-Vespertine Strata of Virgin 



(Concluded from page 48.) 

 Vespertine of Augusta and Rockingham Counties. 



My principal examinations in this quarter were made at 

 "North River Gap," in the northern corner of Augusta county, 

 in the " Dora Coal Field." In this part of the State the eastern 

 edge of a fractured portion of the Vespertine area seems to 

 have been pressed down against the massive Lower Silurian 

 limestone, along the line of fault which runs on the west side 

 of the "Valley of Virginia." This has resulted in the overturn 

 of the strata westward, and the catching of a narrow synclinal 

 belt of the middle member under the massive sandstones of 

 the lower portion. These, by their resistance to erosion, have 

 preserved from removal the more destructible strata of the coal- 

 bearina forks, an 1 - n.linu up in huge ribs, form the core of 

 the Great Xmt Mount in here. .11 •! locally, "Narrow Back." 

 As might be expected, especially in the mountain itself, the 

 amount of contortion ami crushing is immense. 



The sandstones are changed to quartzites, with all granular 

 structure obliterated. The shales which contain the coal, from 

 their more yielding nature, have suffered most. Where they 

 are exhibited in the western face of the mountain, they are 

 thrust through the coal seams, and wrapped in the most com- 

 plicated coo -•> have been drenched 

 with water I a contain 

 lumps and strums of quartz, deposited by such waters. Yet 

 with all this, thev are true shales, being rendered only more 

 C' n pn t ind hard'ci This is moth i si m. > \ miple of the 

 difference in the amount of metamor > lie action, produced in 

 sandstones and shales, when subjected to the same influences, 

 and of the insufficiency of mechanical disturbance to produce 

 more than the ; ; mrpliism. 



The convoluted and disturbed strata of the mountain dip 

 southeast at a high angle. After passing it to the weal 

 flattens rapidly, and while the rocks of the mountain are in- 

 verted, we now find them in tin u '-'.""">' 

 compare ti sit to a risli-hook, with its shank 

 turned westward, the bend representing the mountain. The 

 material of the hook would re ■ t ' 3 ot * he 

 lower Vespertine, while we may lle member 

 with its coals as filling the curve, and resting upon t 

 It will thus be seen that the number of coal beds will be 

 doubled by overlap in the west face of the mountain. Ihe 



