224 VLORIDA GEOLOGICAL SURV]-15FH ANNUAL RrPORF

 Gill' 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 crossbedded sediments in lagoons or other arms of the sea. Then, (luring 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 reworking the deposits and disseminating the clay substances more thoroughly 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 VWatkins, 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 influence, as iron compounds, is at first thought difficult to explain, especially in view of the fact 'that the deposits are distributed over a relatively 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'Gill, A. C., Oral Communication.
 2Rettger, R. E., Oral Communication.