174 J. J. STEVENSON CARBONIFEROUS OF APPALACHIAN BASIN 



clay partings, is 11 feet 9 inches thick, with the Mahoning limestone 

 5 feet thick and 2 feet 6 inches below it. The Lower Mahoning is said 

 to be at least 75 feet thick. 



Westward from Blairsville the rocks come up along the Kiskiminitas 

 river (formed by union of the Conemaugh and Loyalhanna) and the 

 lower beds are reached toward the western border of the county, near 

 Salzburg, where the section is : 



Feet 



1. Red shale 



2. Sandstone [Buffalo] 100 



3. Sandy shale [black] 10 



4. Sandstone [Upper Mahoning] 50 



5. Coal bed [Upper Gallitzin] Trace 



6. Variegated shale 15 



7. Sandstone 15 



8. Coal bed [Lower Gallitzin] Trace 



9. Ferruginous limestone and ore [Mahoning] 



10. Shale 10 



11. Sandstone [Lower Mahoning] 20 



12. Slates 8 



to the Upper Freeport, giving 124 feet as the thickness of the Mahoning, 

 which is no longer wholly a massive sandstone as east from Blairsville. 

 Stevenson states that the shales Number 3 are dark and argillaceous, 

 carrying nodular ore which farther up the river becomes a continuous 

 layer; so that here one finds the Brush Creek limestone.* The sand- 

 stone Number 2 includes not only the Buffalo, which is between the Cam- 

 bridge and Brush Creek limestone, but also the Cowrun of Ohio, and 

 the red shale is evidently near the Barton horizon. This sandstone be- 

 comes less prominent northward and at 12 miles from Salzburg the 

 Brush Creek limestone was seen. That limestone was observed also 

 farther north on the Armstrong border, where Mr Piatt's section shows 

 coal streaks at 58, 73, 100, and 117 feet below, with a limestone, 4 feet, 

 underlying that at 73. The Upper Freeport is at only a few feet lower. f 

 The limestone is representative of the Mahoning and the four coal 

 streaks may be taken as illustrations of irregularities in subsidence and 

 deposition at the Gallitzin horizon. 



Armstrong county, west from Indiana, south from Clarion, and north 

 from Westmoreland, is divided by the i\llegheny river. East from that 

 stream the Conemaugh is for the most part the surface formation and 

 the Pittsburg coal bed is reached in the southeast corner. 



* J. J. Stevenson: (K 2), p. 318. 



t W. G. Piatt: (H 4), pp. 157, 170, 174, 244, 257, 270, 280, 284. 



