68 
OIL AND GAS; OHIO, WEST VIRGINIA, PENNSYLVANIA. 
down to the lowest oil sand concerning which reliable information 
has been obtained. The reason for thus commencing in the middle 
and going in both directions is that the Pittsburg coal, at the base of 
the Monongahela formation, is well known by all oil operators and 
engineers of the region and has long been used by them as a datum 
plane. 
FORMATIONS ABOVE THE PITTSBURG COAL- 
MONONGAHELA FORMATION. 
The rocks from the base of the Pittsburg coal to the top of the 
Waynesburg coal are included in the Monongahela formation. This 
is one of the most important formations in the quadrangle, not only 
as to area covered, which includes the greater part of the surface of 
the two northern quadrangles, but also as to economic value. Eco¬ 
nomically the more important members of this formation are the 
Pittsburg coal, Benwood limestone, and Waynesburg coal. 
PITTSBURG COAL AND ASSOCIATED ROCKS. 
The important coal bed, known as the Pittsburg coal, lies at the 
base of the Monongahela formation. It is the most persistent coal 
bed known in the Appalachian field, covering much of southwestern 
Pennsylvania, eastern Ohio, and northern West Virginia. 
In the three quadrangles considered the bed maintains a thickness 
of nearly 5 feet of workable, coal. It is divided into four, and 
locally into five, benches by thin partings of clay or shale. 
The conditions above the Pittsburg coal differ materially in differ¬ 
ent portions of the area investigated. In the eastern half of the 
Burgettstown quadrangle the upper division of the Pittsburg coal 
is present, consisting of alternate bands 6 or 8 inches in thickness 
of shale and coal which extend for a distance of 7 or 8 feet above the 
main bed. 
In the northern part of the Burgettstown quadrangle and over 
most of the Steubenville quadrangle the main Pittsburg coal is over- 
lain by shale and a bed of dark-blue limestone 1 to 2 feet thick, the 
top of which is from 8 to 20 feet above the base of the main coal bed. 
Above the limestone is a coal bed from 6 inches to 2 feet in thickness. 
This is known as the Pittsburg Rider or Rooster seam. 
In the western part of the Burgettstown quadrangle and the east¬ 
ern part of the Steubenville quadrangle the upper division of the 
Pittsburg coal and the rocks described above are replaced by the 
Pittsburg sandstone. This is a medium-grained brown sandstone 
from 12 to 80 feet in thickness. It has the appearance of being a 
fair building stone. 
