PETROLEUM POSSIBILITIES OE FLORIDA 
61 
OLIGOCENE 
To the Oligocene are referred three formations, namely, the Mari¬ 
anna, Chattahoochee and Tampa. The Chattahoochee and Tampa forma¬ 
tions are suspected of being in part, at least, contemporaneous. The 
relation of the Marianna to the Chattahoochee has not been well estab¬ 
lished. 
MARIANNA FORMATION 
The Marianna formation is prevailingly a light-colored, granular 
limestone. It is known in Florida only in the limestone area west of the 
Apalachicola River where it overlies the Ocala limestone, and except by 
a study of the fossils is with difficulty distinguished from that formation. 
The Marianna is regarded as the equivalent of a part, at least, of the 
Vicksburg formation of Mississippi and Alabama. The Marianna is a 
thin formation; its full thickness has not been determined, but in the 
section at the public road crossing on the Chipola River at Marianna 
33 feet of this formation, according to Cooke, is exposed. In this sec¬ 
tion the base of the formation is seen, but some of the upper part prob¬ 
ably has been removed by erosion. 
CHATTAHOOCHEE FORMATION 
The Chattahoochee formation differs from the Marianna in that it 
contains an appreciable clay ingredient. It is in fact a clayey limestone 
containing relatively few fossils. This limestone is found exposed on 
and near the Apalachicola River at the Georgia-Florida state line and 
for some 12 miles down this stream and at a number of localities 
west of this river. It is seen again on the Ocklocknee River from the 
state line to the crossing of the Seaboard Air Line Railway. East of 
the Ocklocknee River it is found at the surface in places in Leon, Wa¬ 
kulla, Jefferson, Madison, Taylor, Lafayette, Dixie and Suwannee Coun¬ 
ties. It is apparently quite generally absent in central peninsular Flor¬ 
ida, where formations of later age in places rest directly upon the Ocala 
limestone. East of the Ocklocknee River the rock is a hard and rela¬ 
tively pure limestone, differing in this respect from the clayey phase of 
the rock as seen on the Apalachicola River. The thickness of the Chat¬ 
tahoochee formation is probably between 100 and 200 feet. 
