REPORT OF THE DIRECTOR I916 33 



Kaaterskill and Durham quadrangles besides parts of the Gilboa, 

 Hobart, Delhi, Margaretville, Neversink, Slide Mountain and 

 Rosendale quadrangles. 



Within this area, all the principal valleys and those of all but a 

 few of the smaller tributaries were examined. Almost all the sur- 

 face was seen from a greater or less distance. 



Types of glacial deposits. On account of the prevailing rugged 

 relief of the region, the glacial deposits, with the exception of the 

 ground moraine or till, are rather strictly limited to the valley 

 bottoms and lower slopes and are absent, or very weakly developed, 

 on the steeper slopes. To trace moraines from one valley across 

 the intervening ridges to another is, therefore, commonly difficult 

 or impossible, hence the correlation of moraines in adjacent valleys 

 can not always be made with certainty by this means. 



The types of glacial drift distinguished on the map include till, 

 thick nonmorainic drift, drumlins, kames, eskers, and glacial lake 

 and outwash deposits. Smooth-topped deposits of thick non- 

 morainic drift proved to be widespread. They differ from 

 moraines in that the characteristic irregular topography and 

 looped form are lacking. In many places they seem to have been 

 formed by the accumulation of debris beneath the ice, and there 

 are all gradations to typical drumlins. Elsewhere they prove to 

 be glacial deposits of various kinds which have been overridden 

 and smoothed by advancing ice. In the upper Schoharie and the 

 Esopus valleys many such smooth-topped deposits were found to 

 be stratified lake clays, sands and gravels covered with a veneer of 

 till. 



The drift filling in the valleys is surprisingly deep. Borings by 

 the New York City board of water supply have established the 

 fact that the rock beds of Schoharie creek and its tributaries in the 

 vicinity of Prattsville lie, roughly, 200 feet below the present 

 beds of the streams. Much of the filling in that vicinity consists 

 of stratified glacial lake clays, but in most places there is a veneer 

 of till on the surface. 



Glacial movements. At the time of its maximum extension, the 

 ice of the continental glacier appears to have completely buried 

 the Catskills, with the possible exception of a few of the highest 

 peaks. The highest definite striae were found on the west spur of 

 Slide mountain at an elevation of 3580 feet, but compact, stony 

 soil, indistinguishable from glacial till, was found at 4030 feet on 

 Slide mountain and at 3900 feet on Hunter mountain. No conclu- 



