ORISKANY SANDSTONE. 
147 
Water-lime, and more extensively the Onondaga salt group,, must have remained, exposed 
above the surface of the ocean, or forming its bed in situations beyond the reach of any de¬ 
tritus or deposition. The production of these four rocks, Pentamerus limestone, Delthyris 
shaly limestone , Encrinol, and Upper Pentamerus limestone, each marked by a distinct as¬ 
semblage of fossils, must have required a long period of time ; and we can scarcely conceive 
of a condition of the ocean which would continue so long free from deposits of some kind, 
even though at great depths or distance from land. Since the point of greatest development 
of these rocks is less than two hundred miles from where they entirely disappear, it is im¬ 
possible that if the Water-lime or Onondaga salt group formed the bed of the ocean, there 
should not have been some deposition made upon its surface, and which has subsequently 
been removed. 
The evidence of shrinkage cracks in the upper part of the Salt group is a more prominent 
character in the eastern part of the State, where the rocks in question are well developed, than 
in the western part. Still in both places they exist, and are proof of the exposure of the sur¬ 
face above water. If we are unwilling to admit of this denudation to a considerable degree, 
we shall be forced to conclude that the Onondaga salt group was elevated above the ocean, 
and formed dry land, while the eastern portion was yet depressed below its surface, allowing 
the deposition of these limestones. 
Since also these formations are absent throughout the whole or a large portion of the wes¬ 
tern States, the same cause which operated here has also operated over this great extent, and 
we shall either admit a vast tract to have been elevated above the ocean, or that denudation 
has operated over this wide area. 
From all that we know, however, there seems not the least probability that all these rocks 
ever extended far westward ; for there is a gradual diminution of the material, as appears 
where the strata are exposed toward their westerly termination, and if the ocean covered all 
the surface beyond, the deposit has been so slight that subsequent operations have removed 
it. This seems the more probable conclusion, since we should expect to find evidence of the 
fact, had so large a surface remained above the ocean during this period. 
One of the most characteristic features of the Oriskany sandstone, is the abundance of small 
cavities which have been formed by the destruction of fossils. These present themselves in 
all cases where the rock is well developed. The porous nature of the mass has admitted the 
percolation of water, which has dissolved the calcareous matter of the shells, usually leaving 
casts of their internal structure. Where free from organic remains, it forms a fire stone of 
approved quality. 
This sandstone is well known in Pennsylvania and Virginia, constituting an important for¬ 
mation; and according to Prof. H. D. Rogers,* it is seven hundred feet thick in the former 
State. In New-York its greatest thickness is not more than thirty feet, and usually much less. 
Geological Report, 1838, p. 51. 
19* 
