10 FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
The interstices and cavities of the rocks below the water line are 
filled with water, the limestone being an important water-bearing 
formation. 
The areas in which the soils are derived solely from the Vicks¬ 
burg are limited in extent, yet through the drainage and other con¬ 
ditions arising from the presence of this formation the soils are 
modified over large areas in the central part of peninsular Florida, 
as well as in parts of the westward extension of the State. 
In western Florida the Vicksburg formation is exposed at the 
surface in places in the northern part of Jackson, Washington, 
Holmes and Walton Counties. In Jackson County the exposures are 
extensive along the Chipola River from near the north line of the 
State to several miles below Marianna. From the Chipola River 
west to Holmes Creek the Vicksburg lies near the surface and is 
locally exposed at the surface. Along the northern border of the 
State surface exposures occur as far west as the Natural Bridge in 
the northeastern part of Walton County. The southern line of sur¬ 
face exposure in western Florida is thus seen to extend from Nat¬ 
ural Bridge in Walton County in a southeaster!y direction, reach¬ 
ing its greatest southward extension along the tributaries of Holmes 
Creek in Washington County and the Chipola River in Jackson 
County. From the Chipola River the line of surface exposure bends 
northeast, crossing the Chattahoochee River above its union with 
the Flint River. 
To the southwest, south, and southeast of this line the Vicksburg 
dips beneath later formations. At Pensacola the Vicksburg has 
not been reached by wells exceeding 1,000 feet in depth. As Pensa¬ 
cola is less than 100 miles southwest of the nearest surface exposure 
of the Vicksburg in Walton County a dip is indicated exceeding an 
average of ten feet to the mile in that direction. Although well ex¬ 
posed along the Chipola River in Jackson County for some miles 
above and below Marianna, yet directly east of Marianna the forma¬ 
tion is not reached by the Apalachicola, notwithstanding the fact 
that this river cuts deeper than the Chipola River. The formation 
is found, however, along the Chattahoochee River, a tributary of the 
Apalachicola, northeast of Marianna. 
Beyond the limits of the surface exposure of this formation its 
influence is still evident in the formation of occasional sink holes 
and circular lakes, of which the lake at DeFuniak Springs is an 
illustration. The lakes of central Washington County and of the 
southwestern part of Jackson County probably have a similar ori¬ 
gin. The basin of Lake Ocheesee in the southeastern part of Jack- 
