AO LAL ORs Sie Aes Sahel CAS: Q71 
showing the areal geology, another showing the economic geol- 
ogy, a third of structure sections, and a fourth giving a columnar sec- 
tion north of Clinch River and another south of that river. 
The territory represented by the folio is located principally in 
southwestern Virginia, though the southern portion extends into Ten- 
nessee and the northwestern portion into Kentucky. Its area is 957 
square miles, four-fifths of which is in the Appalachian Valley and 
one-fifth in the Cumberland coal basin. 
The surface features are quite varied. In the Appalachian valley 
they consist of a succession of narrow ridges separated by equally 
narrow valleys, trending in a northeast and southwest direction. In 
the coal basin the ridges are less regular, but higher, reaching in two 
cases an elevation of over 4100 feet above the sea level. 
The region is almost entirely within the drainage basin of the 
Tennessee River. The principal tributaries of this stream are Holston, 
Clinch, and Powell Rivers, each of which is a stream of considerable 
importance. ‘The Kentucky portion of the territory is drained by the 
headwaters of the Cumberland River. 
The geologic structure of the region is complicated. In the 
Appalachian Valley the rocks have been squeezed, in a northwest and 
southeast direction, until they have been forced into great folds. 
These are generally overturned toward the northwest, and have in 
many cases been compressed to such an extent that they have broken, 
allowing one limb of the fold to be thrust over the other. These 
faults are of frequent occurrence in this region. Sixteen or seventeen 
can be counted on the geologic map. In the coal basin the folding 
is less severe, and the result is a broad basin in which dips are prevail- 
ingly light, and in many places the rocks are horizontal. 
The intense folding of the strata has brought to the surface all of 
the geologic formations from the Carboniferous to the Cambrian. On 
lithologic grounds these are divided into twenty-two separate and dis- 
tinct formations. Asa result of the original folding and subsequent 
erosion, these formations show at the surface in long, narrow outcrops 
of limestone, shale, or sandstone, which, in the various folds, are 
repeated over and over again. It is this repetition of the hard beds 
that gives rise to the numerous ridges which are such conspicuous fea- 
tures of Appalachian topography. In the coal basin the rocks are 
nearly horizontal, and hence they show in outcrop around the flanks 
of the mountains, or irregularly over the less rugged portions. 
