34 FLORIDA GEOLOGICAL SURVEY-—SEVENTH ANNUAL REPORT. 
ficulty recognized from well samples. The term Tampa formation 
is here used as defined in the Second Annual Report of this Survey, 
1909. 
With regard to the exact equivalence in the Oligocene series, of 
the Tampa Silex beds and the Tampa limestone, there may be as yet 
some doubt. In their study of the geology and stratigraphy of Flor¬ 
ida published in the Second Annual Report of the State Survey, 
1909, Messrs. Matson and Clapp expressed the view that the 
Tampa formation of southern Florida is contemporaneous with the 
Chattahoochee formation of the Apalachicola River section. This 
view is supported also by Vaughan*. Dr. W. H. Dali, however, is 
of the opinion that the Tampa limestone is of later age than the 
Chattahoochee limestone.t While the determination of the relation 
of these beds is of importance in the study of the stratigraphy of 
Florida, the problem does not enter essentially into the study of the 
phosphate deposits. For this reason the correlation of these forma¬ 
tions will not be further discussed at this time, since for the present 
it is sufficient to recognize that the Tampa formation, as the term is 
here used, represents the earliest upper Oligocene deposits of south¬ 
ern Florida. 
THE ALUM BLUFF FORMATION. 
The Alum Bluff formation in Florida represents the'uppermost 
or latest of the Oligocene series. As now understood the formation 
is a very extensive one reaching from the Apalachicola River in 
west Florida, east and south through the peninsula to the Gulf, 
forming a broad belt lying north and east of the older formations 
previously described. 
The relation of the Alum Bluff formation to the Chattahoochee 
limestone of northern Florida as well as to the Tampa limestone of, 
southern Florida is probably throughout that of conformity, the 
change from the one formation to the other being gradual. The 
Alum Bluff, however, contains a larger amount of sand and clay 
than do the other formations, thus indicating a marked change in 
the conditions of deposition. Another notable feature of the Alum 
Bluff formation to 1 which reference will be made later, is the fact 
*Vaughan, T. W., a contribution to the Geologic History of the Floridian 
Plateau. Carnegie Institution of Washington, Publication No. 133, pp. 99-185, 
1910. 
tDall, W. H., U. S. Geol. Surv. Bull. 84, 1892; Wag. Free Inst. Sci., Vol. 3, 
Pt. 6, 1903; U. S. National Museum Bull. 90, 1915. 
