526 AV. A. XELSOX— APPALACHIAX BAUXITE DEPOSITS 



ary Eidge section, lying just east of the city, to see if the bed of altered 

 Yolcanic ash, the bentonite, which should occur in the Ordovician rocks 

 on the west side of Missionary Ridge, was present. 



The area in East Chattanooga lying at the west foot of the ridge and 

 directly to the west of the large bauxite mines of the Kalbfieisch Chem- 

 ical Corporation was visited and a fine exposure of the bentonite found 

 at the top of Bragg's quarry, located at the intersection of Bragg Street 

 with the Southern Railway, and later a good exposure was found in the 

 yard of the Avondale school, about five-twelfths of a mile farther south. 

 Two-thirds of a mile east of these outcrops occur the bauxite mines of 

 Missionary Ridge. 



Physiography 



In the Chattanooga area there are a number of well defined peneplains, 

 and it is thought that one of these played an important part in the for- 

 mation of the bauxite. They present a most striking aspect when viewed 

 from Lookout Mountain, the top of which is the highest of these old 

 plains. It was called the Cumberland tableland by Safford.^ This pene- 

 plain has been considered as of Carboniferous age by Hayes. ^ Going to 

 the east, we find as the next lowest level the top of White Oak Mountain, 

 with an elevation of from 1,300 to 1,500 feet. From White Oak 

 Mountain on the east, to Waldens Ridge on the west, is a distance from 

 12 to 18 miles, and in this interx^ening area are located a number of low- 

 lying ridges of different elevations and the main valley of the Tennessee 

 Hiver. A study of the region shows that Missionary Ridge, with an 

 elevation of 1,000 feet above sealevel, may represent the remnant of 

 another peneplain, and that a series of parallel ridges whose crests are 

 all of approximateh' the same elevation (850 feet), and which lie between 

 Missionary Ridge and the White Oak Mountain, is the most recent pene- 

 plain of this section, with the exception of the present plain of the 

 Tennessee River, with an elevation at Chattanooga of 670 feet. 



It is the old peneplain, now lying at an elevation of approximately 

 850 feet, which particularly interests us in our study of the origin of the 

 bauxite deposits, for the bauxite occurring on the east side of Missionary 

 Ridge is found at this elevation. At that geologic time the present topog- 

 raphy would indicate there existed between Missionary Ridge, on the west, 

 and White Oak Mountain, on the east, a broad, fiat, featureless plain, 

 8 to -10 miles wide, with swamps occurring along the eastern base of what 

 is now Missionary Ridge. Bordering the banks of a might}' river then 



- J. M. Safford : Geology of Tennessee, 1869, p. 10. 



^ C. W. Hayes : Sixteenth Annual Report, U. S. Geol. Survey, part ill, 1895, p. 592. 



