﻿I50 NEW YORK STATE MUSEUM 



area the front was faced by about 400 feet of water in the Red- 

 wood district. Just what that condition implies in its effects on 

 the ice and the drift is uncertain. We do not know whether the ice 

 melted back as a steep, high front under the dissolving influence 

 of the water, or whether it melted as a thinning sheet, partially pro- 

 tected by its scanty drift, until it was lifted by the water and rafted 

 away. 



To epitomize : We conclude that the basins and stronger valleys 

 were excavated by weathering and stream erosion in preglacial or 

 interglacial time, with perhaps some help from early ice erosion ; 

 and that the latest ice sheet had little effect beyond clearing out 

 the debris which it found. 



Glacial deposits 



Introduction. General features. Compared with areas to the 

 southward the area under description has very scanty drift, and 

 has suffered little recent ice erosion. The area did not lie in the 

 zone either of dominant deposition or dominant erosion of the 

 latest ice sheet. Over large portions of the area the rocks are 

 nearly bare, and even in the districts where the drift cover pre- 

 vails the rock appears frequently and unexpectedly. The amount 

 or depth of drift increases southward but the only heavy moraine 

 lies in the southeast corner of the area [pi. 44]. 



In considering the character and distribution of the drift it is 

 necessary to emphasize again the fact that during the ice recession 

 the whole area was submerged in the waters of -Lake Iroquois, and 

 this was followed by the sea-level waters of Gilbert gulf. The 

 marginal drift was all deposited under subaqueous conditions, and 

 wholly subjected to the distributive action of the shallowing waters. 



Over the northern part of the area, where the rock foundation 

 is either Potsdam or Precambric and the land surface irregular, the 

 scanty drift is largely in the depressions, due specially to the work 

 of the shallow waters. Over the southern districts, where the lime- 

 stones form wide plains or plateaus, the drift is usually a veneer 

 giving the broad stretches flat or gently rolling surfaces. Because 

 of the lack of drift the preglacial valleys are still open, and one of 

 the characters of the region is the valleys and basins with steep 

 rock walls and silt-plain bottoms. The valleys of French creek 

 and Chaumont river are open down to Ontario level; and the Perch 

 lake valley is filled to only 70 feet over Ontario. The open char- 

 acter of these southern valleys is to be only partly explained by the 



