GEOLOGY OF GILES COUNTY, VIRGINIA 
351 
19. Thin bedded sandstones with little shale partings; sand- 
stones one-fourth to five inches thick. Buff to gray with no red. 
Weathers a uniform buff. Shattered and crackled but there are 
no master joints. Some layers are quartzitic but some are also 
loose sands. Some layers have the appearance of one in un- 
weathered surfaces. Myriads of Cytherellina in the middle. 
13 feet. 
This does not complete the section, as a part of the Rockwood 
is faulted out. On the west side of the river the fault continues 
westward but is some distance farther south so as to leave all the 
Rockwood and a considerable section of Giles north of the fault. 
There may well be, then, 100 feet or more of Rockwood missing. 
THE DEVONIAN SYSTEM 
Introduction 
The outcrops of Devonian strata are confined to restricted 
exposures having a general northeast southwest strike. One of 
these outcrops is on the northern flank of Brushy Mountain, 
another extends into Giles County from Bland on the west, and 
appears for some little distance to the east of the Stange mine 
on Flat Top Mountain. Still other outcrops are found in the 
upper courses of Clendenning, Little Stony, Stony, and Johns 
Creeks, as well as in a small strip across the Panhandle. In the 
south slopes of East River Mountain are considerable areas of 
Giles beds extending from New River almost to the Bland-Giles 
county line. 
There are no good sections of lower Devonian exposed in 
Giles County so that there is some confusion as to the exact age 
of the Giles formation. Some of the rocks which appear above 
the Clinton, and are almost certainly Cayugan in age, are classed 
as Giles, yet the upper Giles bears a marked resemblance faun- 
ally, stratigraphically, and lithologically to the Oriskany. There 
are also occasionally limestones and cherts below this sandstone 
which have been referred to as Helderbergian. 
The Oriskany formation is of importance since it is in this 
horizon that many of the manganese prospects of the county are 
located. The other divisions have no economic value. The en- 
tire Devonian as observed in this area is less than 3000 feet in 
thickness, but it occurs in such scattered outcrops, and in places 
is so faulted that this figure may be either too large or too small. 
