PENNSYLVANIAN. 449 



out in the southern quadrangles are mapped as Walden sandstone, the lower portion of which, 

 including the Eockcastle conglomerate member, is accordingly represented in the Lee of the 

 eastern quadrangles, as has just been shown. 



In the McMinnville quadrangle the Walden is reported as 250 feet thick, not thick enough 

 to reach the middle Pottsville; while the Lookout, 200 to 300 feet thick, is here extended to 

 cover the Bonair. Coals are present at the base and just beneath the Bonair ledge. In the 

 Pikeville quadrangle, next eastward, 400 to 650 feet of Walden strata, but slightly surmounting 

 the Rockcastle, remain. These beds include several coals, the most important, near the base, 

 being the Sewanee and Soddy coals. The Lookout, which attains a thickness of 650 feet, has 

 several coals distributed through its section.^^" Walden beds, to a thickness of 500 feet, 

 remain in the Sewanee quadrangle, which reaches nearly to the Alabama line. In this quad- 

 rangle the Lookout expands from 120 feet on the west to 510 feet on the east. The Upper 

 Sewanee conglomerate of Safford, about 250 feet above his Main Sewanee conglomerate, in the 

 Sewanee quadrangle, has been referred by Stevenson to the Rockcastle horizon. 



Even more than in the northern regions the terranes of the Pottsville of the southern Appa- 

 lachian area are highly variable, both in character and in thickness, and are in some places 

 lacking, so that it is difficult to foUow many of the horizons, even when the work is continuous. 

 Thin limestones or calcareous shales are present, especially in the lower Kanawha, and sediments 

 with marine MoUusca are found here and there in each of the major divisions, but none of the 

 marine faunas has yet been foUowed over a great area in the central and southern sections of 

 the coal fields. For these reasons it was found most expedient by the United States Geological 

 Survey in mapping the generally isolated areas of the southern Appalachian region to use for 

 the Pennsylvanian subdivisions local formational names, which were applied to divisions differ- 

 ing as to lithologic characters or, in many cases, arbitrarily segregated for convenience in 

 mapping. The detailed sections of the early publications, which unfortunately are very much 

 scattered and which are generally either deficient in or erroneous as to broader correlations, 

 have been well digested and thoroughly reviewed in a correlative way by Stevenson, who cites 

 nearly all the fragmentary literature." It may be noted that in most of the literature ante- 

 dating the pubhcation of the Federal folios the upper beds of the sections, though of Pottsville 

 age, are frequently referred to horizons as high as the Mahoning sandstone member of the 

 Conemaugh formation or even the Monongahela formation. The data now available are .not 

 sufficient to correlate with accuracy the subdivisions described in the detached areas covered 

 by the folios, but the further study of the paleobotanic material already assembled wiU doubt- 

 less settle many of the points now in question. 



In the Tazewell quadrangle, to the west of the Pocahontas, several of the key rocks of the 

 Raleigh quadrangle are missing. Campbell describes the following formations: 



Tellowa formation, 500 feet (incomplete), sandstones, shales, and coals. 



Sequoyah formation, 450 feet, shales and sandstones with coals. 



Dotson sandstone, 120 feet of sandstone overlying 60 feet of shales. 



Bearwallow formation, 60 feet, conglomerate. 



Dismal formation, 490 feet, shales, coals, and sandstone, including a conglomerate lentil. 



Raleigh sandstone, 100 feet, conglomeratic. 



Welch formation, 700 feet, shales, sandstones, and numerous coals. 



Pocahontas formation, 360 feet, shales, sandstones, and coals, up to coal "No. 3." 



oFor eastern Kentucky see Crandall, A. B., Eastern Kentucky coal field: Geol. Survey Kentucky, vol. C, 1884; 

 Moore, P. M., Geol. Survey Kentucky, newser., vol. 1; Lesley, James, Geol. Survey Kentucky, vol. 4, 1861; Crandall, 

 A. R., Geol. Survey Kentucky, new ser., vol. 6; Hodge, J. M., Preliminary reports on the southeast Kentucky coal 

 field, 1887; Sullivan, G. M., Geology of parts of Jackson and Rockcastle counties, 1891; Loughridge, R. H., Geology of 

 Clmton County, 1890; Norwood, C. J., Ninth Ann. Rept. Inspector of Mines, 1893, and Tenth Rept., 1894. 



For Tennessee see Safford, J. M., Geology of Tennessee, 1869; Bradley, F. H., in Killebrew and Safford, Resources 

 of Tennessee, 1874. 



For Virginia see Rogers, W. B., Geology of the Virginias, and other State reports; Watson, T. L., Mineral resources of 



Virginia; Stevenson, J.J. ,Geologicalreconnaissanceof parts of Lee, Wise, Scott, and Washington counties, Va.: Proc.Am. 



Philos. See, vol. 19, 1881; Hodge, J. M., The Big Stone Gap coal field: Trans. Am. Inst. Min. Eng., 1893; White, I. C, 



Geol. Survey West Virginia, vols. 2 and 2A; and Stone, R. W., Bull. U. S. Geol. Survey No. 316, 1907, pp. 42, 55, 68. 



48011°^— 12 29 



