152 J. J. STEVEISrSON CARBONIFEROUS OF APPALACHIAN BASIN 



sandstone is very narrow. Coarse material could be pushed only a little 

 way in the shallow water of that time. There is much to suggest a 

 similar advance of the shore at the northwest, not only in the unexpected 

 coarseness of the sandstone, but also in distribution of the limestones. 

 The presence and great predominance of sandstone in Kentuclcy, on the 

 southern and southwestern borders, is equally suggestive of land en- 

 croachment in that direction. 



The Brookville coal bed, the lowest of the Allegheny, underlies in most 

 of the area sandstone or shale, but in Ohio, from Mahoning county on 

 the Pennsylvania border at the north to Hocking and Perry counties at 

 the south, one finds the Putnam Hill limestone, which is sometimes in 

 direct contact with the coal. Throughout this distance the western edge 

 of the limestone lies west from the present outcrop, and south from 

 Perry and Hocking the place of the limestone is west from the present 

 coal area; but conditions in Knox county seem to show that the lime- 

 stone strip was narrow and that it did not extend beyond the valley 

 region in which the Eockcastle and Sharon sandstones occur. Like the 

 Mercer limestones, it carries an abundant marine fauna and marks the 

 line of a sea invasion from the west. One finds on the Kanawha river, 

 in West Virginia, and at the same horizon, the Black Flint, sometimes 

 accompanied by limestone, at times fossiliferous itself and often asso- 

 ciated with fossiliferous shales. . This deposit is confined to a narrow 

 branching area, which may have been near the head of a bay communi- 

 cating directly with the Atlantic. A limestone at this horizon in north- 

 ern West Virginia is non-fossiliferous. 



The Vanport (Ferriferous) limestone marks a still greater inroad of 

 the interior, or Mississippian, sea, reaching in northwest Pennsylvania 

 almost to the New York line. Its easterly and westerly boundaries are 

 distinct in Pennsylvania. At the north and northwest, in Elk, Clarion, 

 Jefferson, and Butler, it passes into chert and cherty sandstone, while 

 on the southeast a prong extends into central Indiana. The deposit is 

 wholly wanting east from the Monongahela and farther north in the 

 First and Second basins of Penns3dvania as well as in West Virginia; 

 but a marine limestone belonging very near this horizon is in Maryland, 

 150 miles southeast from the nearest locality in Pennsylvania where the 

 bed can be recognized. On the Kanawha, in West Virginia, Professor 

 W. B. Eogers* found a bed crowded with marine forms at 140 feet 

 above the Black Flint, too high for the Vanport horizon, but of interest 

 as proving access to the Atlantic at more than one time during the Alle- 

 gheny. During the deposit of the Vanport the water was evidently very 



* W. B. Rogers : Rept. Geol. Survey of Virginia for 1839, p. 135. 



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