28 GEOLOGICAL SURNEY OF ALABAMA. 



including this rock, and possibly some strata above it, in the 

 Upper Cambrian. It is one of the most prominent forma- 

 tions exposed in this valley. In descending the valley it is 

 first brought to the surface in Sec. 5, T. 13, R. 2, east. A 

 few miles farther down, 1,200 feet of it is exposed* This 

 deep exposure extends down to the Blackburn Fork of the 

 Little Warrior. Below this it is less prominent; and it 

 passes entirely beneath the surface in Sec. 12, T. 14, R. 1, 

 west. It is barely seen at any point from here, to a little 

 below Turkey Creek in Jefferson county. This rock is 

 prominent in many parts of Jones' Valley, in the Cahaba 

 Valley, and especially so in the upper Coosa Valley. It is 

 occasionally brought to the surface in Will's Valley, but not 

 in the Sequatchee fold, at least below the Tennessee river. 



The amount of denudation that has taken place in the 

 deepest parts of this valley is thus shown by these measure- 

 ments and estimates of thickness of strata to have been about 

 5,300 feet, or a little more than one mile in vertical depth. 



STRUCTURE. 



It is, however, to the geological structure and mineral re- 

 sources of this valley that the attention of the reader is 

 specially directed, both on account of the peculiarities of the 

 former and the importance of the latter. 



THE GREAT ANTICLINAL FOLD. 



Murphree's Valley, like the other Silurian valleys of 

 North-east Alabama, is a valley of elevation ; that is, a val- 

 ley eroded out of the crest of an upward fold of the strata. 

 It is not within the scope of this report to examine or en- 

 quire into the causes or processes of such folds, or such val- 

 ley-making erosions. Upon these there might well be much 

 difference of opinion among geologists, and the unprofes- 

 sional reader would not be benefitted by mere speculation. 



