120 THE CLAYS OF ARKANSAS. 
JOHNSON COUNTY. 
GENERAL GEOLOGY. 
The geology of Johnson County is similar in its broader features 
to that of Pope County to the east, of Franklin on the west, and of 
Logan on the south. The rocks are of the same geologic age, but there 
are not the same strong contrasts between the different formations 
that characterize either Pope or Logan counties. The rocks are 
chiefly sandstones, shales, and coals. The lowest rocks in the county 
are exposed in the bottoms of the narrow valleys of the northern 
part of the county, on the headwaters of Mulberry River and of 
Little Piney Creek, and about Fort Douglas on Big Piney Creek. 
The rocks of the lofty mountains about Melson, Ozone, and Mount 
Levi, although they are much higher than those of the valleys about 
them, are nevertheless geologically lower than the coal-bearing beds 
of the Arkansas Valley about Clarksville and Coal Hill. 
CLAY DEPOSITS. 
CLAY SHALES. 
The clays and clay shales of Johnson County that are likely to have 
economic value lie along the line of the Little Rock and Fort Smith 
Railway and along or near Arkansas River. The shales of other 
parts of the county are just as good intrinsically as those near trans- 
portation, but owing to the expense of getting them into market 
they are necessarily of less importance. For this reason but little 
is said here in regard to the clays and clay shales of the more remote 
parts of the county. 
The Hartshorne sandstone bed, which forms Ouita Ridge, in Pope 
County, continues westward into Johnson County, forming the broad 
ridge east and north of Piney station. Those same sandstones con- 
tinue northward through the eastern section of R. 22 W. South of 
Arkansas River this sandstone forms the great ridge 2 miles due 
south of Piney station. The Spadra shale, containing the Ouita coal 
bed, forms a narrow trough south of Piney station. This trough 
widens abruptly toward the west and north, so that the Spadra shale 
underlies all the country west of Piney and west and north of Knox- 
ville for 8 miles or more. These same shales are exposed in the lower 
portions of the hills east and south of Clarksville. along the valley of 
Spadra Creek, west of the mouth of that stream to Spadra and Mon- 
tana, about the base of Spadra Hill, at Hartman, and along the base 
of the hill just north of Hartman. Throughout this entire area of 
the Spadra shale clay shales available for the manufacture of paving 
bricks, sewer pipe, and fire-clay goods may be found, and at many 
places they are conveniently exposed. 
