372 
H.UBBARD AND CRONEIS 
The theories for this distribution of strata in separate areas 
will not be developed in this paper any more than to mention that 
Ulrich and Schuchert,^- in their Paleozoic Seas and Barriers, 
have advanced the well founded idea that the area of the Appala- 
chian Valley during Ordovician times was divided longitudinally 
into several narrow troughs, which were rather effectually sep- 
arated, one from the other and that the observed differences in 
sedimentation and faunal life may thus be explained. 
The area covered in this survey lies entirely within a single 
one of these “troughs” but as one ascends the New River and 
comes to the Giles-Pulaski County line, there is noticed at 
once a marked difference in faunal life and lithologic aspect. 
The details cannot be discussed here but it might be interesting 
to note that the Clinch formation in Cap Mountain, is composed 
of three distinct quartzitic ripple making layers, while at the 
Narrows, a scant twelve miles to the west, there are but two of 
these layers and one of these is not distinct. 
The Appalachian series of folds, probably trace their origin 
to pre-Cambrian times. Walcott^'^ demonstrated the existence of 
a long trough, which during Lower Cambrian times extended 
from Alabama northeast to Labrador. This was no doubt what 
we would call a geosyncline and was within the southeastern bor- 
der of a large Algonkian continent. It was during this time, that 
the impure limestones and variegated shales of the Russell forma- 
tion were deposited. At varying intervals, the seas were deep and 
then again they were shallow, until in Middle Cambrian time, the 
Appalachian trough was almost drained of its sea. However, 
long before the close of this epoch, a new period of subsidence 
was inaugurated, and the sea became gradually deeper until in 
Upper Cambrian time it was beyond the Adirondacks and had 
made connection with the Atlantic by way of the restricted 
Appalachian trough. 
For the most part, the Upper Cambrian seas laid down great 
beds of limestone, which are usually dolomitic and non-fossi- 
liferous. These facts seem to indicate that the Shenandoah lime- 
stone, which was laid down at this time, was deposited at a 
considerable distance from the shores and in waters which were 
of a considerable depth. Chemical precipitation will be regarded 
Ulrich, E. O. and Schuchert, Charles, ‘‘Paleozoic Seas and Barriers in 
Eastern North America.” N. Y. State Museum Rept., Bull. 52, pp. 633-664. 
Walcott, C. D., U. S. Geol. Surv. Bull. 81. 
