120 ECONOMIC GEOLOGY OF AMITY QUADRANGLE, PA. 
uniformly of a double composite bed; that is, it contains a lower and 
an upper member separated by a considerable thickness of shale, 
both members being in turn divided into a number of layers sepa- 
rated by thin beds of shale. 
At several points in the Amity quadrangle the Benwood is well 
exposed. In several ravines northeast of Kammerer, in eastern Not- 
tingham Township, and in Union Township, off the edge of the quad- 
rangle, the exposures are especially good. At one point, on a small 
run on the boundary of the quadrangle, in Union Township, the 
stream makes a perpendicular fall of 30 feet, caused by resistance to 
erosion of one of the limestone strata and the consequent undercut- 
ting of 25 feet of soft interstratified shales (PL VII, A). Similar 
falls, of less height, occur on several of the small streams in this vicin- 
ity. One of the best measured sections of this limestone is at the 
mouth of Brush Run, Peters Township, in the Carnegie quadrangle, 
as follows: 
Section of Benwood limestone <ii mouth of Brush Run, Peters Township.® 
Ft. in. 
Concealed 117 
Limestone 1 
Sandstone 5 
Limestone, brecciated 2 
Concealed 15 
Limestone 1 (> 
Sandstone II 
Concealed 15 
Shale 5 
Limestone 12 
Shale 12 
Limestone 50 
Shale, sandy, to creek 15 
A fair section of this limestone is also given in the record of the 
.Moses Smith diamond-drill hole, near Bissell (p. 16). Several oil and 
gas wells report the limestone, but such records are less reliable than 
surface measurements. 
In general, the Benwood limestone is considerably broken up by 
shale, as in the section just given, but a hard layer 30 to 50 feet thick 
near the bottom seems to be very persistent. The character of the 
limestone is variable. The "Uniontown" member, or upper portion, 
contains in many places 6 to 15 feet of an impure brownish to buff- 
colored limestone. The lower portion is generally a hard, pure lime- 
stone of light-brown to gray colocs. One thin stratum weathers very 
yellow, with a peculiar honeycombed appearance. The rock is in 
many places siliceous or argillaceous and in some ferruginous. The 
bottom portion is said to be generally the more magnesian, although 
all portions are high in magnesia, as indicated by the first three of the 
"Stevenson, J. J., Second Geol. Survey Pennsylvania, Rept. K, 1876, p. 226. 
