146 
GEOLOGY OF THE FOURTH DISTRICT. 
18. ORISKANY SANDSTONE.* 
(No. 7, of the Pennsylvania Survey.) 
This rock, where best developed in the Fourth District, is a coarse, rather loosely ce¬ 
mented, purely siliceous sandstone, of a yellowish white color. It contains some flattened 
nodules of chert or flint, and cavities lined with the same mineral, approaching in appearance 
to chalcedony. In the upper part of the rock are numerous concretions of dark-colored or 
nearly black compact crystalline sandstone, very hard and tough. These vary in size from 
an inch to five or six inches diameter ; their external character is much like boulders of some 
hard primary rock. 
In other localities in the district this rock is scarcely recognizable. In Monroe county, its 
only representative is a layer of greenish conglomerate about four inches thick. (See illus¬ 
tration No. 56.) It is composed of coarse sand and small pebbles, with some fragments of 
the light-colored argillaceous limestone derived from the next rock below. At one or two 
other points it appears as a coarse sandstone of a few inches in thickness, resting on the Onon¬ 
daga salt group. The last place in the district where it has been noticed is in the bed of 
Black creek at Morganville in Genesee county. 
The general absence in the district of the four last-named rocks, either from thinning out 
or from subsequent denudation, forms an interesting subject of inquiry. The Oriskany sand¬ 
stone seems to be deposited in depressions formed either from the natural inequalities in the 
surface of the previous rocks, or arising from denudation. The presence of worn fragments 
and pebbles of the argillaceous limestone of the salt group proves that denudation did take 
place after the latter rock had in some degree become indurated. 
Farther west where there is no representative of the Oriskany sandstone, the surface on 
which the higher limestones rest is very uneven, consisting of abrupt elevations and depres¬ 
sions very similar to the channelled bed of a powerful stream. There have, however, been 
no grooves or striae observed ; but since the appearances just noticed are usually seen in the 
face of cliffs, or in the sides of quarries, it is by no means certain that such marks do not exist. 
Should this fact once be established, it will open a vast field, both for observation and spe¬ 
culation. The absence of rocks, whether from thinning out, owing to want of material, or to 
removal since deposition, involves some interesting points of inquiry. 
In the present case, if the formations between the Water lime and the Oriskany sandstone, 
which appear in the eastern part of the State, have never been deposited in the west, then the 
* Oriskany. The aboriginal name ol this place is Areskana, signifying the residence of the God of war, and was a place 
where the. Aganousioni or United Braves held their war councils. 
For this information my readers are indebted to Giles F. Yates, Esq. of Schenectada, who has given much attention to 
the aboriginal names along the Mohawk valley. 
