4 2 NEW YORK STATE MUSEUM 



THE CLOSING STAGES OF THE GLACIAL PERIOD 



Subsequent to the epoch of flooded waters there is a well-defined 

 stage of glacial history marked by the subsidence of the waters of 

 Lake Albany. This stage is recorded by the present features of 

 the valley of Kayaderosseras oreek from West Milton to Saratoga 

 lake. At West Milton the slopes of the valley, which rise to a height 

 of about 40 feet, consist of eroded till at the lower levels and the 

 delta sands of the Milton plain at the higher levels. Farther east, 

 beginning about 1 mile below West Milton, the till alone shows on 

 the slope at the right bank of the stream, while on the left, beyond 

 the strip of eroded till and at a higher level, the sands continue. 

 These relations of the deposits on the valley slopes continue to the 

 head of the gorge which begins about 2 miles from Ballston Spa. 

 In this portion of its course the creek is bordered by bedrock, or 

 by eroded till, back of which, on both sides of the valley, lie the 

 delta sands. For the most part the bedrock rises as cliffs gradually 

 increasing in height downstream and forming a gorge with walls 

 60 feet high at Ballston Spa. There is a fall of 160 feet in the 

 creek in the distance of 3 miles, affording power for many industries. 



It is evident that when Lake Albany began to subside and the 

 delta plain emerged as land surface, Kayaderosseras creek (probably 

 while still receiving waters from the Hudson channel) cut into the 

 delta deposits at West Milton, eroding a broad, shallow channel in 

 the sands. Farther on, the stream, choosing the course of least 

 obstruction, followed for about 3 miles the line of boundary between 

 the sands of the delta and the clayey materials of the till. It then 

 again cut into the sands, dividing the southward-extending lobe of 

 the delta from the fan-shaped mass to the north. At Ballston Spa 

 the stream flowed over the marginal slope of the delta, there dis- 

 charging into Lake Albany and so continuing during the time of the 

 subsidence of the lake waters from the 400 foot level to the 320 

 foot level. As the subsidence progressed the stream cut deeper into 

 the deposits, gradually removing the sands and sinking its bed into 

 the underlying till and, in its lower course, into bedrock. At the 

 place of discharge, at Ballston Spa, a waterfall formed, due to the 

 stream passing over a bluff of rock which marks the boundary of the 

 depressed area, otitinuous with that in which Saratoga lake lies, of 

 the southeastern portion of the quadrangle. Through erosion of 

 the soft shale rocks this waterfall gradually receded up stream, 

 thus contributing to form the existing gorge. 



