GEOLOGY OF GILES COUNTY, VIRGINIA 
321 
the manufacture of cement/' However, the great range in the 
composition of these shales as indicated by the following analysis, 
should lessen the possibilities in this respect. 
ANALYSIS OF THE RUSSELL SHALES 
Vicinity of Clinchport 
(J. H. Gibboney, Analyst) 
1 
2 
Insoluble 
.. 41.72 
89.52 
Alumina and iron oxide 
.. 5.68 
7.22 
Lime 
... 17.32 
0.42 
Calcium carbonate 
.. 30.93 
0.72 
Magnesia 
... 9.17 
1.05 
Magnesium carbonate 
... 19.29 
2.21 
While these analyses were made from samples of the Russell 
formation from a different area than the one under considera- 
tion, they may serve to give spme conception of the composition 
of these shales in Giles County. 
This is the first time that the Russell has been reported from 
Giles County, the reason being that the formation weathers so 
rapidly that it quickly covers itself up. The exposures noted 
above were first found in recent road or railroad cuts. 
CAMBRO-ORDOVICIAN 
The Shenandoah Limestone 
The Shenandoah Limestone is a heavy bedded, gray blue, dolo- 
mitic, limestone near the top, grading downwards into a darker 
more sandy limestone at its base. It takes its name from the 
Shenandoah Valley where it outcrops very extensively. There is 
a breccia at its base in some places whose fragments are made 
up of bits of shales from the older Russell formation. In other 
localities, this formation has been subdivided into or corresponds 
with the Honaker Formation, the Knox Dolomite, and the Noli- 
chucky Shales. It probably corresponds, except for the upper 
portions, with the Beckett Gneiss of New England, the Potsdam 
Sandstone in New York, and the Stissing Slates, all of the Upper 
Cambrian. However, Beekmantown, and even Trenton fossils 
are occasionally found in the uppermost layers. 
This limestone has a thickness of at least 5000 feet at places 
