ABSTRACTS 415 



presents a confused mass of irregular ridges and hills, only the sum- 

 mits of which reach the original level of the plateau. 



The geologic structure of this region varies as the topography 

 varies. In the northern portion the rocks are nearly horizontal, their 

 northwestward slope being rarely more than 200 feet per mile, whereas 

 in the southern portion the rocks have been highly compressed in a 

 horizontal direction, forming huge folds, which in many places have 

 broken, allowing one portion of the fold to slip over the other. It is 

 this tilted condition of the strata which gives rise to the regular topo- 

 graphic forms of the Appalachian valley. The attitude of the rocks is 

 shown on the structure-section sheet by four sections which cross 

 various portions of the territory. 



The geologic history of this region is recorded in the rocks, which 

 tell of prevailingly marine conditions from early Cambrian to late 

 Carboniferous time. There were deposited during that time sediments 

 to the extent of 17,000 or 18,000 feet in thickness, which have since 

 been hardened into limestone, shale, and sandstone. Of this great 

 mas-s the limestones form about 6700 feet; the shales 9500 feet; and 

 thfe sandstones, about 1400 feet. On lithologic grounds these have 

 been divided into twenty -three separate and distinct formations, 

 which are shown on the general geologic map by various colors and 

 patterns. 



There is little variety in the mineral resources of this region. Coal, 

 iron ore, and marble constitute about all of the mineral wealth of the 

 territory. A limited area of coarse gray marble occurs along the 

 northern front of Big Walker Mountain, but no development has been 

 undertaken. 



Iron ore occurs in two formations of the Upper Silurian rocks. It 

 is of good quality, and probably in sufficient quantity to be of com- 

 mercial importance, but its inaccessibility has prevented develop- 

 ment. 



Coal is by far the most important mineral resource of this region. 

 The territory represented by this sheet embraces almost the entire Flat 

 Top or Pocahontas coal field at present developed. All operations are 

 confined to the great No. Ill or Pocahontas seam of coal, which is 

 semi-bituminous and ranges in thickness from four to ten feet. It is 

 exposed along the valley of Bluestone River from Pocahontas to the 

 edge of the territory ; along Tug Fork ; in the valley of Elkhorn Creek 

 from Coaldale to Kimball, near the edge of the area; and at several 



