A PRELIMINARY REPORT ON CLAYS OE FLORIDA 
109 
ward, in a somewhat broken succession in Florida, to almost the ex¬ 
treme west end of the State. It is probably the most widespread forma¬ 
tion exposed in the State. 
The Jacksonville formation is a term applied to deposits known in 
the vicinity of Jacksonville and having a limited extent. Its fauna indi¬ 
cates a later age, but otherwise it closely resembles the Alum Bluff 
formation. 
The Choctawhatchee formation consists of marls, sands, and clays 
exposed in portions of west Florida. 
pliocene 
To the Pliocene are assigned several formations consisting essen¬ 
tially of marls, sand and clays representing marine and fresh-water 
conditions of sedimentation. Several of these formations are probably 
contemporaneous. 
pleistocene 
The Pleistocene deposits, which here includes those of Recent age, 
as well, are of widespread distribution and variable lithologic character, 
representing both terrestrial and marine conditions. They are found 
principally in the southern extremity of the State and along both the 
Atlantic and Gulf coasts. Numerous deposits of this age, while rela¬ 
tively thin, are widely distributed over the interior portions of the State. 
GEOLOGIC AGE, OCCURRENCE AND DISTRIBUTION OE THE CLAYS 
There is not space within the limitations of this report to treat 
exhaustively the geologic age of the clays of Florida. In reconnaissance 
work it is often difficult and at times impossible to ascertain the horizon 
to which a clay deposit should be assigned, owing to its frequently limited 
areal extent, lack of fossils and imperfect exposures. The geologic map 
issued with the Fourteenth Annual Report of this Survey (1922) has 
been largely conformed to in assigning clays to formations already es¬ 
tablished and somewhat widely distributed within the State. It is to be 
noted, however, that within an extended area of exposure of one forma¬ 
tion there may be numerous deposits of a more recent age. This is particu¬ 
larly true in Florida where the great number of sink-holes, swamps, and 
small streams of low gradient have afforded conditions favorable for the 
formation of clay deposits. Sellards 1 has pointed out that the sinks pos- 
1 Sellards, E. H., The Relation of the Dunnellon Formation to the Alachua Clay, 
Sixth Annual Report, Florida Geol. Survey, p. 162, 1914. 
