352 CHESTER K. WENTWORTH 
by Hinds being but part of a continuous fault or zone of faulting 
from the Hunter Valley fault at Big A Mountain to Skegg Gap in 
Pine Mountain, and the author was requested to examine the 
region as carefully as the limited time at his disposal would permit, 
in order to establish the character and extent of the movements 
that produced the disturbance. ‘The result of his examination was 
the establishment of the presence of an overthrust fault entirely 
across the great crustal block, thus showing that it is bounded on 
all four sides by overthrust faults and that it has moved bodily 
to the northwest a distance of many miles. The results of his 
studies and their application to the mechanics of the problem of 
the overthrusting of this great mass of strata for at least six miles 
are here set forth. 
The fault bounding the crustal block on the northeast, which, 
on account of its general agreement with the course of Russell Fork, 
is here called the Russell Fork fault, was mapped in connection 
with coal investigations carried on co-operatively by the Virginia 
Geological Survey and the federal Geological Survey. The areas 
mapped as undifferentiated buckled and faulted rocks by Hinds,* 
on the Clintwood and Bucu quadrangles, were subjected to careful 
study by the writer to determine whether or not there was a | 
continuous break across the coal-measures trough from the vicinity 
of Big A Mountain to Skegg Gap, but in the two weeks spent 
on this study there was not time to cover much of the area lying 
on either side of this zone and the structure contour maps of the 
report by Hinds furnished many data in compiling the sections 
shown below and in deducing the amount of displacement. 
The writer is indebted to Mr. M. R. Campbell for many helpful 
suggestions and much assistance in the course of the study. 
Hinds, in his report on the coal resources of the Clintwood 
- and Bucu quadrangles, describes the structure of the northeastern 
end of the Middlesboro syncline in considerable detail. His studies 
here and farther northeast in Buchanan County? have shown that 
Op. cil. 
2Op. cit. 
.3 Henry Hinds, “‘Geology and Coal Resources of Buchanan County, Virginia,” 
Virginia Geol. Survey Bull. r8 (1918). 
