GEOLOGY OF THE NORTH CREEK QUADRANGLE 69 



wholly derived from without the quadrangle, and especially abund- 

 ant in its northern portion, is the coarse grained anorthosite whose 

 nearest parent ledges are in the northern portion of the Schroon 

 lake sheet. Such boulders several feet across are frequently en- 

 countered. The only Paleozoic rock boulders noted were of Pots- 

 dam sandstone and, as already stated, these are nearly all confined 

 to the Hudson valley between Heath and Moon mountains. 



Glacial till or ground moraine material is quite widespread, 

 especially over the lowlands, but no great thickness was noted at 

 any place. It would seem that more material was scraped off by 

 ice erosion than was deposited as till. As would be expected from 

 the nature of the rocks, the till is always sandy or gravelly and gen- 

 erally filled with boulders. Not a single good example of real 

 boulder clay was observed. 



Karnes are of uncommon occurrence. Three or four good ones, 

 large enough to be shown by the contour lines, lie in the little val- 

 ley a mile west of No. 9 mountain. Some other stratified sand and 

 gravel deposits of rather doubtful kame origin occur in the valley 

 between Chestertown and Tripp pond. 



But one fairly well-defined boulder moraine came to the writer's 

 notice and this is quite clearly traceable as a belt i to 3 miles wide 

 from the vicinty of South Horicon westward around Prospect 

 mountain, thence across the southern part of Loon lake and a 

 mile or so southward, thence over the southern end of the ridge 

 just west of the lake, and nearly to the river. The ice front must 

 have been nearly stationary for some time along this line to allow 

 the accumulation of so many boulders. 



GLACIAL LAKES 



Glacial Lake Warrensburg. This extinct glacial lake, recently 

 described by the writer, is so named because of the location of the 

 village of Warrensburg upon the old lake deposit which is especially 

 well shown as a sand plain area between the village and the Hud- 

 son river. The concordant altitudes of this sand flat, where un- 

 affected by subsequent erosion; the remarkable freedom of the 

 surface from boulders; and the crudely stratified character of the 

 material as shown in cuts all afford conclusive evidence for static 

 water conditions here, the sand ])lain material having been formed 

 as a delta deposit in the lake. This is a good example of a small 

 pitted sand plain, there being two notable depressions (one con- 



