DESCRIPTIOX OF FORMATIOXS IN ASCENDING ORDER 

 FROM NORTH TO SOUTH 



SILURIC 



CAMILLUS SHALE 



The lowest in the series of rock formations shown on the map 

 is the Camilkis member of the Cayugan group, 250 to 300 feet 

 thick, composed mainly of soft, light gray marlytes or gypseous 

 shales with frequent thin layers of hard dolomite or magnesian 

 limestone. 



The great deposit of rock salt that underlies all southern-central 

 and western New York is at or near the bottom of this formation 

 and the gypsum beds of equal commercial importance, so extensively 

 quarried in Onondaga county and westward to Genesee county, are 

 found in the upper part. It is said that the first discovery of 

 gypsum in the United States was made in 1792 in these beds at 

 Camillus, Onondaga county, when the principal g^^psum layer and a 

 large part of the formation were abundantly exposed. The name 

 of the formation is derived from this locality. 



The Camillus beds are generally barren of fossils though one or 

 more of the thin dolomites in the upper part contain at some locali- 

 ties the crustacean Leperditia scalaris? Jones, and one 

 or two other obscure forms. 



No exposures of this formation occur on these quadrangles but 

 the gypsum is mined at Oakfield and Alabama, and the upper part 

 of the formation outcrops in the banks of Tonawanda creek below 

 Indian Falls, on the quadrangles next north of these. 



BERTIE WATEELIME 



In the upper part of the Camillus beds there is an alternation 

 of shales and limestones in which the shales lose much of their 

 gypsum and the limest^^nes become more compact and heavier and 

 also, by the increase*' proportion of magnesia carbonate, highly 

 dolomitic. These pa?- ^age beds are succeeded by about 50 feet of 

 waterlime, dark coIo' jd when fresh but weathering to a light gray, 

 in layers from a fe> inches to 3 or 4 feet thick, separated by thin 

 seams of black caj oonaceous matter. The rock in some of the 

 layers is quite com )act and the lines of deposition are barely dis- 

 cernible, while othtr layers have a laminated structure or, in small 

 proportion to the entire mass, are more or less shaly. 



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