GEOLOGY AND PALEONTOLOGY OP THE SCHOHARIE VALLEY 341 



in the diagrams [fig. 215, 216]. This, according to Davis, appears 

 to have been the origin of the cuestas of central Englana, 



Continuous seaward retreat of the edge of a simple cuesta 

 eventually brings the inner lowland to the point Avliere the top 

 of the soft stratum passes below the level at which erosion takes 

 place. Then the cliJf will slowly be degraded by atmospheric 



Fig. 215 Diagram showing formation of escarpment by erosion of soft stratum under a, 

 and formation of coastal plain strata b 



erosion till it too has been reduced to the level of erosion, when 

 peneplenation will be accomplished [fig. 217, 218]. The same fate 

 awaits the terraced cuesta unless a new lease of life should be 

 given by a renewed elevation. Otherwise the lowest terrace is 

 first doomed to extinction, the others following in succession from 

 below upward till the whole region is peneplaned [fig. 219-221]. 



Fig. 216 Two escarpments due to subsequent erosion of soft stratum under hard 



stratum Z>,along dotted line in fig. 215 



This condition of peneplenation can readily be recognized by 

 the beveled appearance of the strata at the successive outcrops, 

 the thickness decreasing toward the old land from the moment 

 they pass out from under the protection of the overlying stratum. 

 That this thinning is not the thinning natural to strata as we 

 approach the old shore, is shown by the fact that the lithic char- 

 acter of the bed remains unchanged, which would certainly not 

 be the case if we had reached the former shore, and furthermore 

 by the fact that the lowest bed of each stratum is the one found 

 at the thin end of the Avedge [fig. 222], whereas if the thinning 



