt that, at present, the views of the majority of 

 Scandinavian (including the Swedish) geologists, on the 'mountain 

 problem ' are vastly different from those expressed in the Swedish 

 guide-books of 1910. While the principle of thrusting, introduced 

 into Scandinavian geology by Tornebohm, is now to a considerable 

 -extent accepted, the geological age of the masses moved is, by the 



1 Published in Videnskapsselskapets Skrifter, Kristiania, 1912-16. 



2 Geol. Foren. Stockh. Forhandl. vol. xxxvii (1915) p. 17. 



3 Ibid. vol. xli (1919) p. 19. 



