GEOLOGY OF THE PORT LEYDEN QUADRANGLE 3 1 



The thickness of the Trenton has been approximately determined 

 m a number of places as follows : 



Feet 



Along Moose creek and Sugar river. 350 



Between Port Ley den and Locust Grove .-. 370 



Along Mill creek , 400 



Along House creek 450 



Along Roaring brook and Atwater creek 475 



Thus, in a distance of 20 miles across the map, from south to 

 north, the Trenton shows an increase in thickness of something 

 like 125 feet or at the rate of about 6 feet iper mile. Passing south- 

 eastwardly along the line of outcrop, the Trenton shows a progress- 

 ive thinning. Thus at Remsen it is about 300 feet ; near Middleville 

 200 feet; at Ingham Mills 100 feet; and at Canajoharie only 17 

 feet. Westward in Oswego county deep wells at Stillwater and 

 Central Square show respective thicknesses of 670 and 747 feet. 



Utica shale 



The Utica shale formation shows practically the same character- 

 istic features here as it does at its type locality at Utica. It is a 

 very fine grained, dark gray to black, thin bedded shale. The black 

 color is due to the presence of carbonaceous matter which may be 

 readily burnt out, although, contrary to a current popular idea, 

 nothing like a workable coal seam occurs within the formation 

 Occasionally some of the layers are rather sandy especially toward 

 the top. Toward the base of the formation some of the layers are 

 several inches thick and are frequently calcareous and except for 

 this the contact between the Utica and the Trenton is a sharp one. 

 Because of the softness of the rock and the character of the out- 

 crop, favorable to the development of talus slopes, the actual con- 

 tact between the shale and limestone was nowhere observed. Many 

 times, however, Trenton beds have been noted in such close prox- 

 imity to the shale that the boundary line can be pretty accurately 

 drawn. Such observations may be made along Atwater creek or 

 Moose creek. 



In spite of a considerable thickness its areal extent is rather 

 small because it outcrops along the base of the steep slope forming 

 the eastern fronts of Tug and Mohawk hills. Excellent sections 

 are to be found along all of the larger streams which cut across 

 this steep slope. Its broadest surface exposure is from Constable- 



