66 
FLORIDA GEOLOGICAL SURVEY—I 4 TH ANNUAL REPORT 
mined. These surface deposits were originally referred to the Lafay¬ 
ette, but there are some reasons for regarding a part of this material as 
merely the residue from the Alum Bluff formation. In Gadsden County, 
as well as in some other parts of the state, these red sands and sandy 
clays, the distribution of which is not indicated on the geologic map, 
attain a considerable thickness. 
The marine and fresh-water Pleistocene of extreme southern Florida 
has been represented in some detail on the map previously published by 
the Survey, and in this part of the state this earlier map has been fol¬ 
lowed without alteration. 
In the interior of the state there is, with little doubt, much Pleistocene 
that should be represented on a detailed map, but since in a report on 
the oil possibilities we are scarcely concerned with the thin surface 
formations, the Pleistocene of the interior of the state will not be further 
discussed at this time. 
The distribution of the Charlton formation, as shown on this map, is 
essentially in accordance with the description of the formation given by 
Stephenson and Veatch in their report on the geology of Coastal Plain 
of Georgia. 1 
No attempt has been made to map the Alachua formation. These de¬ 
posits are relatively thin and rest upon the Eocene of central peninsular 
Florida. For a map showing the distribution of this formation, refer¬ 
ence may be made to the Fifth Annual Report of this Survey. Like¬ 
wise no attempt has been made to separate the Jacksonville and Alum 
Bluff formations in northeastern Florida. 
The mapping of surface materials of the Lake Region of peninsular 
Florida presents considerable difficulty. The superficial deposits in 
the Lake Region, in peninsular Florida as far south as Highlands Coun¬ 
ty, consist of sands, gravels and clays, and in places kaolin beds, the age 
of which is undetermined. It is known that in some localities materials 
of this character overlie the Alum Bluff Miocene, or at least the fuller’s 
earth horizon of that formation. It may be, however, that these mate¬ 
rials represent the uppermost part of the Alum Bluff formation, or they 
may be a part of the Upper Miocene or Pliocene, or even possibly Pleis¬ 
tocene. In the absence of fossils, the determination of the age of these 
sediments presents unusual difficulties. Nor can it be asserted that the 
iU. S. Geol. Surv., Water Supply Paper No. 341, 1915. 
