44 
OIL AND GAS; OHIO, WtfST VIRGINIA, PENNSYLVANIA. 
of the Conemaugh formation. The top of the Big Dunkard, or 
lower sand rock, is about 425 feet below the Pittsburg coal. 
Next below the Big Dunkard is a sand 35 to 100 feet thick that has 
produced gas in different parts of the quadrangle, and is named by 
the drillers and operators the “ Gas ” sand. Its geologic position is 
in the Allegheny formation, and it probably corresponds with the 
Homewood sandstone. The average distance of the top of this sand 
below the Pittsburg coal is about 000 feet. 
The next lower sand is the Salt sand of the Pottsville formation. 
This bed lies at a distance of about 840 feet below the Pittsburg 
coal. It is a white sand and a gas producer in most of the geo¬ 
logically high localities; at other places it is saturated with salt 
water. This sand is always cased off' in wells which are drilled to 
the lower sands. At the base of the Salt sand is the unconformity 
already noted (p. 15). 
Below this unconformity and above the Big Injun sand are usually 
found two limestones and an intervening sand. These are known to 
the drillers as the Little and Big lime and the Keener sand. They 
belong to the Mauch Chunk formation and represent the Greenbrier 
limestone. 
At the base of the Big lime is the Big Injun sand. This is a 
heavy sandstone stratum ranging from 150 to more than 200 feet 
in thickness, in which the sands are of different colors and of differ¬ 
ent degrees of coarseness. The top of this sand is about 1,050 feet 
below the base of the Pittsburg coal. At about 1,340 feet below the 
Pittsburg coal and a short distance below the base of the Big Injun 
sand is a sand 20 to 35 feet thick, called by the drilling fraternity 
the “ Squaw ” sand. This sand has shown indications of oil in differ¬ 
ent places within the Burgettstown quadrangle, but so far has fur¬ 
nished no productive wells. 
At a distance of 1,480 to 1,520 feet below the Pittsburg coal a small 
sand is often found, heavily charged with salt water and called the 
Bitter Rock. Between 1,600 and 1,700 feet below the Pittsburg coal 
lies the Berea sand of Ohio, but in this area it consists almost entirely 
of closely cemented hard shells called the Thirty-foot shells. From 
90 to 100 feet below the Thirty-foot shells is the “ red rock.” This 
is not a sandstone, but a shale, and is generally noted by the drillers 
on account of its red color. Almost exactly 100 feet below the top 
of the u red rock is the top of the Hundred-foot oil sand. This is 
the most prolific sand ol the Burgettstown quadrangle, and its upper 
surface is represented by the red contours on the map (PI. IX). Its 
distance below the Pittsburg coal in different parts of the quadrangle 
is shown by the isochor lines on the convergence sheet. The Hun¬ 
dred-foot sand and those above it, up to and including the Big Injun 
