eckel.] SALT AND GYPSUM OF SOUTHWESTERN VIRGINIA. 407 
STRATIGRAPHY AND STRUCTURE. 
The areal geology and structure of the district have been carefully 
worked out by Professor Stevenson, and are described by him in the 
paper cited below. a 
In the forthcoming bulletin on the gypsum deposits of the United 
States, to be published soon by this Survey, will be found a geologic 
map of the Virginia salt and gypsum region, with structure sections, 
modified very slightly from that published by Professor Stevenson. 
A summary of the more important geologic features will here be given. 
The ridges (Brushy Mountain, Pine Mountain, Little Brushy Moun- 
tain, etc.) which border the valley of the North Fork of Holston on 
the northwest are made up of Upper Silurian, Devonian, and Lower 
Carboniferous rocks, dipping southeastward (or riverward) at angles 
of 20° to 40°, and striking approximately parallel with the course of 
the river. The southeastern slope of these ridges is generally formed 
by the shales and shaly sandstones of the Lower Carboniferous which 
underlie the Greenbrier limestone. The Greenbrier limestone itself 
occupies the interval between the foot of the ridges and the river, and 
extends, on the southeastern side of the river, to the great fault 
described as the Saltville fault by Stevenson, and farther south as the 
Rome fault by Hayes. This fault brings up Cambro-Silurian lime- 
stones on its southeastern side. The location of the fault in the salt 
and gypsum district may be described as follows : Beginning at the 
southwestern end of the area, the fault crosses the Saltville branch rail- 
road at a point several hundred yards south of the plaster mill of the 
Buena Vista Plaster Company, runs a little above the foot of the ridges 
on the southeast side of the salt wells, and in a direction approximately 
north, 60° east, crossing the river near Broad Ford, and passing north 
of the settlement at Chatham Hill. The rocks on the southeastern 
side of this fault are limestones and shales of Cambrian and Lower 
Silurian age, dipping southeastward, and ma}' be disregarded in a 
further discussion of the salt and gypsum deposits. Trilobite remains 
occur in these Cambro-Silurian limestones in a railroad cut south of 
the Buena Vista mill. 
SALT AND GYPSUM DEPOSITS. 
In describing the geologic and areal relations of the salt and gyp- 
sum deposits, the area southeast of the Saltville fault may, as above 
noted, be dismissed from consideration. The deposits are confined to 
a belt north of this fault, and extending from the fault line to the 
line of outcrop of the Lower Carboniferous standstones, which passes 
along the foot of Pine Mountain and Little Brushy Mountain. This 
intervening space is occupied by the massive limestones and slial} 7 
n Stevenson, J. J., Notes on the geological structure of Tazewell, Russell, Wise, Smyth, and 
Washington counties of Virginia: Proc. Am. Philos. Soc, Vol. XXII, pp. 1 14— lt>l . 
