GLACIAL GEOLOGY OF THE COHOES QUADRANGLE 4I 



REVIEW AND SUMMARY 



The following is a classification of stages of the pleistocene 

 period and present period as recorded on the area of the Cohoes 

 quadrangle : 



NAME OF STAGE PROCESS RECORD 



"§ Recent Stream and wind Alluvium, wind- 



S erosion and depo- blown sands, swamp 



cl, sition muck 



^ Glacio-lacustrine 



^ Substage e. . . . Erosion by fluviatile waters . Erosion terraces and eroded 



'^ bottom of present Hudson 



valley 

 ■^ Substage d.... Later subsidence of Lake 



•S Albany Lower terrace 



^ Substage c. . . . Earlier subsidence of Lake 



Albany Upper terrace 



s Substage b. . . . Lacustrine waters occupy 



S Hudson valley Lake Albany deposits 



t^ Substage a.. . . Ice ' lobe occupies Hudson 



is valley Marginal moraines 



(^ Wisconsin Last general glaciation Till 



Pre-Wisconsin. . . (Interglacial interval) Eroded basin of Saratoga 



lake (?) 



In a previous report^ the writer has presented what seems con- 

 clusive evidence that the Hudson river in its course across the 

 southeastern spur of the Adirondack mountains, from Corinth to 

 west of Glens Falls, occupies a valley cut during an interglacial 

 epoch, immediately preceding the last or Wisconsin period of glacia- 

 tion. On the area of the Cohoes quadrangle, however, no certain 

 evidence of an earlier period of glaciation has been found. But 

 mention may be made of the possibility that the rock depression 

 occupied by Saratoga lake is a part of the valley eroded by the 

 interglacial Hudson in its course southward from the place of 

 emergence from the Adirondack region onto the Hudson plain 

 west of Glens Falls. It has been thought permissible, in the classi- 

 fication above given, to recognize, in a tentative way, this inter- 

 pretation of the rock basin of Saratoga lake with which may be 

 connected that of Round lake, 4 miles farther to the south. W^ood- 

 worth has suggested as follows : "It seems probable that Round 

 and Saratoga lakes are unfilled depressions marking the site of an 

 old valley west of the present Hudson gorge."^ 



^ Glacial Geology of the Saratoga Quadrangle. N. Y. State Mus. Bui. 

 183, p. 30-35- 



' Woodworth. Op. cit. p. 76. 



