144 J. J. STEVENSON CARBONIFEROUS OF APPALACHIAN BASIN 



vania, another in West Virginia and Virginia, and possibly a third in 

 eastern Alabama, though evidence for the last is very indefinite. The 

 lakes were bordered by flats covered with Shenango muds, while farther 

 away on each side were rocks of greater age. That the land on the west 

 side had been exposed for a long period to subaerial erosion is evident 

 from the existence of deep valleys, clearly shown for Kentucky and Ohio 

 in sections by Andrews, Eead, Crandall, Sullivan, and Campbell; for 

 Tennessee and Pennsjdvania by Hayes, D. White, W. G. Piatt, and other 

 observers. The highland of the basin was in New York and western 

 Pennsylvania. 'From the latter the surface declined gently westward into 

 the broad valley of eastern Ohio and eastward to the deep valley now 

 occupied by the Southern Anthracite field. Toward the south the decline 

 was long and gradual, with more rapid descent on the east than on the 

 west side. The great depth of the northern valley basin and the steep- 

 ness of its immediately boimding slope at the west are evident, because, 

 even at the close of the Eockcastle, deposits reached barely into the 

 Northern Anthracite field. The land was trenched by great valleys, hun- 

 dreds of miles long, ending in bays, some of which opened into the 

 Atlantic, others into the interior sea. 



. The northern lake basin containing the Pocahontas, or lowest beds of 

 the Eockcastle, included the Southern and much of the Western Middle 

 anthracite fields. This, first made .evident by Mr David White's studies, 

 is equally evident from the stratigraphical conditions. The southern 

 lake basin may have been somewhat larger than indicated by Mr Wliite, 

 who, out of abundant caution, did not place the boundary beyond that 

 indicated by undoubted evidence in his possession. The stratigraphical 

 evidence seems to justify farther extension southward to very near the 

 Tennessee line, at least for the higher beds. The l^asin thus extended 

 would be about 100 miles long, with an extreme width in southern West 

 Virginia of not more than 60 miles. These small basins, now separated 

 by an interval of 300 miles, may have been united; but if they were, 

 the connecting water strip miist have been very narrow, for even in 

 southern Penns3dvania the Sharon sandstone, the latest Eockcastle de- 

 posit, is the oldest bed in Broad Top of Fulton county. 



The eastern shoreline of the northern basin lay not far from the 

 south side of the Southern Anthracite field and nearer to the eastern 

 than to the western end. Mr David White * has shown that pebbles in 

 the lower third of the Pottsville there are less rounded than those 

 in the upper Pottsville, at times even subangular, while along with 

 the prediminating quartz fragments there are in this lower portion 



* D. White : 20tli Ann. Kept. U. S. Geol. Survey, 1900, p. 764. 



