A PRELIMINARY REPORT ON CLAYS OF FLORIDA 221

 GEOLOGIC AGE
 The age of the sedimentary kaolin is not known. Matson1 places it provisionally in the Pliocene with a query. Ries2 lists it under the Oligocene clays, but explains that its position in the Tertiary system is not known. Watkins3 says, "geologically, this area belongs to the Apalachicola group of Oligocene age." The formations in the general region about the sedimentary kaolin occurrences were formerly included in the Apalachicola group of Oligocene age. At present, however, the Alum Bluff formation, formerly considered a part of the Apalachicola group, is regarded as Miocene. This does not necessarily mean that the sedimentary kaolin is of the same age.
 Sellards4 says: "The place of the clay-bearing formation in the geologic time-scale is difficult to determine owing to the complete absence of fossils. It overlies the Oligocene limestones. There is also some reason for believing that it lies at a stratigraphic level higher than the fuller's earth beds and hence is not older than the Miocene. However, inasmuch as no one of the later formations is found overlying this formation, it is not possible to fix its age more definitely."
 The fact that the clay formation is found overlying the fuller's earth confirms the belief that it is at least younger than that stage of the Alum Bluff when the fuller's earth was deposited.

 ORIGIN
 The origin of the sedimentary kaolin has not as yet been satisfactorily explained. The beds are, without doubt, sedimentary, as is indicated by the cross-bedding within the clay-bearing sand; by the fact that the various substances, such as green clay, fuller's earth, limestone, etc., underlie the sand; and by the conglomeratic texture and the presence of water-worn pebbles in the material itself. This formation is apparently everywhere separated from the underlying formations by an unconformity.

 1Matson, G. C., The Clays of Florida, U. S. Geol. Survey Bull. 380, p. 353, 1909.
 2Ries, H., High Grade Clavs of the Eastern United States, U. S. Geol. Survey Bull. 708, p. 289, 1922.
 3Watkins, Joel H., White-Burning Clays of the Southern United States, Trans. A. I. M. E., Vol. 51, p. 481, 1916.
 48ellards, E. H., The Clays of Florida, Journal American Ceramic Society, Vol. I, p. 318, 1918.