Bedrock Profile

A drainage divide at headwaters breaches the Waynesburg syncline, at Van Voorhis Hill it's highest point. The elevation ranges from 1320-1480 feet.

The Greene formation, the highest in the watershed, is composed of sandstone, siltstone, mudstone, and thin units of limestone, clay, carbonaceous shale, and coal. This formation is based at 1,340 feet above mean sea level. Most of the tributaries in the headwaters region begin in the Washington formation. The upper member of this formation is mainly limestone separated by clastic rock ranging in composition from mudstone to sandstone. The middle member is composed of, in descending order: mudstone and siltstone, sandstone, carbonaceous shale with thin impure coal at the base. The thickness of this layer is upwards of 145 feet.
The upper tributaries pass through lower Washington limestone members and begin to form a main stream channel in the middle and lower Waynesburg formation. The stream descends from an elevation of 1,160 feet to 1,040 feet. The middle member is composed of thin clay, siltstone with lenses of sandstone, thin coal, and siltstone with lenticular limestone, sandstone, and argillaceous limestone, in part detrital, generally in two multiple bedded units separated by siltstone and limestone, and Waynesburg "A" coal. The lower member is composed of clay, limestone, sandstone and the Waynesburg coal bed.
Less than a mile down stream, the channel enters the Uniontown formation. Composed in descending order, of clay, siltstone, and sandstone in the upper member. The lower member is composed of limestone, siltstone or mudstone, and the Uniontown coal bed. The thickness ranges from 70 feet - 90 feet.
Approximately one and one quarter miles downstream, the stream enters the upper member of the Pittsburgh formation, composed mainly of argillaceous limestone in alternating units of 3-6 beds. The main channel has an elevation at about 1,000 feet.
The main channel remains in the Pittsburgh formation, progressing from the upper member through the Sewickly member as it passes below the mine site. These formations are generally composed of alternating very argillaceous limestone, mudstone, and siltstone in the upper member, and mostly limestone in the Sewickly member.
The first significantly large tributary enters the stream just above Deem's Park from the north, and a smaller tributary enters just below the park from the south. In this area the channel has cut down to the lower member of the Pittsburgh formation. It remains in this member until it flows past Walkertown. The lower Pittsburgh member is composed mostly of mudstone that contains thin layers of siltstone and fine sandstone. The total relief through the Pittsburgh formation is approximately 100-120 feet.
At Walkertown the next large tributary, Little Pike Run enters the main channel. Here the main channel, as well as the lowest 0.75 miles of the tributary, has entered the Conemaugh formation. The stream remains in this formation for the last 4-5 miles of its journey to the Monogahela River. The formation consists of irregularly interbedded mudstone containing beds of siltstone and sandstone as much as 30 feet thick. The stream enters this last formation at an elevation of about 900 feet and descends to the Monogahela's normal pool level of 738 feet at Coal Center.
Other tributaries enter from the north at Daisytown from Hoods Hollow, and at Granville from Gorby Run Hollow. These tributaries reside mostly in the lower Pittsburgh and Conemaugh formations. (R. Vargo)