14 THE CLAYS OF ARKANSAS. 
CARBONIFEROUS SYSTEM. 
MISSISSIPPIAN SERIES. 
Several divisions of the Mississippian rocks have been recognized 
in Arkansas. Brief mention is made of each of these owing to the 
important bearing which the limestones and shales have on the pro- 
duction of clays and, consequently, the necessity for guidance in 
identifying the formations and in determining their areal distribution. 
Boone formation. — The Boone formation consists in the main of 
a series of cherty limestones and cherts that has been known as the 
" Boone chert," a name given to the series on account of its wide 
distribution in Boone County. Below these over a large area in the 
northern part of the State lies the St. Joe limestone member of the 
formation, a well-marked bed of gray or pink crystalline limestone, 
which is the basal Carboniferous bed. It is easily recognized by its 
color, texture, and its marked contrast with the beds that usually 
underlie it. This limestone forms an almost unbroken outcrop from 
the vicinity of Mountain View, in Stone County, to the State line 
near Seligman, Mo. Where the cherts contain much limestone they 
form, on decay, a very fertile soil. The fine farms of Boone County 
about Harrison, Valley Springs, Belfonte, and Rally Hill are on the 
" Boone chert." This formation covers the greater part of Benton 
County and the northern and western parts of Washington County. 
Where the chert is comparatively free from limestone beds the soil 
is too meager for agriculture and forms the " flint hills" of western 
Carroll and northern Madison counties and the watersheds north of 
Marshall and southwest of Rush Creek, in Marion County, and the 
hilltops about Elixir Springs, Boone County, and Doddsville, Marion 
County. 
Moorefield shale. — In the vicinity of Bates ville there is a bed of 
shale lying on the Boone formation. It is well exposed around 
Moorefield, from which place it is named. In that locality it has a 
thickness of from 50 to 75 feet. To the west, at Marshall, it is not 
over 35 feet thick, and evidently it does not extend much farther 
westward. The shale has a light grayish or bluish color and is very 
friable. In places it is sandy. It is not important, but is described 
here in order to give the full sequence of rocks in the section along 
the northern border of the Boston Mountains. 
Batesville sandstone. — Next above the Moorefield shale is the Bates- 
ville sandstone, so named from the town of Batesville, which is built 
on this sandstone. It is present along the base of the slopes of the 
isolated hills and mountains north of the Boston escarpment, in 
Independence, Stone, Searcy, Newton, Boone, Carroll, Madison, 
Washington, and Benton counties. The rock is coarse, cream-colored 
to brown, often false bedded, and in some places contains beds of 
