1887.] ^^ [Stevenson. 



A Oeological Reconnaissance of Bland, Giles, Wythe and portions of 

 Pulaski and Montgomery 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, March IS, 1887.) 



Introduction. 

 I. The Faults and Folds. 

 II. The Groups, xoith comparative notes. 



III. The Area north from Walker mountain, Bland and Giles counties. 



IV. The Area south from Walker mountain, Wythe, Pulaski and Mont- 



gomery counties. 



INTRODUCTION. • 



The reg'ioa described in this memoir, embracing Bland, Giles, Wythe 

 and portions of Pulaski and Montgomery counties of Virginia, is the east- 

 ward continuation of the region described in the writer's previous mem- 

 oirs* on the geology of Southwestern Virginia. 



The examination of the area under consideration was purely a recon- 

 naissance, and the notes in several localities must be regarded as little 

 more than suggestions to the one who may make the detailed study on 

 behalf of the United States Geological Survey. 



The whole area is rugged. Even the Great valley, so wide in Washington 

 and much of Smyth county, becomes broken in Wythe by the introduction 

 of Potsdam ridges south from the railroad, while a new fault originating in 

 Wythe county reproduces Big and Little Walker mountains in Cove and 

 Max Meadows mountains north from the railroad. These break the val- 

 ley in Pulaski county also, while the fiiults of Price mountain hold be- 

 tween them a Carboniferous area, which divides the valley in Montgom- 

 ery county from New river almost to 'the line of Roanoke county. The 

 whole region from the Tennessee line north-eastward to beyond the New 

 river, as far as the writer has gone, is broken by successive pairs of Silu- 

 rian and Devonian mountains separated by valleys of Lower Silurian 

 limestone. 



The Walker mountains. Big and Little, originating in Smyth county, 

 are continuous to beyond the eastern border of Montgomery county. The 

 latter ridge changes its name twice, becoming Cloyd's mountain as it ap- 

 proaches New river and Brush mountain beyond that stream ; while the 

 former retains its name to the river and thence becomes Gap mountain. 

 Big Walker maintains its rugged features throughout and shows but two 

 water-gaps, those made by Walker's creek and New river, which are sep- 

 arated by barely seven miles. Some wind-gaps exist, one of which, near 



* These were read before this Society and are to be found in the Proceedings, Vol. xix, 

 pp. 88 to 107, 219 to 262, 498 to 506 ; and Vol. xxii, pp. 114 to 161. 



