bckel.J ALABAMA. 61 
the Portland-cement materials of northern Alabama and of central 
and southern Alabama will be discussed separately, because there is 
a marked geologic as well as geographic distinction between the two 
portions of the State. 
NORTHERN ALABAMA. 
The raw materials for the manufacture of Portland cement occur- 
ring in the Paleozoic formations of northern Alabama arc limestones, 
ales, and clays. The limestones belong mainly to the Mississip- 
pian ( wi Lower Carboniferous") and to the Chickamauga formation, the 
hales to the Pennsylvanian ("Coal Measures"), and the clays to the 
Cambrian, Mississippian, and Pennsylvanian. Although these mate- 
rials have not yet been utilized for Portland-cement manufacture in 
Alabama, they have been so used in other States, and there is no reason 
to doubt that the future will witness their utilization in Alabama. 
GENERAL GEOLOGY. 
In northern Alabama the combined effects of geologic structure and 
erosion have resulted in certain definite topographic types with which 
the geologic outcrops are closely connected. 
Structurally, northern Alabama is made up of a series of parallel 
synclines and anticlines, trending usually a little north of east. The 
anticlines are sharp, narrow folds; the synclines are fiat, wide basins. 
The effect of erosion has been to cut awa}- the synclines, and the 
streams of the region now run along anticlinal valleys bordered by 
flat topped synclinal plateaus. 
The plateaus throughout most of northern Alabama are capped by 
conglomerates, shales, and sandstones of the Coal Measures. The 
Mississippian limestones commonly outcrop along the sides and at the 
immediate base of the plateaus. The Ordovician (" Lower Silurian") 
beds occur as long, narrow outcrops in the valleys. The middle of 
the valley is usually occupied by Cambrian shales and the Knox dolo- 
mite. The Chickamauga limestones would formally outcrop as two 
parallel bands in each valley — between the middle of the valley and 
the foothills of the plateaus. Faulting has, however, been so common 
that only one of these bands is usually present, the other being cut out 
by a fault. 
LIMESTONES. 
CHICK AM A VGA LIMESTONE. 
The Chickamauga limestones outcrop in Alabama in three principal 
areas. In the Tennessee River Valley some of the smaller streams 
which flow into the river from the north, like Flint River, Limestone 
Creek, Elk River, Bluewater Creek, and Shoal Creek, have eroded 
their vallevs into the Chickamauoa limestone. These areas are crossed 
