50 ECONOMIC GEOLOGY OF AMITY QUADRANGLE, PA. 
occurring in the Conemaugh formation 480 to 540 feet below the Pitts- 
burg coal and 50 to 100 feet above the Upper Freeport coal. a It is 
frequently recorded as a double sand, in which case the upper and 
lower divisions are known as Little Dunkard and Big Dunkard, 
respectively. 
The Big Dunkard sand in many places lies almost directly on top 
of the Upper Freeport coal. It therefore corresponds in position with 
the Mahoning sandstone, which is one of the most conspicuous sand- 
stone lentils farther north and east in western Pennsylvania. The 
thickness of the Big Dunkard varies from 30 to 100 feet. Where sim- 
ply the Dunkard sand is recorded, the Big Dunkard is most commonly 
referred to, and this is believed to be the more persistent of the two 
beds. In sonic cases, however, the sand is thick enough to include 
both divisions. 
The top of the Little Dunkard sand usually occurs at 170 to 240 feet 
above the Upper Freeport coal, and this sand is therefore considered 
the equivalent of the Saltsburg sandstone, a lentil which forms a con- 
spicuous surface feature over large areas in the western part of the 
State. The thickness of the Little Dunkard is generally 20 to 40 feet. 
The name of these sands was taken from Dunkard Creek, near the 
mouth of which an oil pool was discovered in 1861. The Dunkard 
sand has produced oil in several places, but not in this quadrangle. 
Gas sand. — Several sands occur in the Allegheny formation. The 
principal bed recorded by the drillers is known as the Gas sand and lies 
near the middle of the formation, 070 to 840 feet below the Pittsburg 
coal. Although rather variable in position, it generally corresponds, 
where correctly noted, with the Kittanning sandstone, between the 
Upper and Lower Kittanning coals. In thickness this sand varies 
from 15 to 70 feet. A small quantity of gas is occasionally encountered 
in it. 
Salt sand. — The Salt sand corresponds to the Pottsville formation 
of northern and central Pennsylvania and occurs from 870 to 990 feet 
below the Pittsburg coal. It varies in thickness from 100 to 170 feet, 
but generally contains a break of shale near its center. This sand 
sometimes contains a little gas, but is otherwise unproductive. It is 
important to the drillers for the reason that it contains a large quan- 
tity of salt water. 
It should be noted that the Salt sand of this region occurs above the 
Big Injun, while in Armstrong County the same name is applied to a 
gas-bearing stratum below the Big Injun. 
Big Injun sand. — This is the name given by the drillers to a hard, 
fine-grained, gray sandstone, which occurs at the top of the Pocono 
formation, directly below the Big lime. It corresponds with the Bur- 
goon sandstone, which outcrops on the Allegheny Front, and is also 
i Unless otherwise stated, all intervals in this report arc from top to top of the respective beds. 
