408 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
limestones, with salt and gypsum beds, here included in the "Green- 
brier limestone." 
The Greenbrier limestone, as that term is here applied, consists of 
the following members, from the top down : 
Feet. 
1. Blue limestone, usually heavy bedded, with some beds of cherty 
limestone, and with occasional beds of grayish, black, or green- 
ish fossiliferous shales near its base 1, 000+ 
2. Shaly limestones, with one or more beds of gypsum, followed 
below by blue shales or slates, which in turn are underlain by 
shales or shaly limestones carrying thick beds of rock salt 600 to 1, 000 
Of the two members the lowermost (2) alone requires attention here. 
While the uppermost member of the Greenbrier limestone appears to 
have a wide distribution, the lower, carrying the salt and gypsum, 
seems to be developed only locally, as it has not been recorded except 
in the region here described. As the salt and gypsum beds are too 
soluble to be well exposed at the surface, and the interbedded shaly 
limestones and shales weather rapidly, it is impossible to find a good 
natural section of this important group of beds. Well sections would 
be of great service, but unfortunately no well has passed completely 
through the series. By utilizing the records of various wells and bor- 
ings, however, some idea of the strati graphy may be obtained. 
At various dates between 1815 and 1857 a number of wells were 
bored on the Robertson property, with the objects of ascertaining the 
thicknesses of the various gypsum beds, and also of determining 
whether or not brine or rock salt could be obtained on the property. 
Through the courtesy of Col. W r . B. Robertson, of the Buena Vista 
Plaster and Mining Company, the writer is enabled to present the 
records of most of these wells. 
The wells started in the gypsum-bearing section of the Greenbrier 
limestone about 200 feet below the massive blue limestones. Several 
of them penetrated through the gypsiferous beds, apparently stopping 
near the top of the salt beds. 
Records of wells on Robertson property. 
Well A, bored between 1815 and 1820: Feet. 
Red clay 0-14 
Clay and plaster 14-120 
Pure plaster « 120-160 
WellB, bored in 1847: 
Red clay 0-10 
Clay and plaster, buhrstones 10-30 
Clay and plaster (deep red) 30-50 
Pure plaster 50-95 
Impure blue plaster . 95-163 
Hard blue slate . 163-420 
"Pure plaster is said to have extended 40 feet deeperthan is above shown— i. e., from 160 to 200 
feet in depth. 
