SIXTH REPORT OF THE DIRECTOR IO/X) 1 3 



large way the ridges trend northeast and southwest, yet this 

 general structural feature is modified by two broad north and 

 south valleys, of which the larger, the famous " Keene valley," 

 contains the chief settlements and the smaller is marked by 

 Elk lake. These latter valleys are believed to be old topographic 

 depressions which have antedated the northeast and southwest 

 faults, the causes of the later ridges. 



The northwestern portion of the quadrangle is occupied by a 

 great gravel flat standing" at approximately the 2000 foot con- 

 tour and much cut up by the streams. Over at least 10 square 

 miles of area, no bed rock exposure is visible and one is forced 

 to conclude that some relatively wide and open valley has been 

 buried by the gravels which were incidental to the waning 

 glacial period. 



The postglacial deposits and the moraines of the ice period it- 

 self have done much to modify the relief and rearrange the 

 drainage. There is good evidence of a lake that must have 

 been impounded by some barrier on the north and that filled 

 the Keene valley during the closing of the glacial period. The 

 gravelly deltas along the sides of the valley admit of no other 

 interpretation and in the case of the terrace on which the Willey 

 House stands just beyond the northeast corner of the quadran- 

 gle, the amount of gravel is so great as to be very impressive. 



There is little doubt that in the preglacial times the area 

 around the Upper Ausable lake drained off to the southwest 

 through the Boreas river and that drift has changed the old 

 order of things. The present divide is in a swampy area and is 

 scarcely 20 feet high. 



There are many precipitous mountain fronts which usually 

 trend northeast and southwest and afford beautiful scenery. In 

 the narrow passes at their feet lakes may be situated, such as 

 the Cascade lakes, the Lower Ausable, and Avalanche. Some 

 of the mountains are also sharp and narrow in their summits, 

 as in the case of the Gothics. Others, like Marcy, are rounded 

 and dome-shaped. 



The hard rock geology is similar to other Adirondack quad- 

 rangles, already described in the bulletins of the State Museum. 

 The oldest rocks are the Grenville sediments which are well 

 shown in the Keene valley. Except for one small patch, ap- 

 parently caught up in the anorthosites just south of the Cas- 

 cade lakes, they do not appear outside this depression. They 

 may, however, lie buried beneath the gravels of North Elba 

 and also of the Elk Lake basin. 



