174 GEOLOGICAL SURVEY OF ALABAMA. 
graphs, to the Blount Mountain synclinal above spoken of, 
and to the fact that the fault which borders this synclinal 
on the eastern side extends with constantly diminishing 
amount of displacement, only a short distance beyond East- 
lake, where it gradually passes into the unbroken or un- 
faulted anticlinal of Clayton’s Cove. In this way the Knox 
Dolomite of both anticlinal and synclinal are brought into 
juxtaposition, while further to the south, where the amount 
of displacement in the fault is greater, the two are separated 
by the belt of Cambrian Shales presently to be spoken of. 
Next to the Knox Dolomite, going still across the valley, 
we come to the Cambrian formation, here represented by 
the Coosa Shales, a series of thin-bedded limestones with 
clay partings that make level, flat, badly drained lands with 
heavy impervious clay soils, commonly known as “Flat- 
woods.” The flatwoods limestones are usually very much 
folded and contorted, and stand often nearly vertical, for 
which reason they were spoken of by Prof. Tuomey as the 
vertical limestones of the valley. We usually see the upturned. 
edges of these limestone bands outcropping in the flatwoods 
in parallel rows, sometimes running without serious breaks. 
for long distances. At McCalla Station, Bessemer, Powderly, 
and in parts of Birmingham, this limestone may be seen. 
and easily recognized. These are the lowest in a geological 
sense, of the rocks brought up by the anticlinals and faults. 
in our valleys, and are the oldest of the rocks of Alabama 
about whose age we can be perfectly sure. In a regular 
symmetrical anticlinal, in which these Cambrian strata 
were exposed by erosion, they would, as a matter of course, 
occupy the central area, and this is in reality the case in. 
that part cf the valley between McCalla Station and Tan- 
nehill ; but in the far more common case, where the anti-. 
clinal is pushed over to the northwest and the steeper slope: 
occurs on that side, and still more plainly, where a break 
occurs along the crest of the anticlinal and the strata on 
the southeastern side are slipped up over those on the 
northwestern, the Cambrian strata are to be found no longer: 
in the geographical center of the valley, but far over on its: 
northwestern side. 
The Cambrian belt above described, thus marks the limit. 
