GLACIAL GEOLOGTy OF THE COHOES QUADRANGLE 23 



The Hoosic delta. The Hoosic delta, like the other deltas 

 built by large streams which discharged their sediments into Lake 

 Albany, in its present surface features bears the character of a 

 sand plain. The continuity of the plain is broken, however, by the 

 valley of the present river which has sunk its bed deeply into the 

 sands and, through meandering, swept away a broad path through 

 the delta. The marginal limits of the delta plain are indicated 

 partly by differences in the topographic features of the delta, as 

 contrasted with the terraced deposits above described, and partly 

 by differences in the character of the materials of the two forma- 

 tions. In general, the delta materials as seen at the surface are 

 coarser and less coherent than those of the terraced areas, the 

 proportion of sands and fine gravels being much larger. 



The shape of the delta is that characteristic of this type of con- 

 structional formation. The materials are spread out fanlike from 

 the original head of the delta or place where die river debouched 

 into the lake. This may be taken as at Schaghticoke. The outward 

 margin of the delta mass, fronting the Hudson valley, is somewhat 

 of the form of an arc but this has been considerably modified by 

 river erosion. The Hudson currents, deflected eastward from 

 Bemis Heights, have cut deeply into the northward extension of 

 the delta border. Also, at an earlier time, the Iroquois-Mohawk 

 currents which followed the present course of Anthony kill, sweep- 

 ing across the subsiding waters of Lake Albany, cut deeply into the 

 marginal lobe of the delta at Reynolds forming the upper and 

 lower erosion terraces to be described below. (Further reference 

 to this stage of Pleistocene history will be given below.) 



The surface of the delta plain varies much as to composition of 

 materials and minor topographic features. The soils are for the 

 most part too deficient in clay constituents to be valuable for agri- 

 culture. Considerable areas are left uncultivated and there are 

 tracts of coarse sands where wild vegetation is scanty. The lack 

 of coherence of the soil particles has resulted in extensive gullying 

 of the surface over considerable areas. In the region east of 

 Reynolds the plain is deeply dissected by many ravines producing 

 the irregularities of surface indicated by the contour lines of the 

 sheet. 



The above description applies to the surface materials and 

 features of the delta where the plain has not been reduced by river 



