Faulted Region of the Mohawk. 



55 



formations. The limestone is followed by the Utica slate, which 

 is well developed. 



At Spraker's Basin the Calciferous is quite extensive, forming 

 the major part of the section, and is followed by a thin bed of 

 limestone, which represents the Chazy limestone. Following this 

 is the Trenton limestone, reaching a thickness of from ten to fif- 

 teen feet. 



Section along creek entering the Mohawk river at Spraker's 

 Basin, N. Y. 



Between Spraker's Basin and Randall there is a very marked 

 anticlinal fault, bringino: up the gneiss in the bed of the river and 

 giving origin to the " Noses." On the east side of the fault the. 

 gneiss is found more than 150 feet above the river, rising as high 

 as the Calciferous does on the opposite side of the fault line. 



Near the eastern line of this fault there is a cutting on the 

 West Shore railroad, at a point known as the " Little Nose," 

 through the gneiss and Calciferous, showing the line of junction 

 between these formations. This absolute line of junction is very 

 interesting, geologically, on account of the great rarity of such 

 exposures. 



The interval from the gneiss to the Calciferous represents the 

 Huronian, Primordial and Potsdam, and is, comparatively speak- 

 ing, one of great duration. These formations, represented else- 

 where by many thousand feet of sediments, are here represented 

 by from a few inches to several feet of breccia and loose chloritic 

 and ferruginous material 



The material occupying this interval is derived from the 

 decomposition of the gneiss and from some slight sedimentation, 

 and contains a small per cent, of gold and silver, and is the first 

 authenticated discovery of these minerals in the Mohawk valley. 

 The amount of the metals is much too small to be of any particu- 

 lar importance, but their occurrence is an interesting geological 

 fact. 



Following this loose material is a bed of breccia of variable 

 thickness carrying fragments of crystalline limestone and Pots- 

 dam sandstone. 



