THE GREAT SCANDINAVIAN OVERTHRUST 405 



a somewhat thick quartzite schist, wherein occur the copper ores 

 of Areskutan ; and then follow gneiss-like rocks (which some- 

 times include hornblende and sometimes garnets as accessory- 

 constituents), and they, with alternations of hornblende and mica 

 schists, extend up to the summit of the mountain." 



The same sequence is exposed on the eastern side of the 

 mountain, and Tornebohm therefore naturally concluded that 

 " the schists of the Seve Group, in spite of their crystalline 

 structure and their primaeval aspect, are younger than the 

 surrounding Silurian deposits, and that between them occurs 

 a definite geological boundary which is sometimes marked by 

 beds of conglomerate." 1 



This conclusion is represented in a section across Areskutan 

 which is reproduced as fig. 3. Ten years later Tornebohm recog- 

 nised that the superposition could not be trusted, as the relations 



o 



PTu Hfjall ares &u fan 



s?-f A. A. <f 



sf- sc 



h — halleflinta. sell = schist. (Seve Group.) 



9 = quartzite. (Cambrian.) sl= slate with limestone. (Silurian.) 



Fig. 3. — Section through Areskutan after Tornebohm, 1872, representing the Are 



schists as post-Silurian. 



of the Dala Sandstone (now recognised as Algonkian) had been 

 in places inverted by overthrusting; but he still accepted the 

 view that the Seve Group, with the Vemdal quartzite which 

 he regarded as its base, is later than the underlying Lower 

 Palaeozoic rocks, and supported this conclusion by fresh evidence 

 from the district of Herjedalen. 2 



The demonstration by Prof. Lapworth and by Dr. Horn, 

 Dr. Peach and their colleagues of the Scottish Geological Survey, 

 that the superposition of schists over normal sediments in the 

 north-west Highlands of Scotland was due to overthrusting, 

 encouraged Tornebohm to believe that the same process was 

 the cause of the perplexities of mountain structure in 



1 Tornebohm, Afhandl. Sver. Geo/. Unders. No. 9, 1873, P- 4 2 - 



2 A. E. Tornebohm, " Ora Vemdalsqvartsiten och ofriga qvartzitiska bildningar 

 i Sveriges sydliga fjalltrakter," Geo/. For. Fork. vol. vi. (1883), pp. 274-94. 

 pi. xii. and xiii. 



