832 



PRINCIPLES OF STRATIGRAPHY 



generally spoken of as the subsequents. This inner lowland is 

 bounded on one side by the stripped slope of the old land and on 

 the other by the cut edges of the coastal plain strata. If these latter 

 contain resistant members of limestone or sandstone, they will pre- 

 sent an escarpment or cliff of some steepness. As the inner lowland 

 is widened and deepened the cliff increases in height because lower 

 and lower members of the coastal plain series are discovered by 

 the removal of the overlapping higher members. This will con- 

 tinue until the consequent has reached a condition of grade, and so 

 will arrest further deepening of the channels of its tributaries. 

 Beyond this point the cliff will be gradually lowered, through con- 

 tinued backward pushing, until the plane of erosion and the sloping 



Fig. 206. The same coastal plain as shown in Fig. 205. After dissection 

 and the formation of the cuesta; the broad inner lowland is 

 occupied by the subsequents. 



surface of the coastal plain intersect near the seashore, when the 

 condition of peneplanation is reached. 



The topographic element produced by the dissection of the 

 coastal plain is known as the cuesta. Its main elements are the 

 "inface" or cliff facing the old land, and the gentle outward slope 

 conforming to the slight inclination of the coastal plain strata, and 

 formed by its top member. Between the cuesta and the old land is 

 the stripped belt or inner lowland, occupied by the subsequent 

 stream. This is tributary to the consequent stream, which dissects 

 the cuesta transversely. (Figs. 205, 206.) 



Deposition in dissected coastal plain. A moderately dissected 

 coastal plain in which transverse consequent and longitudinal sub- 

 sequent valleys are formed may be affected by partial subsidence, 

 in which case erosive activity not only comes to a standstill, but 

 deposition will actually take place in the valleys, if subsidence has 

 been sufficient to result in the entrance of the sea into the valleys, 

 and the consequent drowning of the same. Examples of drowned 

 consequent valleys are seen to-day in Chesapeake and Delaware 



