Cushing — GrEOLOGy of Clinton County. 



553 



Plattsburgh. 



No pre-Cambrian rocks occur in Plattsburgli. 



Series TV. Potsdam sandstone. Except for the river exposures at 

 Cadyville just alluded to, the Potsdam does not outcrop in the township. In 

 fact, with this exception there is not an outcrop of any kind in the western 

 three-fourths of Plattsburgh. This wide belt must be underlaid in part 1>\ 

 rocks of Potsdam, in part by those of Calciferous age; but where the 

 boundary between them may lie is purely a matter of assumption. 



Calciferous sandrooh. By the Salmon river, at the bridge two miles 

 above the mouth, several ledges of a hard, dark blue, somewhat calcareous 



dolomite are exposed. By the road south of the liver a grey dolomite, with 

 seams and spheroids of calcite, is shown. Though no fossils w ere found, the 

 lithology of these outcrops puts them in the Calciferous, probably well 

 toward the top. 



At the pulp mill on the Saranac, three and one-half miles southwest of 

 Plattsburgh, the river is out of its old channel for a short distance, and 

 exposes a vertical section of some fifty feet, showing heavy, dark blue-grey 

 dolomites, which hold spheroids of calcite, and weather to a yellow color, 

 interstratified with dark calcarous slates. No fossils were found, and no other 



