56 NEW YORK STATE MUSEUM 



Collins brook fault. The Collins brook fault lies nearly parallel to 

 the Holcombville fault and it is named from the small brook which 

 follows the base of the scarp near its north end. It is clearly 

 marked by the topography for a distance of 5 miles between the 

 .Hudson river and Mill creek near Wevertown. The evidence for 

 its existence is threefold, namely: (i) the long, regular scarp of 

 granite whose crest is lined with peaks rising from 300- to 600 

 feet above the base of the scarp; (2) the long, smooth contact of 

 the Grenville against the base of the scarp; and {3) the distinctly 

 eastward downslope of the earth block away from the crest of the 

 scarp. 



Henderson mountain faults. The principal fault of this group 

 strikes northeast-southwest along the western base of the Hender- 

 son mountain mass. Its position is plainly marked by the topog- 

 raphy, and though the scarp is not as steep as usual, it is neverthe- 

 less very prominent and straight and cuts across the foliation of 

 the rocks at a high angle. The sharp swing of the Hudson river 

 northeastward for ilA miles along the line of the fault has 

 been determined by the crushed belt of weakness. North of 

 the river the position of the stream which flows through Bird 

 pond has also been determined by the fault. As judged by the 

 height of the scarp at the south end and also at the base of Hender- 

 son mountain, the displacement is fully 700 feet. Where the fault 

 crosses the belt of mixed gneisses the scarp is much less prominent 

 because of the relative weakness of. the rocks there. No tilting of 

 this fault block is noticeable. This fault certainly continues for some 

 3 miles northward into the Schroon Lake quadrangle along the 

 western bases of Green and Pine hills. 



The second fault of this group strikes almost parallel to the 

 Henderson mountain fault and lies at the eastern foot of the moun- 

 tain whose elevation is 191 5 feet. The very steep side of this 

 mountain rises 700 feet and is another good example of a fault 

 scarp wholly within homogeneous rock. Where the fault passes 

 into the area of weaker mixed gneisses the scarp is much less 

 prominent. 



The third fault of this group is a small one which lies south 

 of Igerna and along the north side of the Hudson river. It is 

 wholly within the area of mixed gneisses but at some places almost 

 vertical scarps rise fully 200 feet. 



Schroon lake faults. The larger of the two faults here de- 

 scribed strikes northeast-southwest and extends along the eastern 



