GEOLOGY OF THE BI UE MOUNTAIN QUADRANGLE 53 



ice sheet. The maximum depth of Blue Mountain lake is said to 

 be about 90 feet. If so, it appears that this basin has, very locally 

 at least, been ice eroded to a depth below any possible Preglacial 

 outlet. The comparatively soft Grenville rocks of this basin would 

 have been very susceptible to ice erosiom The basin of the third 

 of the Chain lakes, mostly in soft Grenville limestone, is said to 

 have a depth of 40 or 50 feet and it may thus also have been locally 

 somewhat deepened by ice erosion. 



The present water levels of the existing lakes all appear to be 

 held up by glacial drift dams, usually across the outlets. Notable 

 exceptions to dams across the outlets are Blue Mountain lake with 

 drift dam across the eastern end, and Long lake with drift dam 

 blocking a Preglacial channel on the east side of the present lake 

 either i^ miles south of the outlet of the lake or about 2 miles 

 northeast of Long Lake village. The first named locality is much 

 the more likely as will be pointed out below. South pond, judging 

 by the rock ledges across the outlet, appears to be held up by the 

 heavy morainic deposits just southwest of the pond. 



Xone of the existing lakes appear ever to have been more than 

 10 or 15 feet higher than their present levels. Along the shores 

 of Long Lake there are occasional sand flats or delta deposits 

 representing a former lake level 8 or ib feet higher than the present. 

 Perhaps the best of these sand fiats is one-quarter of a mile long on 

 the south side of the cove i>^ miles southwest of Long Lake village. 

 There is no evidence that Blue Mountain lake was ever more than 

 a few feet higher than now. 



Drainage Changes Due to Glaciation 



As would be expected, because the watershed between the Hudson 

 and St Lawrence basins passes across the quadrangle, there are 

 certain rather delicately balanced drainage conditions. 



Blue Mountain-Eagle lake basins. Before the ice age the basins 

 now occupied by Blue Mountain and Eagle lakes quite certainly 

 drained eastward into the Hudson river by way of Rock river 

 instead of westward as at present through Raquette lake and thence 

 northward into the St Lawrence (see figure i). Evidence in sup- 

 port of this view is twofold, namely, the rock barrier at the eastern 

 end of Utowana lake and the drift dam at the eastern end of Blue 

 Mountain lake. Rock ledges are practically continuous across the 

 narrow channel at the eastern end of Utowana lake, while the 

 channel connecting Eagle and Blue Mountain lakes is entirely in 



