58 



HISTORICAL GEOLOGY 



New York, through the Appalachian range, south of Lake Superior, 

 southeastern Missouri, Oklahoma, central Texas, and at various 



Fig. 26 



Map showing the surface distribution (areas of outcrops) of Cambrian, and 

 some very closely associated Lower Ordovician, strata in North America. 

 (Modified by W. J. M. after Willis, U. S. Geological Survey.) 



places in the Rocky Mountain region. Because Cambrian rocks 

 have so often been removed by erosion, or have been so largely 

 covered by later sediments, or highly folded so that outcropping 



