530 



W. A. NELSON APPALACHIAN BAUXITE DEPOSITS 



One of the major thrust-faults of the region, having a low angle of 

 thrust to the northwest and having its strike in a north 30 degrees east 

 course along the west side of the crest of Missionary Eidge, has thrust 

 over the closely compressed fold, of Silurian and Ordovician rocks, the 

 cherty Knox dolomite of Canadian and Ozarkian ages. 



The bauxite deposits occur on the east side of Missionary Eidge, a 

 short distance below the crest, at a point where the line of the thrust- 

 fault is still very near to the surface. 



At this point, which was at the time of formation of the bauxite an 

 old peneplain, the ground-water circulating upward along this fault 

 readily came to the surface through the few feet of fractured chert and 

 dolomite lying between the fault-plane and the ancient land surface on 

 which these underground waters came forth. 



Bentonite and Bauxitk 



The bentonite layer outcropping at the top of Bragg's quarry dips 

 underground to the eastward and, as is shown by the accompanying cross- 



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Figure 2. — Bed of Bentonite 



The bed outcrops at the top of the Bragg limestone quarry, East Chattanooga, 

 Tennessee. Photograph by Wilbur A. Nelson. 



section, quickly turns upward and is cut off by the thrust-fault just above 

 which is now found the bauxite deposits. 



The bentonite outcropping just five-eighths of a mile to the west of 

 the Kalbfleisch bauxite mines measures 40 inches in thickness. It rests 

 oil the massive pure limestone of the Lowville formation and is overlain 



