A PRELIMINARY REPORT ON CLAYS OF FLORIDA 117

Limestone, Miami Oolitic Limestone, and the Palm Beach Limestone, and are found in the extreme southern portion of the peninsula. No known clay deposits are associated with them.
 There are many alluvial and lacustrine deposits of clay and claybearing sands throughout the State. These are principally Pleistocene and Recent, yet a few of them may have been formed during the Pliocene period. These undifferentiated deposits lie chiefly along the floodplains of the larger streams.
 Extensive flood-plain deposits are found in the valley of the St. Johns River extending from Volusia County northward to Jacksonville. Many of these clays have never been worked and many more of them are capable of being utilized for various grades of structural materials. Former brick plants have been located near DeLand, DeLeon Springs, Denver, Palatka, Rice Creek, and Middleburg. Most of the clays found in this region are sandy, but some of great purity are found. Similar deposits are found in the vicinity of Kings Ferry. On the Ocklocknee River two brick plants (Ocklocknee Brick Co. and Tallahassee Pressed Brick Co.) now in operation, are using flood-plain clays. On the Apalachicola River several deposits of good quality are known and one of them is being worked at Blountstown.
 The sedimentary kaolin found in several points in central Florida is of uncertain age. It will be discussed more fully in a subsequent chapter. Numerous- lacustrine deposits will be discussed in the detailed description of deposits in the following chapter.

 CONDITIONS OF SEDIMENTATION AND SOURCES OF MATERIAL
 A complete geologic understanding of the clays of Florida involves a study of the geology of adjoining states. It also involves a review of the geologic processes that have been operating in Florida through the evidences by which these processes have been interpreted. Clay is always a secondary product; that is to say, it is always the result of decomposition and disintegration of pre-existing rocks. Igneous rock is the ultimate source of all other rock and therefore is the primary source of all clays.
 No igneous rocks are known to occur in Florida and in view of the geologic conditions under which the Floridian land mass was formed, the probabilities of encountering igneous rock at any reasonable depth