GEOLOGY OF THE SCHROON LAKE QUADRANGLE 83 



road one-third of a mile west of Oliver pond show many closely 

 spaced joints with nearly north-south strike. These zones of 

 broken rock are apparently minor, and since they have no topo- 

 graphic influence they are not mapped. 



The steep southern face of Moxham mountain strongly sug- 

 gests a fault scarp, but it might have resulted by removal of Gran- 

 ville strata, such rock now forming a considerable belt not far to 

 the south. 



In the bed of Boreas river i mile below Lester dam, the granite 

 is much broken and badly weathered in a fault zone of weakness 

 with nearly north-south strike, but there appears to be no topo- 

 graphic influence. 



In still other places the topography suggests the presence of 

 fault zones, but in no case has the evidence seemed strong enough 

 to warrant mapping. 



PLEISTOCENE GEOLOGY 

 General Statements 



It is well known that, during the great Ice Age of the Quaternary 

 period, all of New York State except portions of the extreme 

 southern side was buried under a sheet of ice. That this great 

 sheet of ice was thick enough to bury even the highest mountains 

 of northern New York is proved by the presence of glacial pebbles 

 and boulders at or close to many of their summits. This is true in 

 the Schroon Lake quadrangle. In some cases striae and glaciated 

 ledges have been observed several thousand feet above sea level, 

 the highest which happened to be noted in the Schroon Lake quad- 

 rangle being at 2200 feet. Adirondack glacial lakes at altitudes of 

 several thousand feet above sea level also bear strong testimony to 

 great depth of ice. The general direction of movement of the ice 

 across the Adirondacks was toward the south and southwest, with 

 comparatively few local exceptions. Such a persistent direction of 

 movement also strongly argues for complete burial of the region 

 under ice. The ice spread southward as a part of the great Labra- 

 dorean ice sheet of eastern Canada. When the ice, early in its 

 southward movement, struck the Adirondack highland district, one 

 portion flowed southward through the Champlain valley and sent 

 a branch lobe westward into the Mohawk valley. At the same 

 time another portion flowed around the western side of the moun- 

 tains and sent a lobe eastward into the Mohawk valley. The two 

 lobes, one from the east and the other from the west, met in the 



