r66 



NBW YORK STATE MUSEUM 



Iii the southeastern corner of the sheet, on the unnamed hill in 

 extreme northeast Dannemora, the Potsdam sandstone is found 

 at the greatest altitude vet noted for that formation in the 

 Adirondack region, This hill was erroneously mapped as gneiss 

 in the report on Clinton county in the loth annual report of the 

 New York state geologist. As it is difficult of access, and time 

 could not be taken to visit it, the topography, the altitude, and 

 the statements of guides were taken as the basis of the mapping. 

 ]>ut it seems unsafe to infer anything in Adirondack geology. 

 The ground must be gone over foot by foot. 



The hill breaks off in a cliff on the west side which looks like a 

 fault scarp. On the north and east at 1600 feet is a broad shelf 

 of bare, nearly horizontal sandstone, which is covered with blue- 

 berries and reproduces, on a small scale, the conditions on the 

 Flat rocks in Altona. Rock was found exposed on the hill up 

 to 1700 feet. The top is covered with morainic material but how 

 deeply is uncertain; the Potsdam certainly runs up to something 

 over 1700 feet however. A section of at least 200 feet in thick- 

 ness is comprised in the hillside. The occurrence of the rock 

 at this elevation is strongly suggestive of its former much 

 greater extent in the region. 



Passage beds. Between the Potsdam and the overlying lime- 

 stones is a zone, some 50 feet in thickness, of rapidly alternating 

 layers of pure white sandstone with all the lithologic characters 

 of the Potsdam, and gray, sandy, dolomitic limestone precisely 

 like the Calciferous above. These beds have been usually classed 

 with the Potsdam. The only exposures of these beds within the 

 limits of the sheet are in the northern part of Mooers township. 

 The geologic map of Canada shows Calciferous coming down to 

 the boundary at this point, but on the Xew York side of the line 

 there is no Calciferous exposed unless these passage beds are to 

 be counted such. 



Calciferous (Beekmantown) limestone. 1 Though rocks of this 



'Clark & Schuehert. Science. 10:874-78. The term, Beekmantown, is 

 much more suitable than the old name and should supersede it. The type 

 localities are just outside the limits of the sheet. 



