3^ ' NEW YORK STATE MUSEUM 



Seneca county 



The area in Seneca county covered by the SaUna shales lies in 

 the townships of Junius and Tyre with a small outcrop in the town 

 O'f Seneca Falls. In the two former townships outcrops are rare. 

 The soft character of the A'ernon and Camillus shales rendered 

 th-em susceptible to speedy erosion during the glacial period and 

 there has been formed a broad shallow east-west depression bounded 

 by the more resistant limestones on the north and south. This area 

 is heavily blanketed with glacial deposits, kames, drumlins etc. and 

 is frequently marshy. It is almost devoid of rock exposures. 

 Where the Seneca river has cut its channel through the Cobleskill 

 and Bertie waterlimes, however, the Camillus s'hales have been un- 

 covered and their gypsum masses exposed. The Camillus shale 

 series according to Luther^ " is composed in the lower part of thin 

 dolomitic limestones and thin layers of soft shale and at the top 

 has a bed of gypseous sihale 35 feet thick, some parts of which are 

 of sufficient purity to have, when pulverized, some economic value 

 as land plaster and wall plaster. Gypsum was quarried about 1840 

 near Black brook west of Nichols corners and the bed has been 

 penetrated in wells of that vicinity. It is not exposed along that 

 stream now." 



The exposures of gypsum along the Seneca river have been de- 

 scribed by John Delafield,^ as follows : '" The greatest exposures of 

 the rock are on the north bank, on the farm of Mr Frederick Swaby, 

 and also on the ground of Mr Cady. The rock on Mr Swaby's 

 farm was extensively worked at one period, and before 'he pur- 

 chased the property; but, owing in some degree to the limited size 

 of the beds, but chiefly to the neglect of the parties whO' worked 

 the quarries, they are not productive. The difficulty seems to 

 have arisen from the omission of separating the rock from the 

 shales and marly limestone which surrounds it. . . The hight 

 of the cutting is about 40 feet and the upper bed of rock, the drab 

 colored limestone (Bertie n'oterlime) is covered by a few feet of 

 soil ; it is about 6 feet thick." 



He speaks of the plaster as occurring in large unconnected masses 

 in the shale, one being 15 feet high and 35 feet broad. Gypsum 

 occurs on the south side of the river in the bluffs but is not ex- 

 posed. It is again exposed farther east on the north side of the 

 river at the railroad bridge; and it was uncovered on the south 



1 N. Y. State Mus. Bui. 128. 1909. p. 7. 



2 N. Y. State Agric. Soc. Trans, for 1850. 1851. 10:441-42, 



