GEOLOGY CHOCTAWHATCHEE AND APALACHICOLA RIVERS. 89 
may -be referred provisionally to the Claiborne. These exposures, 
which may be seen for about one and three-fourth miles below the 
State line, probably represent the. upper part of the Claiborne, since 
limestones of later age come into the section only a few miles 
farther down stream. It is probable that this formation is reached 
by many wells in the northern part of this area. 
STRUCTURE. 
In his report on the Coastal Plains of Alabama, Dr. Smith has 
shown that the normal line of outcrop of the Claiborne deposits 
on the Choctawhatchee River lies near the north line of Geneva 
County, Alabama, and hence some miles north of the Florida line. 
The recurrence of these deposits at Geneva is interpreted by Dr. 
Smith as indicating an interruption in the rate of dip amounting 
to a fold in the rocks. This interpretation of the structure, an- 
nounced in 180/L, so far as the writer is aware, has not been ques- 
tioned. With regard to the exposures in Florida, it is observed 
that the clip to the south carries the formation below water level 
in the river within a short distance south of the Alabama-Florida 
State line. 
OCALA FORMATION. 
The Ocala formation, which consists chiefly of very pure lime- 
stones, has been identified by Dr. C. W. Cooke at several exposures 
on the Chipola River near Marianna. One of these exposures 
which has been described by Cooke is that at the public road cross- 
ing one-half mile east of Marianna.* The Ocala limestone at this 
rface has a thickness of about ten feet or more above water level. 
Elsewhere in this area die Ocala formation has not been' sepa- 
rated from the lithologically similar limestones of the overlying 
Vicksburg formation. 
STRUCTURE. 
The Ocala formation dips to the south and passes below water 
level in the Chipola River probably not far below Marianna. On 
the Chattahoochee River, according to the observations of Cooke 
and Shearer the formation remains above water level to a point 
* The A^e of the Ocala Limestone, by Charles Wythe Cooke, U. S. Geol. 
Srirv., Prof. Paper, 95-I, 1915. 
