6S J. J. STEVENSON — LOWER CARBONIFEROUS, APPALACHIAN BASIN 



from Pulaski, but they have suffered so severely from erosion that the 

 writer made no effort to estimate their thickness. The silicious lime- 

 stone is there, but very thin, less than five feet. 



The Brush-Cloyd-Little Walker Mountain strip, forming the northerly 

 boundary of Montgomery, Pulaski, and Wythe counties and extending 

 a little way over into Smyth county, shows no limestone in Montgomery, 

 according to Fontaine and Stevenson. The latter found no limestone in 

 Pulaski county, and onl}^ the silicious limestone 7 or 8 feet thick in 

 western AVythe. The thickness of the shales in New River gap, through 

 Little Walker mountain, was estimated at 996 feet, the boundary be- 

 tween Mauch Chunk and Pocono being drawn arbitrarily, there being 

 no limestone present; but the limit as given accords with the place of 

 the silicious limestone in Wythe and Bland. The silicious limestone, 

 still very thin, was seen in southern Bland county, north from Wythe, 

 along the foot of Brushy mountain, where also a streak of coal occurs in 

 the overlying shales. The shoreward boundar}^ of the silicious lime- 

 stone extended along the strike within the valley little farther than 

 the eastern border of AVythe county. It ma}^ have reached as far as the 

 line of the Blue Ridge, for the fragment on the Norfolk and Western rail- 

 road is within 12 miles of the pre-Cambrian rocks. The limestone mass, 

 so thick at only a few miles west and northwest, appears to be repre- 

 sented in Wythe and Bland only by a few feet of the silicious limestone 

 and to be wholly wanting in Pulaski and Montgomery.* 



The fault of Walker mountain diminishes westwardly, so that its Mis- 

 sissii)pian area is cut off suddenly at a little way beyond the Smyth 

 Count3^1ine; but the great Saltville fault increases in that direction, 

 and its Brushy Mountain exposures continue through Smyth and Wash- 

 ington counties into Tennessee. Along this line the limestone increases 

 in thickness, so that in central Smyth county it becomes a notable fea- 

 ture, attaining its greatest thickness in Washington where the Holston 

 river breaks through Brushy mountain. There Stevenson estimated the 

 shales at 1.000 feet, the upper limestone at 1,270 feet, and the lower at 

 755 feet. These were merely estimates made during a preliminary recon- 

 naissance, and they are doubtless excessive. The shales consist of red 

 shales, fine grained sandstones, and grits, with some thin limestones, the 



'*J. J. Stevenson: Proc. Amer. Phil. Soc, vol. xxiv, pp. 75, 76, 100. Mr M. R. Campbell visited 

 this region several years after the publication of results obtained bj' Fontaine and Stevenson. 

 He came to very different conclusions respecting the relations of the Price Mountain shales, as 

 well as of those along Little Walker mountain. He does not regard them as contemporaneous 

 with the Greenbrier limestone, as he recognizes that limestone in Wythe county, where lie finds 

 a thickness of about 1,500 feet, as opposed to the practical absence of limestone asserted by Ste- 

 venson. It is impossible to reconcile these figures, and nothing can be done now further than to 

 state the case. For the present, however, the writer prefers to accept his own observations as 

 apparently in accord with conditions in similar petty areas fartlier south. 



