GEOLOGY OF THE PORT LEYDEN QUADRANGLE 



29 



within the quadrangle. In a general way the Trenton here shows 

 most of the features of the type locality. At Trenton Falls the 

 formation is about 300 feet thick and the rocks are mostly thin 

 bedded, impure, dark limestones with pronounced shale partings, 

 except the upper 30 feet which are thicker bedded, gray, crystalline 

 limestones. The following section shows that a marked lithologic 

 change has taken place in passing from Trenton Falls to Port 

 Leyden. 



Thick bedded, coarse crystalline, gray limestone 



Fairly thick bedded, gray, crystalline limestone 



Very thin bedded, dark limestone with thin shale 

 partings 



Thick bedded, coarse crystalline, gray limestone 

 Fairly thick bedded crystalline, gray limestone 



Thin bedded, dark limestone with thin shale partings 



Thick, gray, crystalline limestone beds 



Alternating, thin bedded, black limestone and shale 



Fig. I Columnar section from base to summit of the Trenton limestone formation along 

 Sugar river and Moose creek. The section is 350 feet thick. 



More than half of the section is here made up of the gray, 

 crystalline, heavy beds as opposed to only about 30 feet of such 

 beds at Trenton Falls. Within the Little Falls quadrangle the 

 heavy, crystalline beds are absent altogether, the upper Trenton 

 being represented by the Dolgeville shales which are in reality 

 alternating thin beds of impure limestone and shales. These and 



