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NEW YORK STATE MUSEUM 



SILURIC 



Camillus shale 



This term has been applied to the gypseous shales lying above the^ 

 horizon of the salt and forming one of the stratigraphic integers of 

 the Salina group. It is the lowest formation represented on the map 

 and only the upper portion of the shales to a thickness of about 40 

 feet is here exposed. The rock is a soft, dark gray shale containing a 

 varying proportion of gypsum, usually in thin uneven seams or 

 lenses. It is abundantly exposed and has been extensively quarried 

 in the towns of Camillus, Elbridge and DeWitt in Onondaga county, 

 Springport in Cayuga county and Phelps in Ontario county and is 

 commonly known as " piaster rock." Though it is present in this 

 area it has been excavated by erosion and then covered so deeply by 

 alluvial accumulations through the Onondaga valley that at no place 

 are the shales well displayed, and the estimate of its thickness as 

 given is based on data derived from adjoining regions. Farther 

 north in the town of DeWitt outside the boundary of this map, this 

 rock is much thicker and at about 100 feet below the top of these 

 shales, near the Heard quarries, there are some layers of limestone 

 which contain in considerable abundance the species L e p e r d i t i a 

 s c a 1 a r i s Jones. 



Bertie dolomite 



This division of the Salina group, taking its name from its ex- 

 posures in the township of Bertie, Ontario, is here composed of fine 

 dark gray waterlime weathering to light drab, with a brownish or 

 yellowish shade. At the base of the entire exposure which so far 

 as exposed and calculated, is about 15 feet thick, 11 feet are thinly 

 laminated. The upper stratum, 4 feet thick, is harder and but 

 slightly schistose. In the western part of the State the rock becomes 

 more compact and from it is quarried the very large amount of 

 waterlime cement manufactured at Akron and Buffalo. It is not 

 however used for that purpose in this vicinity, the heavier layers of 

 cement rock higher in the section being preferred. Exposures of 

 this formation are to be found along Butternut creek below James- 

 ville and this is the only place where the rock appears to advantage 



