266 JS. SJ. Stevenson—Fauilts of Southwest Virginia. 
Mountain fault; so that in the very heart of the “ Great Val- 
ley ” there is a block of Upper Silurian, Devonian and Lower 
Carboniferous with Lower Silurian on two sides, Cambrian on 
the third and Lower Carboniferous on the fourth. 
A curious double fault, that of Price Mountain in Mont- 
gomery County, brings up a short anticlinal ridge of Lower 
Carboniferous midway in the valley. This V-shaped fault is 
short and its branches are separated by an interval of not more 
than three miles and a half at the widest place. 
The faults do not follow straight lines and their courses 
show much variation. The intervals show equal variation. 
As has been said already the vertical extent of a fault is not 
the same along the whole line. It was observed that the faults 
where followed out proved to be merely cracked anticlinals; 
the most notable illustration being found in the Copper Creek 
fault, which disappears in the Elk Garden anticlinal, only to 
reappear after a distance of seventy miles in the Winonah and 
Buckhorn faults, which in their turn disappear in an anticlinal. 
The Max Meadows, Draper Mountain, Abb’s Valley faults and 
the three small faults of Lee and Scott Counties illustrate the 
matter almost equally well. Such being the origin of the 
fault, variation in the vertical extent must be looked for. 
But the strength of the throw may be the same for a long 
distance while the apparent strength may be very different. 
The development of anticlinals on one side or the ‘other, anti- 
clinals belonging to a time prior to the formation of the faults, 
may cause the appearance of successive groups on one side. 
An admirable illustration is found in the Saltville fault, which 
has Knox limestone on the upthrow side throughout the whole 
distance examined, while on the downthrow side one finds the 
whole series from the Knox limestone to the Umbral shales, 
possibly to the Coal-measures. But the extent of the throw is 
the same throughout, the variation being due to the presence 
of anticlinals crossed by the fault. 
The Hunter Valley fault or Clinch uplift illustrates well the 
variation in strength of the throw. Where it enters from 
Tennessee it shows Knox on the tpthrow and Clinton on the 
downthrow side; but within a few miles Hamilton is on the 
downthrow, while within ten miles farther, Lower Coal-meas- 
ures (Quinnimont) are in the fault on the downthrow side. 
The upthrow diminishes in Russell County beyond the origin 
of the New Garden fault so that Middle Coal-measures are in 
contact first with Devonian and then with Lower Coal-measures. 
The Walker Mountain fault illustrates the same thing equally 
well, for though it enters as a fault in the Knox the down- 
throw oradually i increases until in Wythe County the whole 
series to the top of the Umbral is seen. 
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