114 FLORIDA GEOLOGICAL SURVEY-15TH ANNUAL REPORT

 Sandy soil ........... ...................................... feet
 Brown and gray sand with clay................................ 3 feet
 G ray clay .................................................... 3 inches
 W hite and green sandy clay................................... 3 feet
 G reen plastic clay ............................................ 6 feet plus
 (Bottom of clay not exposed.)

 A grayish-green jointed clay has been used in the manufacture of common brick in two localities in the vicinity of Lake City.
 At Campville, in Alachua County, a clay which is probably of Alum Bluff age is now being used for a good grade of common brick. A section of this deposit is:
 Soil and sand ............................................... 3 feet
 W hite sandy clay ............................................. 7 feet
 Red and gray spotted clay..................................... 16 feet
 Red sandy clay .............................................. ?

 Green and grayish Alum Bluff clays are exposed in Hatchett Creek one mile northeast of Fairbanks. Phosphatic clays, greenish to gray, are also found near Riverview in Hillsborough County and along the Gulf coast north of Dunedin in Pinellas County. This latter area probably represents an isolated remnant of the Alum Bluff.
 There is throughout much of the Alum Bluff region a superficial deposit of red sand and clay. This material consists of coarse quartz, sand, at times gravel, with a variable clay content which is often high. Small flakes of mica are also often present in large quantities. This material is extensively used for road metal in Lake, Polk, Orange and Marion counties in the peninsula and also in Leon, Gadsden and several other counties in west Florida. These deposits are only tentatively included in the Alum Bluff. It is exceedingly doubtful if this material is Miocene. Some of it is probably a residual mantle resulting from the weathering of Alum Bluff formations as well as other sediments. While much of it may have originally been Alum Bluff deposits it has been largely reworked by subsequent streams and currents. Its age may be regarded as still unsettled.
 It is doubtful if any clays representing the Jacksonville formation are exposed. The clays of Black Creek below Middleburg and those underlying South Jacksonville may be of Jacksonville age, but it seems more likely that they are of recent deposition.
 The Choctawhatchee formation, Miocene, underlies a limited area in west Florida extending through Leon, Liberty, Calhoun, Washing-