GEOLOGY OF GILES COUNTY, VIRGINIA 371 
Soils 
For the most part in this area, the soils and the rocks from 
which they are derived, are equally differentiated, so that the 
areal map may be followed with considerable accuracy. The 
sandy soils derived from formations such as the Bays and the 
Clinch are of no importance for agricultural purposes. For the 
most part, shale does not disintegrate into a fertile soil; how- 
ever, the Sevier shale contains enough calcareous material to 
make it quite productive. This formation, however, usually out- 
crops so high and on such steep slopes that it ordinarily cannot 
be used. The Chickamauga ranks the highest as a soil producer 
and is responsible for the rich farming lands of the Pearisburg 
area. The Shenandoah limestone also disintegrates into a fairly 
fertile soil but it also leaves behind it a mantle of the insoluble 
chert which makes cultivation difficult, but not impossible. 
No doubt the soils of the county constitute, at present, the 
most valuable geologic resource available. 
RESUME OF GEOLOGIC HISTORY 
As has been mentioned in the introduction, the area under dis- 
cussion lies in that division of the Appalachian Highlands, 
known as the Appalachian Valley Province. Giles County is sit- 
uated at the extreme southern end of the Middle Section of this 
province. In northwestern and in the central western portions 
of Virginia, there is no great difference in the stratigraphic suc- 
cession or in the lithology of the Ordovician and Silurian strata. 
In the area comprising most of southwestern Virginia, however, 
a new factor is introduced in the study of these same rocks. 
Ordinarily, rocks deposited synchronously in comparatively small 
areas exhibit no great differences either in fossil fauna or in 
lithologic aspect. In the division of the state mentioned above, 
the rocks differ in different areas, in both of these respects. In 
the eastern portion of the great valley, the development of the 
Ordovician strata is entirely different from that found in the 
westernmost portions of the state. In studying the various sec- 
tions, these discrepancies in apparently the same age of strata 
are encountered in traverses made across the valley rather than 
in directions paralleling the length of the valley. 
Physiographic Divisions of U. S. Ann. Assoc. Amer. Geog. Vol. VI., 
pp. 19-98. 
