378 PRINCIPLES OF STRATIGRAPHY 



valley in Wyoming county to Morrisville in Madison county and 

 southward for an undetermined distance. Western New York is 

 free from salt, which was either not deposited, or was removed 

 by erosion during Upper Siluric time. 



Immediately above the red Vernon shales the salt is coarsely 

 crystallized, the crystals being commonly embedded in the mud. 

 Limestone, shale and gypsum occur as fragments mixed with the 

 clear salt crystals, the whole forming a brecciated mass. Sometimes 

 in the basal salt beds there is an abundance of layers and irregular 

 masses of shale and limestone, while in other localities the salt is 

 almost pure. At Livonia this basal layer is succeeded by 8 feet of 

 stratified marlyte grading upward into impure magnesian limestones, 

 both shales and limestones being full of seams and veins of salt, 

 often with columnar structure in the larger veins. Overlying the 

 limestone is the main salt bed. It is often very pure and well 

 stratified. Shaly matter and gypsum occur in thin streaks, but, on 

 the whole, the impurities are not more than two or three per cent, 

 of the entire bed. Non-continuous layers of limestone or shale 

 several inches thick sometimes occur. The crystals of salt are much 

 smaller than those of the mixed salt, and vary considerably in size 

 in the dififerent layers. The salt is again capped by a layer of mixed 

 salt like that found below. Gypsous shales are common here, these 

 containing more or less disseminated salt. Irregular and more per- 

 sistent layers of dark magnesian limestone also occur in the upper 

 part of the salt bed. They are up to two or three feet in thickness 

 and full of salt seams and grains, and have the appearance of having 

 been formed above the salt and of having settled down into it. The 

 roof of the salt bed likewise consists of large and small blocks of 

 gypsous shale, the spaces between the blocks, sometimes several 

 inches in width, being filled with salt. These salt veins sometimes 

 extend upward into the overlying rock for 200 feet, though, as a 

 rule, they are much shorter. 



The total thickness of the salt beds of central New York, in- 

 cluding the shale layers, ranges from 100 to 190 feet, but southward 

 it thickens to 470 feet, in the Ithaca well. The limestone layers in 

 this formation show evidence of exposure to the air during their 

 formation, by the abundance of mudcracks which are filled by salt, 

 gypsum or bhck mud. They are entirely unfossiliferous, as is this 

 whole series of deposits. 



The Camillus shales overlying the salt are gray, often containing 

 beds of magnesian limestone and great masses of gypsum, together 

 with some anhydrite. This gypsum has been regarded as an altera- 

 tion product, being formed from impure limestones of the water lime 



