Luther — Geology of the Salt District. 



213 



horizon, the upper layer thins out and conies to an end, while the lower one 

 appears to be changed in character and to have become ordinary limestone. 

 At Marcellus Falls, the water-lime layers reappear, the upper layer two 

 feet ten inches thick and the lower one five feet three inches with thirteen 

 inches of blue limestone between them. At Skaneateles Falls the beds have 

 practically coalesced and are nine feet six inches thick, including four inches 

 of blue shale in two layers. 



They are quarried at several localities in Cayuga county, and can be 

 easilv recognized at all of the exposurses of their horizon in the central 

 counties, but by reason of some difference in their composition they do 

 not make good cement in Ontario, Livingston and Genesee counties. 



AVater-limestone is extensively mined and quarried, however, at Akron, 

 Erie county, from a layer eight feet thick, that is separated from the " grey " 

 (Onondaga) limestone by about five feet of hard, tough, clayey, drab lime- 

 stone, known to the miners as " bullhead." 



On account of the presence of the water-lime layers, these upper and 

 purer limestones in which they are intercalated, have been collectively 

 designated the " Water-lime Group " and have sometimes been regarded as 

 constituting the upper division of the Salina period. As they are apparently 

 synchronous, and to some degree coextensive with the lower division of the 

 Lower Ilelderberg rocks of the eastern part of the state, and contain several 

 of the characteristic fossils of that formation, they have by some been termed 

 Lower Ilelderberg limestones, and are usually so designated in the shaft and 

 well records. 



Oriskany sandstone. In the eastern and central part of the salt district the 

 next formation in the order of superposition is the Oriskany sandstone. It 

 is composed of medium sized grains of nearly white quartz sand, having at 

 different localities a yellowish, pinkish or brownish shade. It is usually more 

 or less calcareous and very hard and firm, and suitable so far as durability 

 goes, for building purposes. At some exposures, however, it is quite soft and 

 friable. It is exceedingly variable in thickness. 



At Oriskany Falls, Oneida county, it is twenty feet thick in two or three 

 layers. Diminishing toward the west, it is but a few inches thick at Cazenovia, 

 Madison county. Across Onondaga county, it decreases and disappears at 

 Split Rock, then appears again and attains its greatest thickness in the salt 

 district, twenty-five to thirty feet, south of Skaneateles Junction. It diminishes 

 again toward the west, and at its last visible outcrop, in the village of Phelps, 

 it is two feet thick. 



