4 o8 SCIENCE PROGRESS 



quartzites. The southern side of the Offerdal valley is formed 

 by a block mountain known as Alsen, which is built of the 

 same rocks. 



According to Prof. Hogbom's map, the Pentamerus Lime- 

 stone {i.e. Silurian of the Llandovery Series) can be traced all 

 round the foot of the Alsen outlier ; and looking across Offerdal 

 to the north, the superposition of the schists above the lime- 

 stones is shown in a section, reproduced as fig. 5. 



The maps and sections of both Tornebohm and Hogbom 

 appear convincing that the only satisfactory explanation of 

 the facts is that the schists have been overthrust above the 

 Lower Palaeozoic sediments. 



From Jemtland, the overthrust has been traced south-west 

 into Norway and northward into Lapland. The evidence in 

 the far north has been collected by several observers, including 



•^ Tp -.... ^er^^ji3{^~ -- ^>>~ , , e „ a i>: £ 





s Contorted Silurian (chiefly Upper Silurian). c = Crushed Sparagmite. 



sch = Schists. (Seve Group.) T.P. = Thrust Plane. 



Fig. 5.— The north bank of Offerdal, after Hogbom. 



Tornebohm, Hogbom, Holmquist, Sjogren," and Svenonius. 1 

 Prof. Sjogren 2 has described the sections around Sulitelma, 

 and Dr. Holmquist 3 the wide area of schists thrust over 

 sediments assigned to the Silurian, to the south-east of Sulitelma 

 and south-west of Qvikkjokk. To Dr. Holmquist 4 is also due 

 the most detailed account of the overthrust area to the south of 

 Tornetrask, the most northern of the great Swedish lakes. The 

 evidence at Tornetrask is very clear, and, by the kindness 

 of Herr H. Lundbohm of Kiruna and the Traffic Manager of 



1 A bibliography has been recently given by Hogbom, Norrland, 1907, 

 pp. 108-9. 



2 H. Sjogren, " Om Sulitelma-omradets bergarter och tektonik," Geol. For. 

 Fork. vol. xviii. (1896), p. 346. 



3 P. J. Holmquist, " En geologisk profil ofver Fjellomradena emellan 

 Kvikkjokk och Norska Kusten," Sver. Geol. Unders. Afhandl. Ser. C, No. 185 

 (1900), 100 pp. 2 pi. 



4 P.J. Holmquist, "En geologisk profil ofver den skandinaviska fjallkedjan 

 vid Tornetrask," Geol. For. 'Fork. vol. xxv. (1903), pp. 27-78, pi. i.-iii. And 

 " Bihang till Tornetraskprofilen," ibid. pp. 373-90, pi. xii. 



