8 



NEW YORK STATE MUSEUM 



UPPER SILURIC 



Salina beds 



. Camillus shale 



The lowest formation exposed within the limits of the quad- 

 rangle is the Camillus shale, which is the surface rock over an 

 area of 35 square miles north of Buffalo and Williamsville. 



It is entirely covered by drift on the American side of Niagara 

 river excepting a small outcrop at the extreme south end of Grand 

 island. On the Canadian side the upper beds are exposed in the 

 low cliffs along the river from a point opposite Strawberry island 

 almost to the International bridge. 



The rock at these exposures is mostly soft, light gray or olive 

 gypseous shale; a few thin layers are harder and more blocky in 

 structure. 



About 75 feet of Camillus shale come to the rock surface on this 

 quadrangle but these do not represent the entire formation. Its 

 precise thickness here is not known, but well cores show that beds 

 of gypsum, thinner and less pure toward the bottom, occur at 

 intervals through 150 feet or more of strata. 



The Vernon red shales that underlie the Camillus shale in the 

 central part of the State have not been recognized in the deep 

 borings about Buffalo, and if the Camillus formation is to here 

 include all of the strata between the Guelph dolomite of the 

 Niagaran group beneath, and the Bertie waterlime above, its 

 average thickness as shown in 10 wells is 333 feet. 



Gypsum and plaster have been mined in the Camillus shale in 

 Genesee, Monroe, Ontario, Seneca, Cayuga and Onondaga counties 

 in very large quantities but thus far no fossils have been found in 

 these beds in the western part of the State. The little brackish 

 water crustacean Leperditia alta occurs below the upper 

 gypsum bed in Onondaga county. 



Bertie waterlime 



The passage from the Camillus shale to the succeeding forma- 

 tion is a gradual one, the gypsum slowly diminishing in quantity 

 and the rock becoming much harder and, by the addition of alumina 

 and carbonate of magnesia, highly dolomitic. The Bertie water- 

 lime is usually in layers from a few inches to 2 to 3 feet thick, separ- 

 ated by thin seams of carbonaceous matter. Though very dark 

 when fresh the rock weathers to a light brown or buff. 



The proportion of calcareous matter varies considerably in the 

 different layers, the composition of many of them being such as to 

 make true hydraulic limestone or "cement rock." A bed of this 



