70 NEW YORK STATE MUSEUM 



what slickensided, and considerably weathered. The strike of this 

 crushed-rock zone is about north-south, but no other crushed rocks 

 are exposed along this fault zone as mapped. 



The Grenville gneiss in the small gorge of Styles brook is 

 excessively jointed, forming a zone of weakness with strike east- 

 west or parallel to the stream course (see map). Tracing this 

 zone eastward was impossible because of lack of outcrops. 



A fault zone of weakness has almost certainly determined the 

 position of the deep, narrow valley between Pitchoff mountain and 

 the southern end of the Sentinel range as indicated on the geologic 

 map, though actual exposures of faulted or excessively jointed rocks 

 are lacking at the critical localities. 



Other faults. Several nearly vertical faulted joints pass across 

 the small quarry at the southern end of Lake Placid. They strike 

 N 30° E and probably represent a fault zone which extends through 

 the long, narrow, eastern portion of Lake Placid, but, if so, it is 

 everywhere under water. The long, narrow, western side of the 

 lake basin also strongly suggests its origin along a fault zone of 

 weakness, but positive evidence is lacking. 



The group of diabase dikes about a mile east-northeast of Upper 

 Jay are slightly faulted in a number of places. 



Possibly a fault zone has determined the position of the promi- 

 nent valley which separates Catamount and Wilmington mountains, 

 but positive evidence is entirely lacking because of heavy drift 

 covering, and it is possible that simple removal of a large mass of 

 relatively weak Grenville rock by erosion has caused this valley. 



The notch between Mt Whiteface and St Armand mountain 

 suggests a development along a north-south fault zone, but out- 

 crops in the notch do not appear to have been faulted. 



