54 



Report of the State Geologist. 



NOTE 



Field Notes on the Geology of the Mohawlc Valley^ with a Ma]}, 



(From the Annual Report of the State Geologist for 1885, pp. 8-10.) 



At Little Falls there are two parallel faults extending 45° 

 east of north. One of these intersects the village and crosses 

 the New York Central railroad at the high stone wall built 

 up from the river at the lower end of the village. The same 

 fault crosses the West Shore railroad just above the deep cut 

 through the Labra^dorite, and this point is also occupied by an 

 extensive filling and stone wall built up from the river level.* 



The second iault forms the eastern termination of the escarp- 

 ment of gneiss and Calciferous below the village and is a mono- 

 clinal. 



Another monoclinal fault crosses the valley of the Mohawk 

 river above the mouth of East Canada creek and brings up the 

 Trenton limestone dipping to the west. 



An anticlinal fault occurs just above Fort Plain. The Calcif- 

 erous dips to the west, and across the line at Fort Plain the Birds- 

 eye limestone is found dipping to the southeast. Just below the 

 bridge at the last-mentioned locality is an exposure of Birdseye 

 limestone, which preserves the remains of former pot-holes at a 

 level of ten feet above the river, showing that at one time there 

 was a natural dam and fall at this point. 



From Fort Plain to the " Little Nose " the strata lie in a broad 

 synclinal with Canajoharie situated nearly in the center. 



Sections of the strata at Canajoharie and Spraker's Basin are 

 presented and make an interesting comparison. 



Section along creek entering the Mohawk river at Canajo- 

 harie, N. Y. 



At Canajoharie the Calciferous is comparatively thin, bringing 

 up underlying beds of limestone as shown in this section. IJpon 

 the undulating and worn surface of the Calciferous there is a 

 very thin bed (1-3) of Trenton limestone without any intervening 



*The significance of the artificial structure mentioned may not be apparent at first sight. A line- 

 of fault is a line of weakness. The rocks along such lines are usually much broken and eroded ; and 

 the place of many faults in New York is indicated by lines of swamps, lake beds and river valleys. 

 At Little Falls the strata are nearly everywhere exposed, and only along the line of this fault has it 

 been necessary to fill in extensively and build secure foundations for the roadbeds. 



