160 GEOLOGICAL SURVEY OF ALABAMA. 
posing them will be exposed in the valleys in parallel 
bands, the oldest formation in the central part or axis of 
the valley, while on each side of this axis, and dipping or 
sloping away from it in opposite directions (anticlinal), will 
occur in regular succession, the newer formations up to the 
highest. Thus, beginning with the Coal Measures on, say, 
the northwest side of such a valley and crossing it towards 
the southeast, we should pass in succession over the strata, 
all dipping to the northwest, of the Sub-Carboniferous 
Devonian and Silurian to the Cambrian, which, as the lowest’ 
of the geological series, would occupy the central area. 
Beyond this then would follow, on the other side of the 
axis of the anticlinal, the same formations, only in the 
reverse order, and dipping towards the southeast; thus 
Silurian, Devonian, Sub-Carboniferous, to the Measures of 
the Coal Field on that side. 
Now, as a matter of fact, simple, symmetrical, anticlinal 
structure is rarely seen in any of our valleys, the nearest 
approach to it in the region here treated of being east of the 
Blount Mountain, and east of McAshan Mountain, but in 
both these cases the full series is lacking on one side of the 
anticlina], by reason of a second fold or of a fault, as will 
be seen in the special description given further on. 
As a rule we find a prevalence of southeasterly dips even 
on the northwestern side of the anticlinals. This could 
come about only by the overlap of the fold in that direction 
and the compressing together of strata so that they all dip 
the same way; or by an overlapped fold combined with a 
fault. In the first case we should have a repetition of the 
strata on each side of the central area, while in the other 
case only a part of the constituent strata of the anticlinal 
would appear on one side of the anticlinal, the rest being 
hidden under the overthrust measures of the other side. A 
study of the map will show that the last named order of 
things prevails in the great majority of cases. 
Before going on to the special description of the valleys, 
it will be instructive to give a general section across the 
whole area of the map at a point where the structure is seen 
in its simplest form. 
The accompanying diagram showing a cross section from 
