eckel.] ARKANSAS. 95 
limestone overlying the chert; and (3) the limestone in the chert bed. 
[The bed underlying the chert has been designated the St. Joe limestone 
and has been described in detail on the preceding pages (93-94). 
LIMESTONE OVERLYING THE CHERT BED. 
Description. — The limestone overlying the chert bed is classed as 
[part of the chert bed, but in many places it is apparently a separate 
|bed. In most places it is " dark gray on a fresh fracture, but on 
■exposure the color changes to a light gray on account of the loss of 
Bituminous matter. In some places the rock is almost entirely free 
from organic matter. It is coarsely crystalline, slightly fossiliferous, 
||homogeneous in texture, and very tenacious; has a conchoidal frac- 
jture, gives out a fetid odor on a fresh surface, and rarely presents 
Ipharp edges on weathered exposures, but outcrops in rounded bowl- 
Biers or prominences through the soil. In places the limestone con- 
Itains numerous small fragments of angular chert. 
Distribution. — The limestone overlying the chert bed was not 
■observed in the eastern part of northwestern Arkansas where, however, 
limestone does occur in many places near the top of the chert bed, but 
either contains intercalated chert or is overlain by thin layers of chert, 
mnd is distinct lithologically from the bed overlying the chert in the 
Ivestern part of the area. a It occurs in the western part of the State, 
In Carroll, Madison, Benton, and Washington counties, where it out- 
Iprops around the numerous outliers of the Boston Mountains. Com- 
Ibaratively small quantities of it are exposed on Grindstone and Pond 
inountains, near Eureka Springs, but on Swain Mountain, T. 19 N., 
fe. 26 W., it forms a prominent ledge around the east end of the 
[mountain between the chert and the overlying Batesville sandstone, 
butcropping in rounded ledges along the Eureka Springs -Hunts vi lie 
|*oad, where it is very dark, almost black, on a fresh surface. It is 
Ifexposed in large quantities in Stanley Branch around the borders of 
fthe Batesville sandstone areas, in heavy ledges around the base 
jpf Keefer Mountain south of Hindsville, about Goshen, in T. 17 N., 
Ik. 28 W., on the tributaries of Richland Creek, and on Poor, Ellis, 
Iumphrey, Blansett, and other mountains on the west side of White 
iver. 
LIMESTONES IN THE BOONE CHERT. 
Description. — Though most variable in quantity and quality, the 
iimestones in the Boone chert form some of the largest and most val- 
able beds in North Arkansas. Instead of a persistent, clearly defined 
>ed of limestone running through the chert, there is rather a bed of 
hert, with large quantities of limestone variously mixed through it. 
n some places the limestone occurs in irregular layers, varying from 
a Mr. E. O. Ulrieh states that part <>f this limestone— the black variety— is a bed in the basal part of 
le Fayetteville shale. 
