■ THE GREAT SCANDINAVIAN OVERTHRUST 403 



representatives of the Silurian and Ordovician systems ; while 

 beneath the fossiliferous rocks there are beds of alum shale and 

 sandstone which, from their stratigraphical position, are referred 

 to the Cambrian. These eastern rocks are but little altered, and 

 they occur in simple regular sequence, with abundant limestones 

 and fossils. 



The Lower Palceozoic rocks of the western facies are litho- 

 logically strikingly unlike those assigned to the same age in 

 districts farther to the east. The great bulk of the western 

 rocks are schists ; there are but few limestones, and fossils are 

 found only in isolated deposits, which range in age from the 

 Lower Cambrian to the Silurian. The striking lithological 

 differences between the eastern and western rocks is explained 

 as being partly due to more intense metamorphism in the western 

 area ; but this explanation is not alone adequate, as the rocks 

 when first deposited must have been essentially different in 

 composition in the two areas. It is therefore further lexplained 

 that the " Silurian " rocks of the western area are due in part to 

 extensive eruptions of basic rocks, while sediments were quietly 

 accumulating in the seas to the east. 



The Lower Palaeozoic rocks of the western facies are them- 

 selves subdivided into the eastern and western sub-facies ; their 

 relations are somewhat uncertain, and the settlement of this 

 question will be watched with much interest by Scotch geologists, 

 from its analogy to some doubtful points in the correlation of the 

 schists of the Southern Highlands of Scotland. Both the eastern 

 and western sub-facies consist of series of phyllites, clay slates, 

 schists, and gneisses, of which the most highly crystalline rocks 

 belong to the lower division of the eastern sub-facies. 



The rocks vary in metamorphism along their strike ; though 

 why the most highly metamorphosed areas are distributed as 

 shown in Tornebohm's map is not obvious. Thus the Sul 

 Schists extend from north-north-east to south-south-west in 

 a narrow band 2 miles wide and 80 miles long ; and it is marked 

 as strongly metamorphosed for a length of about 22 miles ; 

 whereas the adjacent parallel band of the Meraker and Selbu 

 Schists is strongly metamorphosed for 45 miles farther to the 

 south-south-west. In both sub-facies there are some fossiliferous 

 beds: namely, the Hoilandets group of Trinucleus Sandstone 

 age (Ordovician) in the western series, about 25 miles south- 

 south-west from Trondhjem ; and the Sul slates, containing 



