GENERAL STRATIGRAPHY OF THE REGION. 
69 
REDSTONE COAL. 
In a portion of the Burgettstown quadrangle the Redstone coal, a 
few inches in thickness, occurs 60 to TO feet above the base of the 
Pittsburg coal. It is underlain by an easily disintegrating lime¬ 
stone. The coal is not present, however, over most of the area 
investigated. 
SEWICKLEY COAL. 
The Sewickley coal, which is equivalent to the Meigs Creek coal of 
Ohio, is only 4 to 8 inches thick in the Burgettstown quadrangle and 
the eastern part of the Steubenville quadrangle. In the western and 
southern parts of the Steubenville quadrangle it increases in thick¬ 
ness to more than 2 feet and appears to be of good quality. The 
interval separating the Sewickley coal from the Pittsburg Rider 
coal is occupied by an unbroken deposit of shale TO feet thick, locally 
rather sandy, especially in the lower portion. 
ROCKS BETWEEN SEWICKLEY AND UNIONTOWN COAL BEDS. 
General description .—The rocks lying above the Sewickley and 
below the Uniontown coal are generally calcareous. In the early 
surveys of Pennsylvania this bed was called the “ Great ” limestone 
on account of its thickness (150 feet), which is unusual for a lime¬ 
stone bed in the coal-bearing rocks. Later it has been called the 
Benwood limestone, from the town of Benwood, W. Ya., a short dis¬ 
tance below Wheeling. In the area investigated this portion of the 
Monongaliela has a thickness of about 100 feet and contains many 
beds of limestone, but they are not numerous enough to justify their 
grouping together into a distinct limestone member. 
Lowest beds .—The lowest few feet of these rocks consist of thinly 
bedded limestone, which on weathering breaks up into slabs of a 
cream-white color. The space between the beds is tilled with calca¬ 
reous shale. Above this limestone is calcareous shale, but in a few 
localities it is overlain by a massive layer of light-blue limestone 
about 7 or 8 feet thick, with a conchoidal fracture and a smooth sur¬ 
face. This bed is rather impure, containing much clay. It is not 
persistent and in many places its position is occupied by yellow shale. 
Dinsmore limestone .—About 35 feet above the Sewickley coal is a 
series of limestone beds which are so characteristic that they have 
been traced and identified through the entire area of the two northern 
quadrangles. For this reason they are considered as an independent 
member of the Monongaliela formation and are named from the town 
of Dinsmore, Washington County, Pa. The total thickness of this 
member is about 4 feet. It is composed of a number of cream-white 
limestone beds from 4 to 8 inches in thickness. The spaces between 
the beds are filled with calcareous shale, which generally weathers out 
