THE GREAT SCANDINAVIAN 

 OVERTHRUST 



By J. W. GREGORY, F.R.S. 



Professor of Geology, University of Glasgow 



Scandinavia and Scotland are geologically nearly akin, and 

 some of the difficult problems of Scottish geology may be 

 solved by the Scandinavian evidence, which is often bolder 

 and simpler. 



The two lands were originally both part of the old Con- 

 tinent of Arctis ; and they both have a similar foundation of 

 crystalline schists and gneisses, which in Scandinavia are 

 accepted as Archean. In both countries the older rocks are 

 covered by wide sheets of pre-Cambrian sandstones — the 

 Torridonian of Scotland and the Algonkian series of Scandi- 

 navia. Both countries have fossiliferous Cambrian rocks along 

 their north-western edge, with a wider development of Lower 

 Palaeozoic, and even younger sediments to the south-east of 

 the crystalline mass. That the schists of Scotland were once 

 connected with those of Scandinavia is suggested by their 

 frequent coincidence in strike, indicating that the structural 

 grain of the countries was continuous across the North Sea. 

 The geological connection has, however, often been geographic- 

 ally broken, and the direct land bridge apparently existed last 

 in Pliocene times. 



The student of crystalline schists in Scandinavia has the 

 advantage over the Scotch geologist of the presence, in many 

 localities, of fossiliferous Lower Palaeozoic rocks in close asso- 

 ciation with the schists. In the Scottish Highlands, on the 

 other hand, the fossiliferous rocks are restricted to a band 

 along the north-western edge, except for a couple of localities 

 containing doubtful worm tubes. The structure of Scotland, 

 in its turn, helps to elucidate that of Scandinavia ; for it 

 was research on Scottish geology that explained the occur- 

 rence of fossiliferous sedimentary rocks beneath series of 

 crystalline schists and gneisses. Murchison attributed this 



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