Stevenson.] ii'l [Nov. 21, 



Notex on tJie Geological Structure of Tazewell, Rusxell, Wise, Smyth and 

 WasJdngion Counties of Virginia. By John J. Stevenson, Professor of 

 Geology in the University of the City of New York. 



{Read before the American Philosophical Society, November 21, I8S4.) 



Introduction. 



I. Geological Structure : the Faults and AnticUnals. 



II. The Several Groups. 



III. The Area drained by Holston River. 



IV. The Area drained by Clinch River. 



V. The Salt and Gypsum Deposit of the Holston Valley. 



INTRODUCTION. 



This memoir is practically a continuation of the writer's memoirs on 

 southwestern Virginia, read before this Society in August, 1880, and in 

 January, 1881. In it the description is carried eastward so as to connect 

 witli the reconnaissance work described in the writer's memoir, read in 

 October, 1881. Tliis, however, differs from those in that it contains no 

 references to economic geology except in so far as may be needful to the 

 explanation of structure. 



Little has been published respecting the geology of this region, the only 

 memoir of material importance being that by Prof J. P. Lesley, read be- 

 fore this Society in 1871.* The writer is indebted to this for some useful 

 information, which will be acknowledged fullj' in its proper place. A 

 note in Science by Mr. E. G. Squier, makes one wish that that observer 

 had publislied more of his work. Brief notices of the Saltville basin and 

 vicinity have been published by Profs. W. M. Fontaine and C. H. Hitch- 

 cock, but these give little of detail. 



Like the region described in the writer's previous memoirs, this shows 

 no monotony of surface. The Great valley of Virginia, with its floor of 

 Cambro Silurian rocks, occupies a great part of Washington and Smyth 

 counties, and has as its north westerly boundary the irregular Walker 

 mountain. That mountain is a low ridge of limestone in Washington 

 county, but in Smj^th county it becomes double, consisting of a Medina 

 ridge. Big Waliter, separated by a Clinton valley from the Devonian 

 ridge. Little Walker, which overlooks the valley. Rich valley separates 

 Big Walker mountain from Brushy mountain, a ridge of Devonian and 

 Lower Carboniferous, which is separated by a narrow and somewhat in- 

 definite Poor valley from Clinch mountain, these two ridges bearing the 

 same relation as Big and Little Walker. There is then a succession of 

 "Poor" and "Rich" valleys; the latter, with limestone soils, are either 



♦Lesley. The Geological Structure of Tazewell, Russell and Wise Counties 

 In Virginia. Read April 21, 187]. 



