GLACIAL GEOLOGY OF THE COHOES QUADRANGLE 3I 



At the base of the clay bhiffs and in places extending well out 

 toward the middle line of the valley there are low heaps or sloping 

 banks of mixed clays and sands that have been washed down or 

 have slidden in loosened masses from the slope. At a number of 

 places there are evidences that landslides of considerable propor- 

 tions have occurred. Thus on the left bank of the river above 

 Stillwater, near the Washington-Rensselaer county boundary lines, 

 the broken slope and partially detached masses of the clayey 

 materials are quite evidently the result of landslides. Also 2 miles 

 north of Water ford there is a conspicuous sloping bank, marked by 

 the curve of the Champlain canal, which is believed to represent a 

 landslide. The conditions and factors determining the occurrence 

 of landslides of the Hudson valley clays have been carefully studied 

 by Newland.^ 



It is quite probable that a considerable proportion of the fine- 

 grained materials of the soils of the valley floor have been derived 

 as silts washed from the numerous ravines that open into the val- 

 ley. There are, however, no well-formed alluvial fans fron'ing 

 the mouths of the ravines. In explanation of this it is to be remem- 

 bered that the development of the ravines began as soon as the 

 terraces emerged from the Lake Albany waters and that the sedi- 

 ments washed from the ravines were for a long time spread out 

 on the bed of the lake when its shore line corresponded with the 

 present bluffs of the lower terrace. 



There occur here and there on the valley floor deposits of gravels ; 

 that is, rounded pebbles and cobbles, usually mingled with coarse- 

 grained sands. Some of these occurrences admit of ready explana- 

 tion. For instance, on the eroded tract crossed by the road that 

 runs southwesterly from Reynolds the gravels, forming much of 

 the soil of the fields, have evidently been derived from the materials 

 of the Hoosic delta. The currents which reduced this portion of 

 the front of the delta mass left behind the coarser parts which 

 were too heavy to be transported. 



There are frequent occurrences of masses of gravel in which 

 there is a stratified arrangement of the materials. Immediately 

 north of Waterford, in the angle between the canal and the highway, 

 there is a conspicuous gravel bank in which the following features 

 of composition and structure were noted: (i) Layers of coarse 

 gravel mixed with dark sand 3 to 15 feet thick and 10 to 15 feet 



'Newland. Landslides in Unconsolidated Sediments. 12th Rep't of 

 the Director of the State Mus., p. 79- 1916. 



