FLORIDA GEOLOGICAL SURVEY


 TEXT TO ACCOMPANY
 THE GEOLOGIC MAP OF FLORIDA
 By
 Thomas M. Scott, P.G. 99

 INTRODUCTION
 The Florida Platform lies on the south-central part of the North American Plate,
extending to the southeast from the North American continent separating the Gulf of Mexico
from the Atlantic Ocean. The Florida Platform, as measured above the 300 foot (91 meter)
isobath, spans more than 350 miles (565 kilometers) at its greatest width and extends southward
more than 450 miles (725 kilometers) at its greatest length. The modern Florida peninsula is the
exposed part of the platform and lies predominantly east of the axis of the platform. Most of the
State of Florida lies on the Florida Platform; the western panhandle is part of the Gulf Coastal
Plain.
 The basement rocks of the Florida Platform include Precambrian-Cambrian igneous
rocks, Ordovician-Devonian sedimentary rocks, and Triassic-Jurassic volcanic rocks (Arthur,
1988). Florida's igneous and sedimentary foundation separated from what is now the African
Plate when the super-continent Pangea rifted apart in the Triassic (pre-Middle Jurassic?) and
sutured to the North American craton (Smith, 1982).
 A thick sequence of mid-Jurassic to Holocene sediments (unlithified to well lithified)
lies unconformably upon the eroded surface of the basement rocks. Carbonate sedimentation
predominated from mid-Jurassic until at least mid-Oligocene on most of the Florida Platform. In
response to renewed uplift and erosion in the Appalachian highlands to the north and sea-level
fluctuations, siliciclastic sediments began to encroach upon the carbonate-depositing
environments of the Florida Platform. Deposition of siliciclastic-bearing carbonates and
siliciclastic sediments predominated from mid-Oligocene to the Holocene over much of the
platform. Numerous disconformities that formed in response to nondeposition and erosion
resulting from sea-level fluctuations occur within the stratigraphic section.
 The oldest sediments exposed at the modem land surface are Middle Eocene carbonates
of the Avon Park Formation which crop out on the crest of the Ocala Platform in west-central
Florida. The pattern of exposures of younger sediments is obvious on the geologic map. Much
of the state is blanketed by Pliocene to Holocene siliciclastic and siliciclastic-bearing sediments
that were deposited in response to late Tertiary and Quaternary sea-level fluctuations.
 The characteristic landscape of Florida is relatively to extremely flat. There are few
large, natural exposures and limited smaller exposures that geologists can investigate. The result
is that geologists must rely primarily on de-watered or dry pits and quarries for exposures and
must make use of subsurface data in studying the geology of Florida. Subsurface data, in the
form of well cuttings and cores, were utilized extensively in the development of this map.
Formational tops recognized in the subsurface have been extrapolated to the surface where
exposures are limited.

 PREVIOUS INVESTIGATIONS
 Previously published geological maps of Florida include Smith (1881), Dall and Harris
(1892), Matson et al. (1909), Sellards, Gunter and Cooke (1922), Cooke and Mossom (1929),
Cooke (1945), Vernon (1951), Vernon and Puri (1964) and Brooks (1982).