82 THE PHYSIOGRAPHY OF CECIL COUNTY 



is explained the meandering courses of the Piedmont rivers of Cecil 

 county. Such streams are said to be superimposed. 



Much discussion has arisen regarding the particular sedimentary 

 beds through which this superposition of the rivers took place. At 

 this time only fragments of the Coastal Plain sediments remain on 

 the surface of the Piedmont Plateau. The rivers which were super- 

 imposed through the cover of unconsolidated deposits have succeeded 

 in removing almost all of the materials through which their sinuous 

 courses were set. This superposition may have been made through 

 the beds of the Potomac group, or through those belonging to the 

 Upper Cretaceous, or possibly through the Lafayette. The most that 

 can be said is that it took place through Coastal Plain deposits, and 

 it is probable that the Lafayette formation had a good deal to do 

 with fixing the courses of the present streams. 



Since the streams have established their courses on the rediscovered 

 surface of the Piedmont Plateau, the region as a whole has undergone 

 an uplift. This elevation has stimulated the erosive work of the 

 streams. As yet, however, only the lower courses of the streams 

 have responded to this rejuvenating influence. These are the por- 

 tions which would naturally profit first by the uplift, and it is along 

 their lower courses that the streams have deepened their channels and 

 flow in gorges, while toward their headwaters, they emerge from their 

 chasms and flow along the surface of the plateau. 



