REPORT OF INVESTIGATIONS NO. 42


 OCALA GROUP

 The Ocala Group (Puri, 1957) includes three limestone
formations of late Eocene age. The subdivisions of the Ocala Group
(from youngest to oldest) are the Crystal River, the Williston,
and the Inglis Formations.

 CRYSTAL RIVER FORMATION

 The Crystal River Formation is primarily a coquina of large
foraminifers and crops out in an area extending from northern
Polk County through the southern end of Sumter County and into
eastern Hernando County. It ranges from 50 to 120 feet in
thickness, except in the eastern part of the area where it is absent.
In the central part of the area, the formation contains many
sand-filled cavities.

 WILLISTON FORMATION

 The Williston Formation is a tan-cream, medium to hard
limestone containing abundant micro-fossils. The formation is
slightly coarser than the underlying Inglis Formation but generally
finer than the overlying Crystal River Formation. In most of the
area, the Williston Formation ranges from 20 to 40 feet in thickness.
It is thin or absent along the eastern boundary of the area.

 INGLIS FORMATION

 The Inglis Formation is generally a white-tan, hard, fossil-
iferous limestone. The texture of the formation appears to be finer
than that of the Crystal River and Williston Formations. In most
of the area, the Inglis Formation is about 50 feet thick. It is thin
or absent along the eastern boundary of the Green Swamp area.

 AVON PARK LIMESTONE

 The Avon Park Limestone (Applin and Applin, 1944) of late
middle Eocene age was the deepest formation penetrated by test
drilling. The formation is nearest the surface on an upthrown
fault block along the eastern side of the area (fig. 8, A-A'). The
formation is found at considerable depth in the area south and
southwest of Green Swamp. The top of the formation is