22 BULLETIN OF THE NEW YORK STATE MUSEUM 



GEOLOGY OF THE SALT AND GYPSUM 



The salt of New York occurs almost exclusively in the 

 Salina Group or as it is also called the Onondaga Salt 

 Group of the Upper Silurian Period which was described 

 by Vanuxem as follows :* 



" This important group contains all the gypsum masses of 

 western New York, and furnishes all the salt water of the 

 salines of the counties of Onondaga and Cayuga. From 

 the point where the Niagara group terminates at the east, 

 it rests upon the Clinton group; and as the latter group 

 also comes to its end near the first district, it reposes there 

 upon the Frankfort slate, upon which it continues to near 

 the Hudson river. 



It forms a part of the high range on the south side of the 

 Mohawk; appearing at the north end of Otsego county, and 

 in Herkimer and Oneida, being its northern outcrop. It 

 makes its first appearance by the side of the Erie canal at 

 the east end of Madison county, and from thence west the 

 canal was excavated in the group. 



The Onondaga salt group may be divided into four de- 

 posits. There are no well defined lines of division between 

 the deposits; but for practical purposes the divisions are 

 sufficiently obvious. 



The first or lowest deposit is the red shale, showing green 

 spots at the upper part of the mass. 2d, The lower gyp- 

 seous shales, the lower part alternating with the red shale, 

 which ceases with this mass. 3d, The gypseous deposit, 

 which embraces the great masses quarried for plaster, con- 

 sisting of two ranges, between which are the hopper-shaped 

 cavities, the vermicular limerock of Eaton, and other porous 

 rocks. 4th and lastly, Those rocks which show groups of 

 needle-form cavities placed side by side, caused by the 

 crystallization of sulphate of magnesia, f and which may 

 from that circumstance be called the magnesian deposit. 



* Report on the Geology of the 3rd District of N. Y. 

 f Sulphate of lime most probably. 



