GENERAL C OX CLU SIGNS * 539 



after the solution was made the sample was filtered. The alumina ob- 

 tained was 2.20, or 0.11 gram. The percentage of (AlgOg) alumina 

 precipitate to the entire alumina in bentonite was 11 per cent. In this 

 sample the ratio of tannic acid to alumina is 10, or twice as great as in 

 an}'' of the 8^-month tests; 3'et the percentage Al^Og is 11 per cent, 

 which follows the ratio as shown above, excej^t the results in this case 

 seem excessively high. 



Geneeal CoxcLrsioxs 



These experiments show that the bentonite may very readily be the 

 source of the alumina in the bauxite deposits of the Appalachian region. 

 It is known that this bentonite bed occurs from Birmingham on the south 

 to Ohio on the north and probably over the entire area of the Lowville 

 sea;^^ wherever these bentonite beds occur in a faulted region, not far 

 below the surface of one of our old or recent peneplains, one might well 

 look for bauxite deposits. 



It is considered that the Chattanooga district bauxite deposits obtained 

 their alumina from the bentonite beds of Ordovician age, and that the 

 deposits were formed on an old peneplain at the beginning of the 

 Pleistocene period. 



Discussion 



C. A. Bonine: I would like to ask Mr. Nelson to clear up a matter 

 for me. Is the dolomite older than the rocks thrust over on it ? 



Nelson: Yes. 



BoNiNE : How does bentonite get over the surface ? " 



Nelson : That is not bentonite. It is bentonitic material mixed with 

 bauxitic material. 



A. C. Lane: One of my students found a sample with characteristic 

 sign of oxide deposits in this region. 



13 Wilbur A. Nelson : Volcanic ash-bed in the Ordovician of Tennessee. Kentucky, and 

 Alabama. Bull. Geol. Soc. Am., vol. 33, 1922, pp. 605-616. 



