178 M. R. CAMPBELL — PALEOZOIC OVERLAPS IN VIRGINIA. 



well as southwestward along the valley. Toward the northeast the 

 writer is unacquainted with them, but they apparently hold their own 

 for a long distance in that direction. The distribution of the coal affords 

 a clue to the conformation of the shoreline of the Carboniferous sea, and 

 seems to indicate that here, where the coals are thickest, the coastline 

 could not have been far distant to the southeast. 



Pulaski Shale. — This immediately overlies the preceding formation and 

 is quite conspicuous in the landscape from its brilliant color. Some 

 geologists have inclined to the belief that this series represents the 

 limestone and red shales of the Umbral, but an examination of the rocks 

 in the Cove in Wythe county entirely disproves this idea, for the lime- 

 stones rest directly upon these red shales which are as fully devel- 

 oped there as at Pulaski or on New river ; also this band of red shale 

 can be traced across the valley into West Virginia, where it has dimin- 

 ished in thickness to about 20 feet, but is still persistent. In the same 

 region the Umbral red shales are very prominent in their correct posi- 

 tion above the limestone. There is one exposure that seems to sustain 

 the theory of these shales belonging above the limestone ; this is west of 

 Hamilton knob, where the road south from Max Meadows leaves the 

 hilly country of the Devonian and Carboniferous sandstones and shales. 

 Here the Carboniferous limestone immediately overlies the sandstone, 

 with no red shale between ; but the writer inclines to the belief that there 

 is a slight overlap of the Carboniferous limestones upon the Price sand- 

 stone, and that the red shales were either not deposited here or were 

 eroded previous to the deposition of the limestone. 



STRUCTURE. 



General Features. — The structure of this region is much more compli- 

 cated than the stratigraphy, and has been the cause of the uncertainty 

 respecting the general geology of the region. As has been mentioned 

 before, this area, together with the belt lying along the eastern side of 

 the Appalachian valley throughout its whole extent, has been subject to 

 disturbing influences throughout Paleozoic time. The earlier folds are 

 masked and in part obliterated by the later movements, and the promi- 

 nent structural features of today are those produced by the latest of these 

 periods of activity. The foregoing statement does not agree with the 

 old and popularly accepted idea of the Appalachian revolution, which 

 is that all the folding of Appalachian type occurred in post-Carbonifer- 

 ous time, and that previous to this the entire valley region was under 

 water-level. This old idea is rapidly giving way before the mass of 

 evidence that is accumulating, and which proves conclusively that con- 

 siderable of the folding occurred in Lower Silurian times, and probably 



