GEOGRAPHICAL CHANGES DURING PENNSYLVANIAN 151 



and at present there is little ground for supposing that it ever reached 

 much farther south than northern Tennessee. 



The sandstones of the Allegheny contrast greatly with those of the 

 Eockeastle, even vs^ith those of the Beaver. They are persistent only as 

 narrow bands, and in any given area are apt to be replaced for con- 

 siderable distances by sandy or even by clayey shale. Along the eastern 

 outcrop from Kentucky northeastwardly into Eandolph and Upshur 

 counties of West Virginia the sandstones are very conspicuous, very 

 coarse, and at times for miles almost continuous from bottom to top of 

 the formation, composing in part Mr Campbell's Charleston sandstone. 

 Farther north, in the Potomac area, the sandstones are differentiated, 

 broken by beds of shale; yet even there the Butler and Clarion are 

 massive, the former at times pebbly. The sandstones are irregular in 

 Broad Top and the pebbles are few. Within western Pennsylvania the 

 Butler and Freeport sandstones appear to be most nearly persistent and 

 each of them occasionally shows some pebbles; but they vary greatly in 

 thickness and each of them is often replaced by shale in tracts containing 

 hundreds of square miles. Well records in the deep portion of Ohio 

 and West Virginia usually show more or less of sandstone in one or 

 more of the intervals, but many show so little aside from shale that the 

 sandstone must be due merely to local sorting of material. Pebbles are 

 reported only from Wirt county of West Virginia. The great sandstones 

 of the eastern outcrop in West Virginia break within a few miles toward 

 the northwest; thin shales appear, which soon increase in thickness, and 

 the sandstones become unimportant. Along the western outcrop in Ohio, 

 sandstone is most nearly persistent in the Butler and Freeport intervals. 

 Ordinarily fine in grain, the latter shows pebbly streaks in Stark, Carroll, 

 Harrison, Wayne, Tuscarawas, and Muskingum counties — that is, along 

 the northwestern side ; yet in all of these counties not a few sections show 

 only shale. The Clarion (Hecla) sandstone becomes very conspicuous 

 in southern Ohio and is equally so farther south and southwest in Ken- 

 tucky. It is noteworthy that a conglomerate is present in parts of Ken- 

 tucky near the horizon of the Vanport limestone, and that at one locality 

 the ore associated with that limestone is so crowded with quartz pebbles 

 as to be worthless. 



The character and distribution of the sandstones show sufficiently a 

 great advance of the shoreline or a considerable elevation of land at the 

 southwest. The former condition seems the more probable, and the 

 Allegheny deposits can have extended hardly so far in that direction as 

 did those of the Beaver. The shoreline at the east-southeast must have 

 been at only a short distance from the present outcrop, as the strip of 



