40 W. M. Fontaine— Vespertine. Strata of Virginia. 



us upon higher and higher strata. This region may then be 

 regarded as an eroded plateau, sloping from the east toward 

 the Ohio Elver. The mountain- 1 i 1 ,],','„ „ ,. , M . t ing in this 

 region are simply uneroded remnants of higher and softer 

 strata, resting upon a basal plane, formed by lower and harder 

 ones, such as the Lower Garb. one, and the 



sandstones of the Conglomerate Series. 



I have attempted to give some account of the topography of 

 this part of the State of West Virginia, in the "Resources of 

 West Virginia," recently published under the direction of the 

 State Board of Centennial managers." 



North of Pocahontas county the flexures along the east 

 border show no fault, but are propagated with diminishing 

 force far to the west. In this quarter the most westerly fauft 

 is the great one, running along the west side of the great Lower 

 Silurian limestone valley of Virginia. The Professors Rogers, 

 in their (lis ,, :ture f tne Appalachian Belt in 



the Virginias, have well shown the gradation of folds, in the 

 northern part of the area in question," into faults in the south- 

 ern part. In passing south the anticlinals become closed, then 

 overturned to the west, and finally fractured. This feature is 

 shown, as I have explained above, in the Devonian area near 

 the White Sulphur. 



An inspection of the map of the Virginias will show that the 

 straight mountain chains which extend from the southern part 

 of the two states in a northeasterly direction to the northeastern 

 corner of Monroe county, are then thrown farther west, and 

 made to take rly direction. The more south- 



erly chains are produced by resistant strata, brought up along 

 lines of fault, the more northerly, by folds. 



The following seems to me to be the course of events, which 

 resulted in the production of the of the coun- 



try : 



The westward thrust, which, at the close of the Carbonifer- 

 ous Age, uplifted the Appalachian Belt, found the strata almi" 

 its present western border, for some distance- south of the 

 .Potomac, with their power of resistance comparatively unim- 

 paired by any previously existing tension. Consequently, the 

 undulations arising from the thrust were propagated far to the 

 west But to the south the case wasdifferenf. The western ed-e 

 was already weakened by the tension nrodueed by the develop- 

 ment of the deep trough, in which the lower Carboniferous strata 

 were deposited, and tins tension increased with tin; increased 

 depth of this trough to the south. Hence, we find first the 

 development of a minor fault along the eastern side of Green- 

 brier county, which relieved the strata to the west of it in a 

 great measure, from the westward thrust. 



