MURPHREE'S VALLEY; ECONOMIC GEOLOGY. 39 



dip of the strata is away from the axis of uplift. The fold 

 ended where the valley ends. In the broad table lands be- 

 yond it there is no evidence of rupture or uplift. No ridge 

 or fold or fault is visible ;* there is no sign of disturbance 

 save a gentle dip to the north west, in this long and broad 

 expanse of table land, which extends from the end of this 

 valley to the Tennessee river. 



ECONOMIC GEOLOGY. 



Having thus given a general outline description of the 

 valley, showing its structure and the present arrangement of 

 the various formations exposed, a detailed description of its 

 minerals and materials of economic value will be better 

 understood. Of these, iron ore is the most prominent. It 

 exists in two forms, the Red Hematite of the Clinton forma- 

 tion and the Brown ore or Limonite, found at several 

 horizons, from the top of the Cambrian to the base of the 

 Coal Measures. They must be presented separately, and 

 the Clinton demands the first- place because of its greater 

 importance. 



HEMATITES OF THE RED MOUNTAIN OR CLINTON FORMATION. 



The Clinton is the great iron bearing formation of Ala- 

 bama and other states. It lies here comformably on top of 

 the Trenton limestone, and is capped with the Black Shale. 

 Its aggregate thiekness varies from place to place, but gen- 

 erally approximates 150 feet. The upper twenty feet, how- 

 ever, contain no valuable seams of iron ore. A vertical sec- 

 tion will show the average structure. 



*The fault spoken of elsewhere as cutting through the rim at or near the 

 head of the valley, cannot be followed very far beyond the rim of the valley. 



E. A. S. 



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