THE MISSISSIPPIAN PERIOD. 515 



The Lower Carboniferous of Silesia, and of central and southern 

 Russia, differs from that in the western part of the continent, in that 

 it is not all marine, and contains much coal. The coal-field of Moscow 

 covers 13,000 square miles, the system resting conformably on the 

 Old Red Sandstone or its equivalent. The coal-beds are mostly thin 

 and poor. The coal-field of Donetz (southern Russia x ) covers 11,000 

 square miles, and contains 44 workable beds (some of them Upper 

 Carboniferous) which have an aggregate thickness of 114 feet. Work- 

 able coal-beds also occur in the upturned Lower Carboniferous strata 

 on the flanks of the Urals. 



The Lower Carboniferous is wanting in most of central France, and 

 eastward through Bohemia, 2 Moravia, and into the region of the Car- 

 pathians. Here the Carboniferous proper (corresponding to the 

 American Pennsylvanian) rests on older Paleozoic systems. This 

 tract was probably land during the Early Carboniferous period. In 

 southern Germany the Lower Carboniferous appears in the moun- 

 tains only. 



The Lower Carboniferous of southern Europe is not very different 

 from that of the central part of the continent, a fact which shows that 

 the northern and southern parts of the continent, which constituted 

 such distinct and persistent provinces during the earlier periods of 

 the Paleozoic, were now less sharply defined. 



Lower Carboniferous rocks are also found in Spitsbergen, where 

 they rest on the Old Red phase of the Devonian. 



Igneous rock. 3 — The Lower Carboniferous system of Scotland and 

 of central Europe is notable for the large amount of volcanic rock 

 which it contains. Volcanic rocks dating from this period, probably 

 largely from its later part, are found at various points in England, 

 Ireland, and Scotland. In Scotland two great types of eruption are 

 recognized: (1) Plateaus, where the volcanic materials from many 

 vents became continuous over areas hundreds of square miles in extent, 

 the lava sometimes having a depth of 1500 feet; and (2) puys, where 

 the ejections were more local, and centered about the vents which 

 discharged them. 4 As the result of the erosion which has taken place, 



1 It is not always easy to distinguish the Lower Carboniferous from the Coal 

 Measures of Russia, from the literature which is available. 



2 Kayser, Geologische Formationskunde, p. 196. 



8 Geikie, Text-book of Geology, Vol. II; also Ancient Volcanoes of Great Britain. 

 4 Geikie, Text-book of Geology, 4th Ed. 



