330 
HUBBARD AND CRONEIS 
The Chickamauga formation has the greatest economic value 
of any formation in this system. It has enormous possibilities 
as a cement horizon, can be used for road material or as a building 
stone. In addition to these values, it distintegrates into a very 
rich soil. The other formations of the Ordovician have little 
economic importance. 
The Chickamauga Formation 
This formation takes its name from Chickamauga Creek in 
Walker and Catoosa counties, Georgia, where it outcrops exten- 
sively. The lower layers are usually composed of a chert breccia 
which separates it from the Shenandoah, but where the breccia 
is wanting the separation can be made where the light impure 
limestone of the Shenandoah is replaced by the blue fossiliferous 
beds of the Chickamauga. 
The breccia mentioned above is in some places 50 feet in thick- 
ness and varies from coarse at the base to fine at the top. The 
breccia consists of chert and non-crystalline limestone frag- 
ments in a crystalline limestone matrix. The chert fragments 
are sometimes as large as 15 inches in their greatest dimension 
and are always angular and lie in all positions in the matrix. 
In some localities fragments of sandstone, vein quartz, and 
quartzite occur along with the chert. This breccia seems to 
occur in the same horizon as the Birmingham Breccia of Georgia 
and Alabama, and like that stratum records uplift and erosion 
somewhere not far distant. 
The Chickamauga is usually a blue, flaggy limestone, heavier 
bedded towards the base. It is sometimes separated from the 
lower formation with difficulty; however, the base generally 
carries large quantities of black chert which can be used as a 
distinguishing feature since the upper Shenandoah contains only 
light chert. The formation has a hackly fracture and usually 
weathers blue with water worn rounded forms characteristic. 
This limestone is more jointed and thinner bedded than the aver- 
age Shenandoah. The calcite veining is also more prominent in 
this formation than in the preceding one. The thickness varies 
from 800 feet on East River Mountain to 700 feet on Big Walker 
Mountain. At the Virginian Railroad cut at the Narrows 806 
feet of Chickamauga is exposed. 
The Chickamauga is the great marble producing formation of 
