178 GEOLOGICAL SURVEY OF ALABAMA. 
Although so entirely different in topography and in gen- 
eral appearance, this part of the valley is itself also formed 
by a double anticlinal with synclinal between, as may be 
seen from the following description; proceeding from the 
eastern Red Mountain near McCalla Station towards the 
northwest across the valley, we pass first over a regular 
symmetrical anticlinal, the central line of which, marked by 
the outcrop of the belt of Cambrian rocks, is near the center 
of the valley, and is the formation upon which the Alabama 
Great Southern Railroad track is laid, from Tannehill up. 
McAshan Mountains is the counterpart of the eastern Red 
Mountain on the other side of the anticlinal, its strata dip- 
ping to the northwest as the beds of the eastern mountain 
dip to the southeast. On the other side of McAshan, 
however, we come to the fault mentioned, and the beds of 
the McAshan appear to dip northwest under the Knox 
Dolomite on the other side of the fault, showing that we 
have here again an instance of thrust fault in which the 
strata on the southeast side have been shoved under those on 
the northwest side. 
Southwest of the end of the McAshan Mountain we see 
again a recurrerce to the usual type of structure in this 
valley, viz., an overlap of the strata on the southeast side 
upon those to the northwest of the fault. As we have said, 
however, the geological structure in this lower part of the 
region of the map is not always to be clearly made out, for 
the reason that it is not possible to trace out the outcrops 
of the different formations because of the great mass of over- 
lying and more recent beds of the Cretaceous. The central 
part of the valley in this latitude is so generally covered by 
these beds that we can only indicate here and there the 
points where the underlying rocks are uncovered. 
In the vicinity of Woodstock there appear to be two areas 
of Cambrian rocks, the one at the station itself, where the 
shaly limestones have been exposed in the cut made by the 
Cahaba Coal Company for their railroad, and -the other a 
mile or two to the north, along the line of the Birmingham 
Mineral Railroad, just beyond the Edwards ore banks. The 
region between the two, so far as we are in condition to 
judge, is occupied by Knox Dolomite. 
