48 NEW YORK STATE MUSEUM 



of today, and the character of this flat bottom as a late Tertiary 

 peneplain is also manifest when one views it from the summit of 

 Waterman hill. It is interesting to note how closely this series of 

 events parallels those that preceded the Potsdam deposition, when 

 a mature Precambrian peneplain was gently elevated and corroded, 

 just prior possibly to glaciation. Once again that sort of a mature 

 peneplain, hewed mostly across the same crystalline rocks and at 

 very nearly the same level in them, is gently uplifted and incised 

 just before glaciation. In our immediate region the coincidence 

 of the two planes is so intimate that one can not be sure it is not 

 actually' the reuncovered sub-Potsdam peneplain that we see from 

 Gouverneur or Canton. The writer would be unwilling to assert 

 too confidently that it is not just that, though theoretically the 

 Mesozoic plain should control as one goes southward. On account 

 of the warping and probable disfiguration of the older plain (figure 

 2) by the later movements already discussed, it seems more likely 

 that this very conspicuous, smooth, upland surface is the product 

 of the much later period of erosion which elsewhere has given 

 us the well-known late Mesozoic (Cretaceous) peneplains.^ 



Over this surface, then, probably wandered the huge dinosaurian 

 reptiles of those days, and above them flew the dragonlike ptero- 

 saurs. But the morasses and river silts into which their skeletons 

 fell have long since disappeared from here by erosion, and nothing 

 remains of their gruesome occupancy. After them came the great 

 mammals of the Cenozoic (Tertiary) ; and they too have passed 

 away, along with the land surface on which they trod. Yet the 

 St Lawrence region as they saw it must have been in many ways 

 a good deal like the present, with many of the same hills and 

 valleys.^ 



The closing chapters are those of the ice invasions and their 

 aftermath of glacial lakes and marine submergence, a brief account 

 of which follows. 



SURFACE GEOLOGY 



The Pleistocene geology of the Canton quadrangle is fully as 

 complex in its mappable elements as is that of the rocks, and since 

 these can not therefore be shown on the present map, they will be 

 merelv summarized here. 



^ The currently assigned ages of these peneplains (preferably spelled 

 " peneplanes ") has been lately (1916) questioned by Eugene Wesley Shaw 

 at the Albany imieeting of The Geological Society of America. Mr Shaw 

 believes them to be of much more recent date. G. S. A. Bui. 28:128. 



