The Georgia Bauxite Def^osifs. — JJ'afsoii. 45 
coatings, the pisoliths were deposited on the borders of the 
basin, and the interstices were filled by minute ooliths formed in 
a similar manner or by the flocculent precipitate itself. Slight 
differences in the conditions prevailing in the several springs, 
such as concentration and relative proportion of the various 
salts in solution, also temperature and flow of the water, would 
produce the variation in the character of the ore observed at 
different points." 
The theory above outlined was originated and applied bv 
Dr. Hayes to the Georgia- Alabama deposits. It is here re- 
viewed and discussed at some length for the reason that after 
a careful study of the same region by the writer. Dr. Haves' 
theory more completely covers the essential features required of 
a satisfactory theory and explains the conditions in the field as 
the writer saw them, than any one yet advanced. 
Age of the Deposits. 
Dr. Hayes* has given an excellent presentation of the phys- 
iographic development of northwest Georgia, and the contigu- 
ous parts of Alabama and Teimessee. Hayes points out in this 
development three levels of planation in the bauxite area, the 
two oldest ones corresponding in age to the Cretaceous and 
Eocene periods, respectively. It is further shown that the sur- 
faces of the dolomyte plateau and ridges of the bauxite region 
determine the Eocene base-level plain, corresponding to an 
altitude of about 950 feet above sea level. The majority of the 
bauxite deposits where not deeply eroded are found between 
the levels of 900 and 950 feet. Since the altitude of the deposits 
corresponds closely to that of the Eocene peneplain, they could 
not have been formed previous to that time as the ore-bodies 
are shallow surface deposits. Xor could they have been 
formed after the plain was uplifted and eroded without chang- 
ing the place of deposition of the ore-bodies. This would 
apparently fix the age of the l)auxite deposits sometime near the 
close of the Eocene. 
•Op. cited, pp. 551-562. 
Physiography of the Chattanooga District, in Tennessee, Georgia, and 
Alabama. Nineteenth Annual Report, l'. S. Ceol. Survey, 1897-98 (1899), part 
ii, pp. 1-5S. 
