Stevenson.] 



222 



[Jan. 21, 



of Kentucky and Virginia, maintains that Stone mountain is not a fault, 

 but that it is a sharp fold and a typical example of the Cumberland moun- 

 tain structure. The exposures beyond Little Stone gap and at Penning- 

 ton's gap show this to be true. It is precisely like the structure of Brush 

 mountain, Kentucky, of which an illustration is given in a long cross-sec- 

 tion accompanying another of Mr. Moore's reports. At Pennington's gap 

 the succession of Upper Silurian, Devonian and Lower Carboniferous is 

 clear, and all the groups are conformable. Figures 1, 2 and 3 exhibit the 

 structure of the whole fold ; No. 1 being a cross section from the northerly 

 slope of Stone motmtain to Powell mountain ; No. 2, a similar section 

 through Big Stone gap, and No. 3, the section from Pennington's gap to 

 Wallen's ridge. 



Fig 1. — Section from Stone mountain at Little Stone gap to Powell mountain. 

 a. Slope of Blaclc mountain; b. Stone mountain; c, Powell mountain; 1, Coal 

 Measures; 2, Quinnimont group; 3, Lower Carboniferous; 4, Devonian; 5, 

 Upper Silurian ; 6, Lower Silurian. 



Fio. 2.— Section from Stone mountain at Big Stone gap to Powell mountain. 

 a. Slope of Black mountain; 6, Stone mountain; c, Poor Valley ridge; d, 

 Wallen's ridge ; e, Powell mountain ; /, fault of Poor Valley ridge. Numbers as 

 in preceding figure. 



Fig. 3. —Section from Stone mountain at Pennington's gap to "Wallen's ridge, 

 a, Slope of Black mountain; 6, Stone mountain; c, Poor Valley ridge; d. Chest- 

 nut ridge; e, ElkKnob; h. Wallen's ridge ; /, fault of Poor Valley ridge. Num- 

 bers as in preceding figures. 



The change of structure beyond the fault of Poor Valley ridge will be 

 explained in its own place. 



Wallen's ridge includes the eastern extremity of Poor Valley ridge, 

 and the two ridges become separate only beyond the mouth of South Fork 

 of Powell river. Lower Silurian rocks are shown on its northerly side, 

 Medina sandstone forms the crest, while Lower Helderberg and Oriskany 

 are shown on the southerly slope. The structure, where the ridge first 

 separates itself from Poor Valley ridge, is shown in Fig. 2, which repre- 

 sents the cross-section from Poor Valley ridge fault across Turkey Cove, 



