GENERAL STRATIGRAPHY OF THE REGION. 
85 
hard impervious rock, which is often called the “limestone cap.” 
This term is somewhat misleading, for in no case can it be considered 
a limestone, although the cementing material may be in part cal¬ 
careous. This portion of the rock is hard to drill, and is brought to 
the surface by the bailer in flakes, some of which are nearly half an 
inch in diameter. Below the “ limestone cap ” the rock is soft and 
easy to drill, appearing as a pure white sand, which is known to the 
drillers as “ pay " sand. This sand may continue to the bottom of 
the bed, but in some places it grades downward into a hard white 
sand. The position of the “ pay ” sand varies somewhat from place to 
place. In some wells it occurs 6 to 12 feet from the top of the bed 
and in others 21 to 30 feet from the top. In still other wells no pay 
streak has been encountered, and the rock is a hard cemented sand 
from top to bottom. The thickness of the pay streak varies greatly. 
In some wells it is only a few inches to a foot in thickness and is 
divided by layers of hard rock. 
Over considerable areas the Berea sand is divided into two parts by 
a thin bed of shale. In such places the lower part is often spoken of 
as the “ second-pay ” sand, and in some wells it has been the source 
of valuable oil production. 
In eastern Ohio few wells have been drilled below the Berea sand, 
and consequently little is known regarding the presence or absence 
of lower sands, but in Pennsylvania the Berea is represented by the 
“ thirty-foot shells,” below which most of the oil-producing sands 
have been found. 
HUNDRED-FOOT SAND. 
The Hundred-foot sand is about 190 feet below the Berea sand and 
100 feet below the red shale. It is a gray sand of medium fineness, 
containing white quartz pebbles as large as small peas. It receives 
its name from its thickness in Butler County, Pa. 
GANTZ SAND. 
In parts of Washington and Greene counties the top part of the 
Hundred-foot sand is named the Gantz, and the sand below the first 
“ break ” is the Fifty-foot. It is probable that these two sands are 
together equivalent to the Hundred-foot. 
NINEVEH THIRTY-FOOT SAND. 
The position of the Hineveh Thirty-foot sand is 100 feet below the 
top of the Hundred-foot. It is gray in color and very fine grained. 
GORDON SAND. 
The Gordon sand is about 210 feet below the Hundred-fool:. It 
varies from a knife-edge to 60 feet in thickness in the Claysville 
