Luther — Geology of the Salt District. 



205 



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of Onondaga county, where the limestones are very dark and bituminous and 

 less than ten feet thick. The shales are so heavily covered by drift that their 

 thickness is not known. 



The limestone appears occasionally in Mad- 

 son and Oneida counties and in the valley of the 

 Mohawk river, south of the village of Mohawk, 

 Herkimer county. It reappears as a thin layer 

 known as the Coralline limestone, in the Scho- 

 harie creek, near the foot of the Helderberg 

 mountains. 



The Niagara is a moderately deep sea forma- 

 tion, and no traces of salt have been found in it. 

 The deposition of its calcareous silts was sud- 

 denly brought to a close by a change in condition 

 of the sea and sedimentation of a different char- 

 acter began a new epoch . 



The Salina or Salt group. This embraces 

 beds of shales, limestones, rock salt and gypsum. 



Next above the Lockport limestone is a thick 

 bed of soft shales, bluish -grey, green and red, and 

 bearing at some exposures a strong resemblance 

 to the Medina shales, called on account of the 

 predominating color, the Salina Red shales. 

 They are best exposed in the vicinity of the Erie 

 canal in Madison, Onondaga and Cayuga counties, 

 and as far west as the Genesee river. They are 

 generally buried under heavy drift deposits in 

 the western part of the state, but are found in 

 all of the drilled wells sunk through that horizon 

 In the western counties some thin limestones are 

 intercalated with the shales, and the latter lose 

 to a large degree, the red color and become bluish 

 grey or olive green, but still presenting the banded 

 or variegated appearance observed in Onondaga 

 county. In texture, the shales are soft and brittle, 

 and on exposure rapidly turn to tough greasy clay. 

 Occasional thin layers are slightly arenaceous, 

 and in Onondaga county occur one or two layers of white and red sandstones, 

 a few inches thick, very similar in character to the Medina sandstones. 



w\ » svo n e 



Figure 3. Diagram showing rocks exposed 

 in central and western part of the salt dis- 

 trict, from lake Ontario to the Helderberg es- 

 carpment. 



