46 J. J. STEVENSON LOWER CARBONIFEROUS, APPALACHIAN BASIN 



occurs chiefly in the sandstones and becomes more abundant^ north- 

 eastwardl3^ P. J. P. Lesley calls attention to the presence of calcareous 

 layers near Ashley, in the upper third of the section. f There is prac- 

 ticalh^ no information respecting the western extension of the southern 

 field beyond Professor Claypole's statement that the thickness of shale 

 spared from erosion is at least 1,500 feet in Perr}^ county, and that some 

 of the beds contain enough of calcareous matter to make well water 

 hard. J 



The Broad Top coal field may be regarded as in a line with the Northern 

 Anthracite field and the area in Fulton county as corresponding to the 

 Middle field. Onl}^ the lower portion of the Mauch Chunk remains in 

 the Fulton area, but the surface is littered with fragments of limestone, 

 always sand}^ sometimes red, often bluish. This is the most eastern 

 locality in Pennsylvania at which any of the limestones of the Mauch 

 Chunk are well defined. § The conditions around the Broad Top field 

 have been studied by I. C. White, Ashburner, and Stevenson. Ash- 

 burner's section on the eastern side within Huntingdon county showed 

 a thickness of 1,100 feet, thus : 



Feet 



Sandstone and shale 910 



Limestone 49 



Shale and sandstone 141 



The writer was inclined formerl}^ to regard the lowest member as be- 

 longing to the Pocono (Logan), but in view of the conditions along the 

 northern border, he now regards it as equivalent to the shale underlying 

 the limestone mass in the oil wells of western Pennsylvania. The lime- 

 stone is sandy and much of it red. Mr Ashburner discovered a fossilif- 

 erous bed containing Terebratula roiiiingeri, Gramviysia, Strophodonta, 

 Rhynchonella^ while lower down is another from which he obtained a 

 Centronella.\\ This grouping of forms is so w'ell nigh impossible in the 

 upper Mississippian that one must place these identifications in the same 

 list with those which led to recognition of middle Devonian fauna in 

 the Lower Barren Coal Measures of western Pennsylvania. Stevenson 

 found the same t3^pe of limestone on the eastern side in Fulton county, 

 where, however, the limestone appears to be somewhat thicker. On the 

 western side, in Huntingdon county, I. C. White reports 1,050 feet, with 

 the limestone 50 feet broken into alternate bands of limestone and shale 

 and practically non-fossiliferous. In addition to this mass, he discovered 



*H. D. Rogers : Geology of Pennsylvania, 1858, vol. ii, p. 10. 



fJ. P. Lesley: Final report, p. 1823. 



X E. W. Claypole : Prelim, report on paleontolog}' of Perry county (F 2), 1885, p. 79. 



g J. J. Stevenson : Geology of Bedford and Fulton counties (T 2), 1882, p. 68. 



II C. A. Ashburner : Aughwick valley and east Broad Top district, in vol. F, 1878, pp. 194-195. 



