8 



NEW YORK STATE MUSEUM 



the southern edge of the sheet the valley bottom stands generally 

 above the level of overflow of the present river and its materials 

 are chiefly of glacial origin or, in large areas, of bared rock or 

 residual soils derived from the rock in the recent period. 



L e g e Ti d 



Clav 



- Sands or 

 Clayey sands 



Till 



Rock 



Fig. 2 Section across the Hudson valley showing present surface features 

 and relations of Pleistocene deposits to the underlying rock surface. The 

 surface line is drawn to scale along an approximately east-west line taken 

 about 3 miles south of Mechanicville. 



Rising from the flat valley bottom on either side are steep slopes 

 or bluffs, the materials of which are the stratified Pleistocene clays. 

 From the summit of these bluffs, extending outward from the valley, 

 are expanses of clay or sandy clay lands forming terraces. These 

 terraces occur on both sides of the river at approximately cor- 

 responding levels, showing that they are remnants of a continuous 

 plain that has been divided by the erosive work of the Hudson 

 waters. 



At the outward margin of these terraces the surface again rises, 

 in some places rather abruptly and in other places gradually, form- 

 ing a slope the rise of which is, as a general average, about 6o feet. 

 Outward from the summit of this slope the surface again becomes 

 flat or moderately sloping toward the valley and extends north and 

 south somewhat as a b.ench or terrace normal to the river valley. 

 This area, which will' be referred to in this report as the upper 

 terrace, consists of soils in which there is a larger proportion of 

 sand than in the clay soils of the lower terrace. Beyond the out- 

 ward limit of the upper terrace rise the uplands areas, the surface 

 materials of which consist chiefly of till or materials derived from 

 or left by the melting of the ice sheet. 



Within the limits of the quadrangle the Hudson receives its 

 largest tributary, the Mohawk river, from the west ; and one of its 

 largest tributaries from the east, the Hoosic river. 



