GEOLOGY OF THE REMSEN QUADRANGLE 



35 



such thickness as 300 feet of limestone can here be present. In 

 other words a well starting at the top of the Trenton at Bardwell 

 Mill would strike the Precambric much short of 300 feet. The 

 thickness of the Trenton here is probably not much over 150 feet. 

 This thickness compared with the greater thickness at Trenton 

 Falls and in the wells farther south and southwest is what would 

 be expected in the case of an overlap. 



THE PRECAMBRIC SURFACE 

 Smoothness of the floor upon which the Paleozoics were deposited 



There is considerable evidence to show that the Precambric floor 

 which received the Paleozoic sediments was a comparatively smooth 

 one (peneplain). Although the exact boundary line between the 

 Paleozoic and Precambric rocks can not be drawn because of the 

 heavy drift covering, nevertheless there are sufficient exposures 

 on either side to indicate that the line is at least a fairly regular 

 one as shown upon the map. Such a boundary line would be 

 caused by deposition of sediment upon a smooth surface and by 

 later elevation when the sediments would tend to wear off rather 

 regularly. 



Or again the smoothness of the Precambric floor is suggested by 

 the absence of isolated Paleozoic areas within the general Precam- 

 bric district and also by the absence of isolated Precambric areas 

 within the general Paleozoic district. If the Precambric floor had 

 been a rough surface, isolated areas (outliers and inliers) would be 

 expected, near the boundary line at least, where on the one hand 

 sediments had been filled into deep Precambric depressions or on 

 the other hand where Precambric knobs or hills would protrude 

 upward into the sediment and by later erosion become exposed to 

 view. Such outliers or inliers have nowhere been found. 



If the depressions occupied by the present streams of the Pre- 

 cambric area were completely filled the resulting surface would be 

 a comparatively smooth one sloping southwestward. This strongly 

 suggests that the old floor was fairly smooth and that the rather 

 rugged topography now existing has been produced almost entirely 

 by stream erosion since the stripping off of the sediments. 



There is reason to believe that the surface was not entirely free 

 from small hills or knobs which rose above the general level. In 

 the adjoining Little Falls district Professor Cushing has described 

 a very clear-cut example of such a knob at Diamond hill 1 . Myers 



1 N. Y. State Mus. Bui. 77- P- 57-58. 



