A PRELIMINARY REPORT ON CLAYS OV VLORIDA 115

ton and Walton counties. It consists of a marl member which is overlain by a grayish clay. The clay ranges in thickness from about ten to approximately thirty feet. This clay is the southeastward extension of the Pascagoula clay which is exposed through portions of the Gulf states to Eastern Texas.
 The Charlton formation is a marine Pliocene marl extending along the northwest side of Nassau County next to the St. Marys River. It is not known to be associated with clays.
 The Nashua formation, also Pliocene, consists of interbedded mars and clays and occupies a small area in Volusia, Flagler and Putnam counties. The clays are usually o~f limited extent and frequently thin Some of these are calcareous and all are to some extent sandy. Many, however, may be used for structural materials. Several of these clays have formerly been used in the manufacture of common brick.
 The Caloosahatchee formation, likewise a marine Pliocene marl, underlies a small area on the Pinellas. peninsula on the west side of Tampa Bay, and a much larger area in the 'region of the Caloosahatchee River. A few calcareous clays accompany the marl.
 The Bone Valley formation, Pliocene, occupies a limited area east of Tampa in Polk, Hillsborough, Manatee and Hardee counties. It is a fluviatile deposit chiefly noted for its pebble phosphate content and is extensively worked for phosphate in this region. It also contains a sandy clay known throughout this region as the Bartow clay. This term was formerly applied to the matrix carrying the pebble phosphate, but now the application of the term is limited to the sandy clay overlying the phosphate horizon. The Bartow clay is widely distributed in this region and is used to some extent as a road-surfacing metal. Its high sand content greatly reduces its plasticity, making molding and handling difficult. When burned, however, it is suitable for common brick.
 The Alachua clay is a terrestrial Pliocene formation composing small disconnected areas in central Florida. This term was -formerly used to designate deposits of a blue to gray sandy clay which. had accumulated in sinks and ponds during Pliocene times and encased numerous vertebrate remains. It is now understood to include also the hard rock phosphates formerly known as the Dunnellon formation. The Alachua clay formation contains many local clay deposits in Alachua, Levy and Marion counties.
 The Zitronelle formation, a Pliocene deposit extending through the Gulf states has only a limited extent in Florida. It extends through