10 NEW YORK STATE MUSEUM 



long, narrow mass of drift, which now extends in a direction 

 approximately parallel with the valley itself. The ridge is broad 

 enough for a highway, yet on the northern side flows a small brook 

 30 or 40 feet below the level of Chapel pond. There may have 

 once been a morainal mass all across the valley into which on the 

 north side the present brook has cut, by removing the finer sand 

 and gravel and by caving down the coarser boulders. Yet as an 

 observer walks or drives along the highway he or she has the 

 striking experience of viewing a pond confined by a natural dam 

 along whose foot flows a brook entirely distinct from the outlet of 

 the pond itself. 



Elk lake, sometimes locally called Mud pond, lies in a broad, 

 drift-filled valley and has swampy extensions. To a less degree 

 the same is true of the Boreas ponds. Both have been enlarged 

 by artificial dams, constructed years ago, so that with the release 

 of the ponded waters logs could be floated down to the sawmills. 

 The broad and open character of these two valleys, heading up as 

 they do so cjuickly to divides a few miles to the north, is a peculiar 

 feature. One would suspect the presence of the soft limestones 

 of the Grenville series, yet in the visible ledges nothing but anortho- 

 site has been discovered. Neither valley can well be the remnant 

 of a large and now obliterated north and south drainage. It is by 

 no means improbable that under the mantle of drift the old weath- 

 ered limestones of the Grenville are hidden. 



Glacial terraces. The mountainous sides of the Keene valley, in 

 common with the other valleys of the region, have a pronounced 

 series of terraces, built of deltas, deposited in successive glacial lakes. 

 The lakes were caused by barriers, presumably of ice, to the north 

 and standing for extended periods at definite levels. Their heights 

 have been determined by Harold L. Ailing.^ 



GENERAL STATEMENT OF GEOLOGICAL FORMATIONS 



The Grenville Series and Its Contact Zones 



The geological formations represented in the Mount Marcy quad- 

 rangle embrace only those of Precambrian time (with the possible 

 exception of some basaltic dikes) and of the Glacial epoch. The 

 geological column is as follows : 



^^pe pages 70 and following. 



