142 NEW YORK STATE MUSEUM 



Although a very elaborate statement of the physiographic history 

 would not be warranted from a study of this district alone, yet the 

 major steps of that history are represented by very definite features 

 in the West Point quadrangle. 



Cretaceous peneplanation. No upland portions of the area are 

 level and the more elevated portions are far from any strict equality 

 of level. Nevertheless it is true that the profile across the quad- 

 rangle on almost any line northwest-southeast gives heights for the 

 principal ridges that fall into fair accordance. Occasional, points 

 rise above the average level and many fall below, yet it is very plain 

 indeed that the average level rises rather uniformly toward the 

 north and northeast. No doubt this would be still more uniform 

 if it were not for large intrusions of massive granite which stand 

 above the average level. Such cases are Dunderberg on the south and 

 parts of the Storm King-Breakneck ridge on the north (plate 54). 



From such profiles one is impressed with the fact that on the line 

 from Garrison to Peekskill, the average elevation is not far from 

 500 feet. Five miles northeast a similar profile average gives some- 

 thing near to 900 feet and 4 miles farther, the general level runs 

 about 1000 feet (see plate 51 which shows five profiles on a general 

 outline map of the quadrangle). It is very striking indeed that on 

 such a variety of rock quality there should be so uniform limitation 

 of elevation. Perhaps this is due to the Cretaceous peneplanation. 

 It is not probable that these levels already indicated correspond 

 to the Cretaceous peneplain proper, although some of the higher 

 levels may. It is very probable, however, that the Cretaceous pene- 

 plain in this region is indicated not by the highest point, but by 

 the general level of the wider, more elevated portions. The irregu- 

 larities appearing as depressions below that level represent erosion 

 effects since that time. 



Subsequent uplift is shown by erosion of the valleys, but in this 

 region the valleys are all narrow and insignificant compared to those 

 both north and south of the Highlands where the rocks are less 

 resistant. 



Tertiary base level. The Tertiary partial peneplanation seems 

 to be very well marked indeed in the middle Hudson valley north 

 of the Highlands reaching the extreme northwest corner of this 

 sheet along the margin of Breakneck ridge where about 4 square 

 miles of territory lie within the Great valley. No effect of this 

 attempt at base levelling is to be seen in the gateway betweeri 

 Breakneck and Storm King and little evidence of it can be found 



