224 FLORIDA GEOLOGICAL SURVEY-I 5 TH ANNUAL REPORT 
Gill 1 suggests that the formation of this clay-bearing sand may 
have occurred in the following manner: Spring floods carried quartz 
sand and mica to the peninsular region where it was deposited as cross- 
bedded sediments in lagoons or other arms of the sea. Then, during 
the seasons of less rainfall, the streams emptied milky water with the 
clay substance in suspension into the areas containing the sand. The 
clay substance was then deposited as a thin coating over relatively thin 
layers of sand. The lagoons were more or less quiet during the drier 
seasons, but during the periods of freshets the additional quantities of 
water caused conflicting currents, which assisted to some extent in re¬ 
working the deposits and disseminating the clay substances more thor¬ 
oughly throughout the sand. Alternate deposition of quartz-sand and 
milky water with alternating seasons caused the intimate admixture of 
sand and clay and the accumulation of the present thickness of it. 
It is not only possible, but probable, as is suggested by Watkins, that 
this material was first deposited as Cretaceous sediments near the base 
of the granitic area, the ultimate source in the Appalachian region, and 
these beds were later eroded to supply the sediments for the deposits 
as now known in Florida. As is also pointed out by both Watkins and 
Davis, this would account for the higher plasticity of the Florida clays 
than the present Cretaceous clays of Georgia. 
Conditions of sedimentation, in which coarse pebbles, varying from 
three-fourths of an inch to less than a pin-head, could be intimately 
mixed with mica and finely divided clay, as this material is, and yet be 
so free from other substances, particularly those exerting a coloring in¬ 
fluence, as iron compounds, is at first thought difficult to explain, espe¬ 
cially in view of the fact that the deposits are distributed over a rela¬ 
tively large area. Rettger, 2 however, points out that the deposition of 
this material is not necessarily very different from any other sandstone. 
The clay-bearing sand is an unconsolidated sandstone in which the clay 
content ranges from twenty to forty per cent. Many sandstones have a 
similarly high clay content. 
If shoreline conditions similar to those of the present are postulated 
for Florida during the time when this formation was being deposited, 
which was probably Pliocene, with large arms of the sea, relatively shal- 
1 Gill, A. C., Oral Communication. 
2 Rettger, R. E., Oral Communication. 
