516 GEOLOGY. 



these volcanic rocks have given rise, in Scotland, to considerable belts 

 of hills and table-lands. Some of these volcanic rocks were probably 

 of submarine origin, and some of subaerial origin. Igneous rocks 

 (chiefly granite) dating from the close of the Early Carboniferous 

 are also abundantly associated with the Lower Carboniferous formations 

 of the Harz, Thuringerwald, Vosges, and other mountains of central 

 Europe. 



Thickness. — The thickness of the European Lower Carboniferous 

 is very great, considering the fact that it is so largely of limestone. In 

 England and Ireland, the limestone attains thicknesses ranging up 

 to 2000 feet, and perhaps even to 2500 feet. In the northern part of 

 England and in Scotland, where the beds are clastic, they have a thick- 

 ness which, at the maximum, is much greater. In Belgium, the lime- 

 stone is also very thick. These great thicknesses, especially of lime- 

 stone, bespeak the great duration of the Lower Carboniferous period. 

 2500 feet of limestone, accumulating at the rate at which limestone is 

 supposed to accumulate, would call for at least some hundreds of 

 thousands, and perhaps millions, of years. The system also has great 

 thickness in Russia. 



Close of the Early Carboniferous period in Europe. — The close of 

 the Early Carboniferous period was marked, in Europe, by somewhat 

 wide-spread crustal disturbances. It was at this time that a great 

 system of mountains, sometimes referred to as the Paleozoic Alps, 1 

 began its development. This system of mountains crossed the central 

 part of Europe, from the islands on the west to the Sudetes mountains, 

 or perhaps beyond, on the east. Their remnants are seen in the Vosges, 

 Black Forest, Harz, Sudetes, etc., mountains of the present time. The 

 development of the Ural mountains appears to have begun at the same 

 time. Geographic changes which were not deformative were also in 

 progress, shifting somewhat the areas of sedimentation. In Europe 

 as in America, therefore, there is a notable break between the Lower 

 and Upper Carboniferous. Unconformity between the two systems 

 is reported along the eastern border of the Schiefergebirge 2 in Saxony, 

 in the eastern Alps, in southern France, and in Spain. 3 These relations, 



1 Kayser, Geologische Formationskunde. 



2 Kayser, op. cit., p. 170. 



3 Credner, Elemente der Geologie, p. 481. 



