structure underlying northeastern Florida. Under the Georgia Atlantic Coastal Plain the axis 

 of the embayment trends southeastward. It has been traced offshore under the Atlantic 

 shelf by Antoine and Henry (1965). 



The second significant structural feature is the Sanford High (Vernon, 1951). Vernon 

 described this feature as a half dome truncated by a fault bounding the eastern border of the 

 Kissimmee faulted flexure. 



Because of their proximity to the surface, only rocks of late Eocene age and younger are 

 pertinent to this study; these rocks include limestone of Eocene and Miocene age and clastic 

 sediments of Miocene through Holocene age (Table 1). An important nonstratigraphic unit 

 witliin these strata is the Floridan aquifer (Parker, 1951) which locally cuts across 

 stratigraphic boundaries. In the main the aquifer is associated with hmestones of Eocene and 

 Oligocene age but includes permeable units in the lower Miocene section as well. The 

 aquiclude consists of impermeable strata in the Miocene section; consequently in most 

 places the Miocene and pre-Miocene contact is the upper boundary of the aquifer. 



b. Eocene Strata. All upper Eocene strata underlying Florida have been designated tlie 

 Ocala Group by Puri (1953a). The group includes three Hthologically similar hmestone 

 formations. In ascending order these formations are the Ingles, Williston, and Crystal River. 

 In coastal areas where data on these formations must be based on well samples the three are 

 often undifferentiated in well logs. The Ocala Group overlies the eroded surface of the 

 middle Eocene Avon Park limestone. The lowermost formation, the Ingles, consists of 

 cream-colored to white fossiliferous marine limestone. The overlying Williston Formation is 

 similar to the Ingles. Puri and Vernon (1964) describe the uppermost Crystal River 

 Formation as a microcoquina made up almost entirely of foraminifera tests; however, the 

 basal section may contain beds of secondary dolomite. The surface of the Crystal River 

 Formation lias been subject to post-Eocene erosion, and in Volusia County and northern 

 Brevard County it is reported that the formation has probably been removed (Wyrick, 1960; 

 Brown, et al., 1962). 



c. Post-Eocene Strata. Miocene stratigraphy of Florida is best known in the panhandle 

 region and in the central and western parts of the Florida peninsula where outcrops and 

 shallow subcrops are accessible for study. Within study limits only reports from Brevard, 

 Duval, and Nassau Counties provide a breakdown of sediments of Miocene and PHocene age. 

 In these tliree counties, wliich underlie the north and south ends of the study area, the basal 

 Miocene unit is identified as the Hawtliorn Formation of Miocene age (Leve, 1961a, b; 

 Brown, et al., 1962). This formation is found lying directly on tiie eroded surface of Eocene 

 rocks and is in turn overlain by undifferentiated beds of upper Miocene and Pliocene age. 



In Volusia and St. Johns Counties— and presumably Flagler County in between— the 

 Hawthorn Formation is apparently absent and sediments of upper Miocene and Phocene age 

 directly overlie the Eocene surface (Tarver, 1958; Bermes, 1958; Wyrick, 1960). 



17 



