GENERAL STRATIGRAPHY OF THE REGION. 
UPPER WASHINGTON LIMESTONE. 
75 
The Upper TV ashington limestone, the top member of the Washing¬ 
ton formation, is the most important guide rock above the Wash¬ 
ington coal, from which it maintains a fairly constant distance of 
105 feet. It is a heavy and persistent limestone bed, having two or 
three characteristic layers that render its identification easy. It 
appears in outcrop at few places in the Burgettstown quadrangle, 
but is generally exposed over the entire area of the Claysville quad¬ 
rangle. This bed is thickest in the vicinity of Washington, where 
it consists of ten to twelve layers of limestone varying from a few 
inches to 3 feet in thickness and separated by partings of shale. The 
lowest layer of this bed is a rusty-brown limestone from 1 to 2 feet 
thick, which, on fresh fracture, is of a dark steel-gray color and * 
shows numerous tiny crystals of calcite. The next three or four 
layers are nearly identical in general appearance. They have a total 
thickness of 6 to 7 feet, are of dark to reddish-brown color, 
very hard and tough, and of irregular fracture, and some of the 
layers have numerous calcite crystals. They generally weather to a 
rusty cream color, though a small layer toward the bottom of this 
group weathers locally to a light reddish yellow. Above this group 
is a hard, thin-bedded, dark-brown limestone from 8 inches to 2 
feet in thickness. It is argillaceous in places, breaks rather easily 
with an uneven fracture, and weathers to a rusty cream color. This is 
the only layer in the lower portion of the Upper Washington lime¬ 
stone that may be easily recognized, and is one of the important 
markers of the member. The weathered surface of this rock has a 
rough, finely striated, filelike appearance, by which, when it has 
once been identified in the field, it may be recognized at a glance. 
From 3 to 5 inches of coarse brown shale separates this layer from the 
one above, which is a dark reddish-brown limestone in two beds 
having a total thickness of about 2^ feet. It is very hard and tough 
and weathers a rusty cream color. The face of a fractured portion 
of this limestone presents a crimped appearance around the edges. 
Above these layers is from G to 8 inches of coarse black shale. The 
next limestone above is dark gray, very hard, and somewhat clierty, 
and breaks easily under the hammer into small cubical blocks. 
T round Washington this layer is one of the thickest in the bed, being 
from 2^ to 3 feet in thickness. It is, however, variable both in quality 
and quantity, and in many localities is wanting. Overlying this 
limestone .is from 3 to G inches of coarse black shale, which in the 
type locality around Washington directly underlies a few inches of 
thin-bedded sandstone. In various portions of the Claysville quad¬ 
rangle this shale and sandstone appear to thicken greatly at the 
•expense of the underlying limestone. At a few places the shale was 
