8 FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
LOWER OLIGOCENE. 
THE VICKSBURG LIMESTONE. 
The Vicksburg Limestone is an extensive formation, which, 
although exposed over only a limited area, underlies the entire 
State. As a formation it is not confined to Florida, but extends 
into Georgia, Alabama, Louisiana and Mississippi, being exposed at 
the surface, or reached by well borings over parts of each of these 
States. In literature the reader will find the terms Marianna, 
Peninsular, and Ocala limestones used for phases of the Vicksburg 
formation. Some doubt remains as to whether these terms apply to 
actual well marked divisions of the Vicksburg, or merely to varying 
phases of that formation. In its relation to soils it will not be neces 
sary to describe separately these subdivisions of the formation. 
While the Vicksburg Limestone varies in its lithologic charac 
ters it is prevailingly light colored and highly fossiliferous. As a 
rule it is a soft white limestone which crumbles easily and has a 
granular appearance. Locally, however, it may be close grained, 
compact and hard, and may be dull colored, or have a pinkish cast. 
Locally, also, the formation contains masses or layers of flint. 
These often occur as “hog backs’’ in the formation giving much diffi 
culty in mining the rock, and in drilling wells. The flint as well as 
the compact phase of the limestone is due to deposition from solu¬ 
tion by underground water. At Marianna, the type locality of the 
“Marianna” phase of the formation, the limestone is particularly 
soft and is there sawed into blocks of convenient size, as taken from 
the earth, and is used for chimneys and for building purposes. Upon 
exposure the limestone hardens. This is due to the fact that the 
water filling the interstices of the rock holds calcium carbonate in 
solution and this is precipitated as the water evaporates, and acting 
as a cement, hardens the rock. 
The formations which lie above the Vicksburg rest unconform- 
ably upon it apparently indicating erosion of this formation previ¬ 
ous to the deposition of the later formations. In addition to these 
irregularities there are further irregularities from subsequent ero¬ 
sion due to solution by underground water. This dissolving effect 
of underground water is continuously operating. Where the lime 
stone lies near the surface the results are observed in solution 
basins, underground cavities, and numerous sinks.* 
*For a description of the lake basins formed by solution, see Third An¬ 
nual Report, pages, 43-76, 1910. A description of the sinks, underground 
channels and disappearing streams will he found in Bulletin No. 1 of the 
Survey Report, 1908. 
