44 ^'E^^' YORK STATE MUSEUM 



mostly in a narrow rock channel, for at least 2 miles, this being due 

 to the fact that the position of the channel there has been determined 

 along the crushed zone of weakness. Along this gorgelike channel 

 wide crushed-rock zones are beautifully developed at many places, 

 one fine example being in the Grenville white gneiss about 1^3 miles 

 due north of the village. The continuation of the fault across the 

 valley west of Indian Lake village is not actually demonstrable, the 

 outcrops being scarce with heaAy drift covering the apparently 

 critical localities. Its extension along the Squaw brook valley of 

 the Indian Lake sheet is, however, certain as shown by the topog- 

 raphy and the presence of crushed-rock zones. 



Somewhat higher altitudes immediately on the eastern side of 

 this line of fracture within the adjoining Indian Lake and Xew- 

 comb quadrangles, suggest that the upthrow side is on the east, 

 though the difference is not enough to make this at all certain. The 

 prominent scarp northwest of Indian Lake village is due to differ- 

 ence in rock character rather than faulting, the Grenville limestone 

 on the east side having been much more readily Avorn down than 

 the relatively hard gneisses on the west side. If any movements 

 took place along this line of fracture since the existence of the 

 Cretaceous peneplain, they must have been relatively slight. The 

 principal movements are certainly much older and they may pos- 

 sibly date back to Precambrian time. 



Indian Lake fault. This long prominent fault, with northeast- 

 southwest strike, has but 2 miles of its course across the south- 

 eastern comer of the quadrangle. The granite porphyr\^ near the 

 western end of the Indian Lake dam is full of shear zones and 

 much of the rock is broken up into a multitude of small blocks. 

 Just at the end of the dam there is a distinct slickensided fault 

 scarp 100 feet long and 15 feet high with some fault breccias. This 

 scarp dips 80° west. There is also a distinct crushed zone parallel 

 to this in the eastern of the two quarries just across the river. No 

 other exposures of the zone of fracture were seen within the 

 quadrangle, but it continues with \try prominent topographic in- 

 fluence into both the adjoining Newcomb and Indian Lake sheets. 

 The remarkably straight channels of the Indian and Hudson .rivers 

 on the Newcomb sheet are almost certainly developed along a fault 

 which is but a continuation of the Indian Lake fault. 



On the Indian Lake sheet this fault has a most decided topog- 

 raphic influence, the long, straight, Indian Lake depression having 

 been determined along the zone of weakness with the SnoA\y 



