go FLORIDA GEOLOGICAL SURVEY ELEVENTH ANNUAL REPORT. 
some few miles above the confluence of this river with the Flint 
River.* 
OLIGOCENE. 
MARIANNA FORMATION. 
The Marianna formation, the type locality of which is at Mari- 
anna, Florida, includes chiefly limestone similar in appearance to 
those of the Ocala formation. These limestones are extensively 
exposed in the vicinity of Marianna. Other limestone exposures 
representing either this formation or the Ocala formation are fre- 
quent over much of the northern part of the area. At Marianna 
the limestone of this formation has a thickness as shown by the 
section made by Cooke of 33 feet. On the Choctawhatchee River 
limestones are occasionally exposed from a few miles south of the 
State line to within one or two miles of the crossing of the Louis- 
ville & Nashville Railway at Caryville. To the south of Caryville 
this limestone fails to show in the river banks and presumably has 
dipped below water level. 
STRUCTURE. 
On the Chipola River the Marianna formation remains above the 
water level for some miles below Marianna. In the area intervening 
between the Chipola and Choctawhatchee Rivers limestones of either 
Eocene or Oligocene age are found occasionally exposed as far south 
as the vicinity of Wassau in Washington county. The recorded ex- 
posures of these formations indicate a pronounced extension of these 
limestones into Florida in a general northeast-southwest direction, 
the maximum southward extension being near or somewhat west 
of the central part of this area. 
CHATTAHOOCHEE FORMATION. 
The Chattahoochee formation which includes chiefly lime- 
stones more or less impure from clay inclusions is well exposed on 
the Chipola and Apalachicola Rivers. The sections which best 
represent this formation on the Apalachicola River have already 
* Deposits of Claiborne and Jackson Age in Georgia, by Charles Wythe 
Cooke and Harold Kurtz Shearer, U. S. Geol. Surv., Prof. Paper, 120-C, 1918. 
