8o NEW YORK STATE MUSEUM 



long, nearly straight line, with hills rising steeply hundreds of feet 

 above it and at right angles to the old rock structures, makes the 

 existence of a line or zone of fracturing there almost certain. This 

 being the case, the outliers of Paleozoic strata in and near Schroon 

 Lake village really lie in a " graben " or fault trough. 



Fuller brook fault. This zone of fracture separates Pine hill 

 and Ledge hill rather sharply and continues northward at least to 

 Horseshoe pond. The topographic evidence is quite clear and, in 

 the bed of the Httle brook about a mile south of Marsh pond, the 

 rock is considerably broken as a result of earth movements. The 

 topography suggests a moderate downthrow on the east, but instead 

 of being a true fault this may be simply a zone of excessive joint- 

 ing with little displacement. 



Alder brook and Trout brook faults. That Alder brook and 

 Trout brook follow fault zones for several miles as shown on the 

 map' is quite certain. Not only are these valleys narrow and 

 remarkably straight, but they have been cut into granite at right 

 angles to its structure. Such could scarcely be the case unless the 

 positions of the valleys were determined by zones of weakness due 

 to faulting. Further, the earth block between these two streams is 

 very distinctly depressed below the country immediately on either 

 side. The evidence, then, renders quite certain the existence of a 

 fault block from 1^2 to nearly 3 miles wide and several miles long 

 which has sunk between two faults, one along Alder brook and the 

 other along Trout brook. The topographic influence of this sunken 

 fault block is particularly striking in its southern half where the 

 Pine-Green hill mass on the east and the Oliver-Snyder hill mass 

 on the west each rise hundreds of feet very abruptly. Direct evi- 

 dence for the faulting from ledges along the fracture lines or zones 

 is wholly wanting, not a single outcrop occurring on either of the 

 brooks. The Alder brook fault continues for several miles south 

 into the North Creek quadrangle (see North Creek geologic map). 



Minerva stream fault. As regards both length and topographic 

 influence, this fault takes rank as one of the most prominent known 

 lines of fracture in the eastern Adirondacks. On the accompany- 

 ing map it shows a length of 125^ miles. It continues southward 

 for 6^ miles across the northwestern part of the North Creek 

 quadrangle and thence for at least 3 miles into the Thirteenth 

 Lake quadrangle. Its total length is, therefore, at least 22 miles. 

 Its topographic influence is very striking since a deep, usually 

 narrow, nearly straight valley has been cut out along this zone of 

 weakness along its whole course of over 12 miles in the Schroon 



