THE CARBONIFEROUS PERIODS 



471 



In the west 



period the eastern portion of North America was land 

 the seas also seem to have been withdrawn. 



Other Continents. — Missis&Lppian seas spread over a large area 

 in England, Ireland, and Europe, and the sediments which had been 



Fig. 447. — Map showing the probable outline of North America during a portion 

 of the Upper Mississippian. The areas in black show where continental deposits 

 were laid down. (Modified after Schuchert.) 



accumulating in them were locally folded at the close of the period. 

 The term Paleozoic Alps which has been applied to this folded re- 

 gion assumes that the present folded areas are the " roots of former 

 mountain ranges." Whether erosion kept pace with elevation or 

 not cannot be stated. Strata which are believed to be of this age 

 occur in northern and southern Africa, in western and central Asia and 

 China, in Australia and New Zealand, and in Argentina and Chile. 

 Coal occurs in the strata of this age in China, Russia, England, and 

 elsewhere. 



