GEOLOGY OF THE SALT AND GYPSUM 23 



The whole of these deposits are found between Oneida 

 creek and Cayuga lake. To the east of the creek, they do 

 not all occur, as will subsequently be made known. They 

 thin out to the eastward and probably terminate entirely 

 a few miles east of the Hudson river; from which point 

 their thickness gradually increases towards the west, and 

 reaches its maximum in the counties of Onondaga and 

 Cayuga, where it is not less than seven hundred feet. The 

 gypsum has not been seen east of the western part of Oneida 

 county. The red shale comes to its end at the east end of 

 Herkimer county; and the whole group is reduced, in the 

 Helderberg in Albany county to a few feet of light grey or 

 lavender-colored compact calcareous rock with pyrites, 

 separating the Frankfort portion of the Hudson river group 

 from the water-lime series." 



The outcrop of the Salina shales as shown on the ac- 

 companying map is copied from the geological map of New 

 York published in 1844. 



The red shale is fine grained, earthy in fracture and 

 without regular lines of division. It breaks or crumbles into 

 irregular fragments. This deposit is not found east of Her- 

 kimer County and varies in thickness from 100 to nearly 

 500 feet. The second member of the series consists of shale 

 and calcareous rock of a light green color intermingled with 

 a red shale at its lower part. But little gypsum occurs in 

 this member. The rock is extremely porous, easily pene- 

 trated by water and falls to pieces at once on exposure to 

 the air. The third or gypseous deposit, which is important 

 commercially on account of its plaster beds, is also the 

 horizon from which the brine springs of Onondaga, Cayuga 

 and Madison counties were supposed by Vanuxem to have 

 been derived. The mass of the deposit consists of rather 

 soft yellowish or brownish shale and slate, both argillaceous 

 and calcareous. It maybe called a gypseous marl. It falls 

 to pieces when exposed to the weather, breaking in a series 

 of joints nearly at right angles to each other which give the 



