Faulted Region of the Mohawk. 37 



At the eastern entrance of the Little Falls gorge the crystalline 

 rocks and overlying Calciferous sandrock present a precipitous 

 front to the eastward. In a short distance to the south and to 

 the north this front becomes flanked by slopes of Utica slate 

 which rapidly rise to above the level of the upper surface of the 

 crystalline rocks. A short distance south of the river the Cal- 

 ciferous and Trenton dip beneath the Utica slate and the fault 

 is lost in the high hills of the Hudson river formation to the 

 southward. 



The actual fault plane is obscurely exposed at several points 

 on the north side of the river and if not vertical it is very, nearly 

 so. The shales in the adjoining slopes are bent up against the 

 fault at angles from 40°-70°, averaging 60° in greater part. This 

 steep eastward dip rapidly decreases to the east, and in exposures 

 a half mile below the mouth of the gorge a gentle southwest dip 

 is observed at several points near the river 



Xorthward from the river valley the presence of the fault is 

 marked by a cliff of Calciferous, rising to greater or less height 

 above the rounded hills of the Utica slate region eastward. 



Three miles north of the Mohawk the fault is crossed by a 

 small depression which cuts through the Calciferous and a short 

 distance into the crystalline rocks on the west side of the 

 fault, and through Utica, Trenton and Birdseye beds to the top 

 of the Calciferous on the east side. The relations at this point 

 are shown in longitudinal section in figure 3. The upturn of the 

 beds here is very moderate as the dips are not over 6°. The 

 actual fault plane is not exposed but there are outcrops 

 within a yard or two of it. At Little Falls there are no means 

 for estimating the amount of the uplift for we do not know the 

 thickness of strata lying against the thrown side of the fault. 

 At this locality the presence of the Trenton on both sides, and 

 the moderate dips, afford all necessary data. An estimate made 

 from fairly accordant aneroid readings with the estimated allow- 

 ance for dip, gave an average of 310 feet. 



On the north side of this depression the Utica slate lies against 

 the fault, with the usual cliff of Calciferous on the west side of 

 the uplift. A short distance west of the crest of the cliff are the 

 low terraces of Trenton limestone surmounted by rounded hills 

 of Utica slate. A mile and a half farther north the fault has 



