GEOLOGY OF THE WEST POINT QUADRANGLE, NEW YORK 1 3 



general from the north, and, in part, across very long distances, 

 carrying with it many kinds of foreign material which mixed with 

 the materials that belong within the district. Since these local 

 materials are derived chiefly from crystalline hard rocks, the most 

 abundant constituents of the soil especially in its coarser portions 

 are more or less decayed fragments of these rocks. The finer 

 material has come from longer distances in surprisingly large amount 

 and has mingled with coarser matter of local origin. In many places 

 extensive accumulations of fine sands and sandy soils show large 

 amounts of material that could have been derived only from the 

 slates of the Hudson River valley. Occasional boulders of entirely 

 foreign sort must have come from the Catskills, or in more rare 

 cases, even from the Adirondacks. 



As a result of such an origin the soils are of a strikingly mixed 

 type, bouldery, gravelly, or sandy, with preponderance of crystalline 

 material. In many of the valley bottoms and in small areas where 

 irregular distribution of drift made swamps in former times, heavy 

 silts and muck soils have been developed. But there is no simple 

 law of their distribution; each case is dependent on local conditions, 

 only a part of which is dependent upon the rock floor topography. 



In some of the valleys the drift is very deep. The tendency of 

 glaciation in this district was to subdue the relief that must have 

 characterized the Preglacial highlands. Pinnacles of rock were 

 undoubtedly worn down and carried away, and the deeper irregulari- 

 ties or depressions were subsequently filled or partially filled with 

 drift. It thus happens that in some places the soil cover is very 

 thick. In the southeast corner of the quadrangle, for example, the 

 drift is so heavy that few outcrops of rock ledge can be seen, and a 

 very critical structural relation belonging to that area is hopelessly 

 obscured by the heavy drift. 



The district does not show any particularly valuable or excep- 

 tional type of soil and in the nature of the case, no particular quality 

 could be expected to cover a large area. This is a district, therefore, 

 where it is not safe to assume that any piece of land carries good 

 soil simply because it is surrounded by or adjacent to land which is 

 known to be good. There is no residuary soil of economic conse- 

 quence. A few remnants of residuary soil have been observed and 

 one^ of these cases in particular has been the cause of considerable 

 attention in connection with the construction of the Catskill 

 aqueduct. 



^ This is the north end of the Garrison tunnel ; for a description of it, see 

 chapter on Engineering geology. 



