RUSSELL FORK FAULT OF SOUTHWEST VIRGINIA 365 
fault, reversing the condition of tension which produced the normal 
fault, and producing overthrusting and considerable crumpling 
of the shale and crushing and jointing of the sandstone adjacent 
to the fault plane. The net amount of overthrust is very slight, 
probably at no point reaching 500 feet, and the rocks on the south- 
west side of the fault are nowhere over 250 feet above those on 
the northeast. The shearing loose of the northeast end of the 
block, its overthrust along the already established Pine Mountain 
Fic. 7.—View of Skegg Gap looking north along fault line. At this point the 
resistant basal conglomerate of the Lee on the overridden side (right) is adjacent to 
the weak Pennington rocks of the overthrust side (left). 
fault, and the compression and slight thrusting along the Russell 
Fork cross fault were the closing events in the history of the 
Cumberland block as a unit. 
There are many especial features which are particularly in 
accord with this interpretation of the movement of the Cumber- 
land block as a progressive skew with final release of the east end. 
The skewing of the southwest end of the block first with the Skegg 
Gap corner remaining longest in place explains admirably the 
otherwise anomalous facts of rather strong overthrust in the 
Jacksboro fault, the trace of which is nearly at right angles to 
