GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 43 



more, within the quadrangle, finely developed crushed zones have 

 been observed in the Grenville as well as in the eruptives. 



Long Lake fault. This fault, with a length of 8^ miles and 

 strike north 30° east, is the longest one within the quadrangle. It 

 has a decided topographic influence, the long, straight, narrow 

 valley now occupied by Long lake having been determined by the 

 crushed-rock zone of weakness. The topography suggests its con- 

 tinuation for at least a few miles into the Raquette Lake quadrangle, 

 and it almost certainly continues the length of Long lake and .thence 

 probably along the channel of Calkins brook across a part of the 

 Long Lake sheet. The evidence for the continuation of the fault 

 beyond the limits of the Blue Mountain quadrangle is, however, 

 largely topographic, since but few field observations were made by 

 the writer there. 



Passing diagonally across the ledge at Buttermilk falls (plate 7) 

 there is a very distinct crushed-rock zone of considerably decom- 

 posed rock 2 or 3 feet wide and traceable for 50 yards with strike 

 north 30° east. Just on the east sid^ of the falls there are two 

 smaller broken-rock zones parallel to the first. Other places where 

 broken-rock zones, with strike north 30° east, may be seen are on 

 the west shore of the lake three-fourths of a mile north of Grove 

 (Deerland) ; on the shore of the lake just south of the Adirondack 

 Hotel in Long Lake village ; on the lake shore nearly one-half of a 

 mile northeast of the eastern end of the bridge across the lake (at 

 the brecciated diabase dike) ; and on the eastern shore of the lake 

 directly east of Triplet hill where a long ledge shows a broken-rock 

 zone 20 feet wade. 



There is no satisfactory evidence for a determination of the up- 

 throw side or amount of displacement of this fault. At present 

 one side of the fault is not notably raised alDOve the other, thus 

 suggesting that any displacement along the fracture zone antedated 

 the development of many of the fault scarps and blocks of the 

 eastern and southeastern Adirondacks. The movements may have 

 taken place even as early as Precambrian time as suggested by 

 Gushing for similar phenomena on the Long Lake sheet. 



Cedar river-Squaw brook fault. This fault, with north 30° east 

 strike, extends for over 6 miles across the southeastern corner of 

 the quadrangle, being coincident with the course of Cedar river 

 north of Indian Lake village and continuing southward along Squaw 

 brook of the Indian Lake sheet for fully 6 or 8 miles. Due north 

 of the village, Cedar river follows a remarkably straight course, 



