— 
1884. ] 497 [Clay pole, 
Tar ONONDAGA SALT Group, oR Gypstous Groupe oF New YORK, IN 
Perry County, Pa. 
Having thus, in appearance, satisfactorily placed the lower portion of 
Rogers’ fifth group on the horizon of the Clinton of New York, I proceed 
to consider its upper portion. 
This, in the district under consideration, consists of a vast mass of shales 
with almost no variation, except that caused by a few thin layers of sand- 
stone. These shales are red at base, but graduate upward with gray beds, 
the red color disappearing as we ascend through the series. The lower or 
red portion is about 700 feet thick, and the upper or gray portion about 150 
or 200 feet. These are separated by about 700 feet of what have been 
called the variegated shales, consisting of alternate beds of red, green and 
ashen-gray color with a few interbedded sandstones. 
It would be of course natural to correlate this shale with the limestone 
immediately overlying the Clinton in New York, but for reasons, which 
will appear presently, I have preferred to make it the equivalent of the 
Onondaga group of New York, which immediately overlies the Niagara, 
and thus to leave the latter unrepresented in Perry county. 
STRATIGRAPHICAL AND LITHOLOGICAL EVIDENCE. 
The Onondaga group of New York consists, like that just described, of a 
mass of variegated shales, and, as some of its names imply, it there yields 
salt and gypsum. Its total thickness, given by Vanuxem in the Report of 
the Third District, is about 700 feet, and it is divided as shown below. 
The section in Perry county is given in another column for comparison. 
New York. Perry County, Pa. 
Magnesian rock == Limestone with 
Stylolites. 
Gypseous bed (upper). 
Porous (vermicular) limerock. Gray, calcareous marl. 
Gypseous bed (lower). 
Variegated shale (red and green). Variegated shale (red 
and green). 
Red shale, Red shale. 
Thickness 700 feet. Thickness 1600 feet. 
. Very close correspondence exists between the beds at the two places. 
At both they consist, at base, of a thick mass of red shale. At both, 
overlying the red shale is another mass of varying color. At both, these 
two beds form the bulk of the group. So closely do the two sections re- 
semble one another, that the description given of these lower beds in New 
York may be copied and applied literally to those in Perry county. 
Mr. Vanuxem says (Report on Third District of New York, p. 96) of 
the red shale : 
“The great mass is of a blood-red color, fine-grained, earthy in fracture, 
breaking or crumbling into irregular fragments.’’ 
PROC. AMER. PHILOS. soc. xxt. 115. 83K. PRINTED JUNE 5, 1884. 
