SENECA COUNTY. 
449 
SENECA COUNTY. 
All that part of the county north of the Seneca lake outlet, with the exception of a small 
portion south of a line drawn from Waterloo in a northwest direction to Ontario county, is 
occupied by the Onondaga salt group. Nearly all this northern part of the county is deeply 
covered with alluvium ; and the rocks appear at very few points. One of these is in the bank 
of Bear creek, where gypsum was quarried many years since; and another about three miles 
north of Seneca-falls, where gypsum and gypseous marl were penetrated in digging a well. 
The great depth at which gypsum is found in the north part of the county will, for the pre¬ 
sent, and for a long time to come, preclude its profitable exploration. The waters of Seneca 
lake, which have worn a recent outlet along the southern limit of this series, expose the gyp¬ 
sum and associated rocks near Seneca-falls village, and for nearly three miles below. Along 
this distance the gypsum is extensively quarried. It occurs in irregular, often conical masses, 
enclosed in a greyish friable marl, with which it is often much intermixed, and in consequence 
deteriorated in quality. 
There is here no evidence that the masses of gypsum have forced up the strata, as noticed in 
some places in Monroe and Ontario counties. On the other hand, the lines of stratification in 
the marl are continued through the mass of gypsum without interruption. The strata are 
undulated, the depressions being between the beds of gypsum ; and this appearance may 
have been caused either from the porous nature of the marl by which some of it has been 
dissolved and carried off, or from contraction, on drying of the mass between the gypsum 
beds. The latter, being a chemical compound, and the force of aggregation greater on 
becoming indurated, has contracted less than the surrounding marl; it consequently presents 
a slight convexity in the surface. In these beds all appearances prove that the gypsum was 
separated from the marl by chemical attraction, while each was in a fluid or semifluid state. 
Small particles and seams of gypsum still remain scattered through the surrounding mass, 
and it very appropriately receives the name of gypseous marl. 
The rocks belonging to this formation are already described ; they all bear much uniformity 
in character at different points, and are easily recognized, even when the gypsum is not pre¬ 
sent, by their argillaceous nature, and nearly uniform drab or ash color on exposure to 
weather. Some portions are harder and darker, or frequently green on first exposure. Owing 
to the usually soft nature of the strata, they have been removed from extensive tracts, and 
the space filled with alluvium from more northern rocks; this is particularly the case in 
Wayne, and the greater part of Monroe counties, as well as in Seneca and Ontario; and 
from this fact, a principal member of the series, the red shale, has been overlooked. 
Knowing the character of this rock, from examining other localities, we find evidence of its 
existence along the northern part of this formation from the color of the soil; but after much 
careful examination, I have not found a point between the Cayuga lake and Genesee river, 
where that rock is exposed. Near King’s corners, in the town of Butler, Wayne county, the 
[Geol. 4th Dist.] 57 
