114 FLORIDA GEOLOGICAL SURVEY— 15 TH ANNUAL REPORT 
Sandy soil . 2 feet 
Brown and gray sand with clay. 3 feet 
Gray clay. 3 inches 
White and green sandy clay. 3 feet 
Green 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 
White 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 prob¬ 
ably 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 in¬ 
cluded 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- 
