144 NEW YORK STATE MUSEUM 



until the vicinity of Cold Spring, West Point and Constitution 

 island are reached. From Cold Spring southward to Fort Mont- 

 gomery prominent rock terraces on both sides of the river doubtless 

 mark this Tertiary history. West Point is located in part on this 

 terrace. A considerable area in the vicinity of Garrison and south- 

 ward is on the terrace as well as Highland Falls on the opposite 

 side of the river. It is rather striking that these terraces are so 

 prominent in this portion of the valley whereas they are not apparent 

 at all at the northern gateway or at the southern gateway between 

 Dunderberg and Anthony's Nose. The reason for it, no doubt, is the 

 fact that the rocks in this inteiwening belt are chiefly Grenville 

 gneisses, schists and limestones, and on them erosion has accom- 

 plished much more than on the massive intrusive members repre- 

 sented at the other places. 



The very decidedly different appearance of the valley walls in 

 these different sections at first suggest the possibility that the river 

 did not have its present course at all in Tertiary time at the two 

 extremes of the gorge through the Highlands but did pursue the 

 same course in the intermediate section between West Point and 

 Fort Montgomery. Although it is not probable that such a change 

 took place at this time it may very well be that the drainage immedi- 

 ately following the Cretaceous peneplanation was quite different 

 from the present and that more prominent drainage than is carried 

 at present came down through the Qove creek-Foundry brook 

 depression, helping to develop a topography quite out of keeping 

 with the present importance of the tributary stream draining this 

 broad depression. In this middle section, the river follows the major 

 rock structure perfectly, but elsewhere it does not. It appears, 

 therefore, to be strictly a superimposed stream with only partial 

 adjustment. 



Minor oscillation. Physiographers have argued in favor of minor 

 oscillation of level in addition to these major movements. It is plain 

 that, subsequent to the mid-Tertiary base-levelling stage, a rejuvena- 

 tion was inaugurated by uplift, and that trenches were cut into the 

 somewhat widened valley bottoms by the streams of that time. This 

 subordinate erosion stage has in most places in this quadrangle 

 entirely obliterated all traces of the former base level, but in 

 occasional stretches, as indicated above, terraces are still preserved. 



It is possible, that other epochs of depression should also be 

 noted in a complete history. If that is true, deposits ought to have 

 been formed in the Hudson valley across this district, but no trace 



