Waterway. The mainland shore is bordered by a flat-topped coastal ridge 

 which rarely exceeds 30 feet in elevation and 5 miles in width. Inland 

 of the coastal ridge is an extensive, low plain, characterized by its 

 numerous lakes, sinks, streams and swamps. 



b. Stratigraphy and Geologic History 



(1) General. An extremely thick section of sedimentary rocks 

 underlies the study area; however, only the uppermost strata are germane 

 to this report (Table I) . Consequently the following discussion is 

 limited to the upper Eocene Ocala Group (Puri, 1953) and younger rocks. 

 (For a general discussion of older strata, see Cooke, 1945, and Puri and 

 Vernon, 1964.) Knowledge of lithology, structure and formational bound- 

 aries of pre-Pleistocene rocks in the coastal area is scant. Existing 

 knowledge is based largely on scattered well logs and projection from 

 outcrops situated some distance inland. 



(2) Eocene and Oligocene Strata . The Eocene Ocala Group as de- 

 fined by Puri (1953) includes in ascending order the Ingles, Williston, 

 and Crystal River Formations - all lithologically similar. Rocks of the 

 Ocala Group are characteristically white- or cream- colored, granular lime- 

 stones described in well logs as varying from soft to hard, and containing 

 abundant fossils. At Cape Kennedy, the top of the Ocala Group lies at 

 -180 feet MLW (Brown, et al . , 1962). From Cape Kennedy, the top of the 

 Ocala Group dips southward and eastward to -380 feet MLW near the Brevard- 

 Indian River County line. Well logs from Indian River and Martin Counties 

 indicate a sharp drop in the Ocala surface near the shoreline. On the 

 basis of these well logs and other evidence, the sharp dip is attributed to 

 a fault or series of faults trending more or less parallel to the present 

 shoreline. The fault presumably is continuous through St. Lucie County. 

 There is no clear evidence that the coastal fault extends north into 

 Brevard County, although farther west a fault with similar strike is known 

 (Brown, et al., 1962). A sharp increase in the dip of the Ocala occurring 

 near the south line of Brevard County may indicate that the hinge line of 

 this fault lies in this location. Further evidence of a sharp southward 

 dip, in a presumed upper Eocene-Ocala surface commencing south of Cape 

 Kennedy, occurs on seismic reflection records made in the Florida ICONS 

 Program (Meisburger and Duane, 1969). 



Oligocene rocks have not been reported from Brevard County. Rocks of 

 Oligocene age lie unconformably on the eroded Ocala Group in the southern 

 part of the study area (Indian River, St. Lucie and Martin Counties). 

 Variously described as gray limestone with calcite crystals and soft 

 granular limestone, the strata are thickest on the downthrown block east 

 of the coastal fault zone and south of the Brevard County line (Bermes, 

 1958; Lichtler, 1960) . 



The Eocene and (where present) the Oligocene rocks of east Florida 

 form the upper layers of the permeable Florida artesian aquifer. Imper- 

 meable units in the overlying Miocene section form the aquiclude. Some 



