of the Northern Catskill Mountains. 163 



Schoharie Creek from Tannersville to Prattsville. A tentative 

 interpretation of the evidence offered by the maps seems legiti- 

 mate, inasmuch as each of the deltas thus far described is very 

 clearly represented on the maps and might have been located 

 with a considerable degree of certainty from a map study alone 

 without field investigation. It would seem, therefore, that if 

 similar deltas occur on the other streams it should be possible 

 to detect them from the maps. 



By a careful study of the maps no sign of any topographic 

 feature resembling a delta could be found at the elevation of 

 the Grand Gorge channel along any of these southern streams, 

 except at Jewett Center (Phoenicia quadrangle) where East 

 Kill empties into Schoharie Creek. Here a bulging spur on 

 either side of the stream looks suspicious. In the valley of 

 Schoharie Creek below Hunter, along West Kill, and along 

 Little West Kill, the contour maps do not give the slightest 

 indication of the presence of deltas ; in spite of the fact that 

 these are good-sized streams flowing in valleys wide enough to 

 have preserved at least some remnants of the deltas had they 

 once been present. Mine Kill and other tributaries to the 

 northwest show no deltas conspicuous enough to be detected on 

 the maps. 



Two possible explanations of the lack of pronounced deltas 

 in the southern arms of the glacial Grand Gorge Lake present 

 themselves : which is correct must be left to future investiga- 

 tors to determine. One is that while deltas were building in 

 the northern arms of the lake, local glaciers, flowing northward 

 from the higher Catskills to the south, filled the southern val- 

 leys and prevented delta building. The second is that the con- 

 spicuous size of the deltas described is due to their having been 

 built by streams issuing from ice tongues heavily laden with 

 sediment and, consequently, able to build up large deltas within 

 a space of time so short that normal non-glacier-fed streams, 

 like those coming from the southeast may have been if local 

 glaciers were unimportant, could do little in the way of delta 

 building. 



If the latter is the true explanation, the delta at Jewett 

 Center, if it proves to be a delta, is significant, since its stream, 

 East Kill, is so situated that it would doubtless be fed to some, 

 extent by an ice tongue pushing south from the gap at East 

 Windham through the low passes south of Hensonville. 



Lake Clays. — Glacial lake clays are conspicuously developed 

 in many places within the area covered by Grand Gorge Lake. 

 They have been noted at Grand Gorge, near Gilboa, between 

 Gil boa and North Blenheim, and on the morainic loop at 

 Devasego Falls, 1 1/2 miles north of Prattsville. At the latter 

 place the clays are thick, very pure, and, in places at least, 

 beautifully stratified. 



