196 



HISTORICAL GEOLOGY 



widespread submergence toward the end of the period, charac- 

 terized both the succeeding Devonian and Mississippian. The 



Fig. 118 

 Highly generalized paleogeographic map of North 

 America during the Paleozoic era. White areas 

 were the more persistent lands (positive elements); 

 lined and dotted areas were the more persistent waters; 

 dotted areas were the principal geosynclines. (Some- 

 what modified by W. J. M. after Charles Schuchert.) 



Pennsylvanian was characterized by marine conditions in the west 

 and low-lying, swampy lands in the east. During Permian time 

 nearly all of eastern North America was dry land, and alternating 



