THE CLAYS OF ARKANSAS. 
By John C. Branner. 
CHAPTER I. 
TOPOGRAPHY AND GEOLOGY. 
GENERAL FEATURES. 
The broader topographic and geologic features of Arkansas are 
not local and characteristic but are rather portions of several physio- 
graphic divisions which find completed expression in areas beyond 
the borders of the State. Nearly all that part of the State lying 
northwest of a line drawn diagonally across it from northeast to 
southwest (from Randolph County to Little River County) is com- 
paratively elevated, and is divided by the Arkansas River valley 
into the Ozark JPlateau (including the Boston Mountains) on the 
north and the Ouachita Mountain region on the south. This north- 
western portion is underlain by limestones, sandstones, and shales, 
which are approximately horizontal in the Ozark region, broadly 
folded in the Arkansas Valley, and highly folded and distorted in the 
Ouachita Mountains. 
The Ozark Plateau region north of the Boston Mountains is deeply 
dissected by stream erosion. Its topography is therefore rugged, 
but the local elevations rise to the same general level. In the Bos- 
ton Mountain region, which overlooks the plateau from an irregular 
northward-facing escarpment 500 to 700 feet above it, the topog- 
raphy is largely of the terrace and escarpment type, being developed 
on sandstones and shales. wStream dissection has made this area 
also very rough and broken. 
The Arkansas Valley represents a worn-down plain. Low residual 
hills and ridges rise above it, and its streams flow in valleys cut below 
the general level. 
Studies of the Ouachita Mountains by J. A. Taff" show thai the 
uplift of this range involves a thickness of nearly 5 miles of rock. 
aTaff, J. A., Structural features of the Ouachita Mountain Range in Indian Territory: Science, new 
sci., vol. 11, No. 2(i(i, Feb. 2, 1900, pp. 187-188. 
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