abstracts: geology 455 



ides form, secondary silver minerals are likely to be precipitated as 

 bonanzas near the sm*face, while gold may be carried to greater depths. 

 Abundant pyrrhotite in the primary ore quickly halts the downward 

 migration of both silver and gold. Sidney Paige. 



GEOLOGY. — Kenova, Ky., West Virginia and Ohio, folio. W. C. 

 Phalen. Geologic Atlas of the United States, Folio 184, page 16; 

 with maps and sections, U. S. Geological Survey. 1912. 



The rocks exposed include both the igneous and sedimentary classes. 

 The igneous rocks are peridotite dikes which cover a small area in the 

 western part of the quadrangle and are of interest in having been pros- 

 pected for diamonds. The sedimentary rocks belong in the Carbon- 

 iferous and Quaternary systems. The former system includes both the 

 Mississippian and Pennsylvanian series. Included in the Mississippian 

 are the Logan Formation and the Maxville Limestone. In the Penn- 

 sylvanian are included the Pottsville, Allegheny, Conemaugh and Mo- 

 nongahela formations. Pleistocene and Recent deposits constitute the 

 Quaternary system. 



Tho no part of the quadrangle lies within the glaciated region, it 

 contains deposits of Pleistocene age. These are the low and high level 

 river gravels along the Ohio and Big Sandy Rivers and back of the city 

 of Ashland, in a district known as the ''Flatwoods." They were formed 

 by rivers that abandoned their former courses as a result of the inva- 

 sion of the neighboring region bj'^ ice. 



The asymmetry of the drainage is probably dependent both on pres- 

 ent structure and the character of the rocks which are mainly sand- 

 stones, sandy shales and shales. Excepting the shales, the rocks are 

 water-bearing and produce many springs. The underground currents 

 flow more readily mth the dip than against it, with the consequent 

 tendency for erosion, both surficial and possibly underground to pro- 

 ceed up the dip. Thus the main streams of the region tend to lengthen 

 those tributaries, which, flowing with the dip, erode more rapidly than 

 those flowing against it, and consequently to push the divides between 

 trunk streams westward on the west side of the synclinal axis and east- 

 ward on the east side of this axis. W. C. P. 



