Table 4. Stratigraphic summary of reflection units. 



Reflection unit 



Sediment 



Probable age 



A 



sand, silt, clay, shells 



Pliocene-Pleistocene, Holocene 



B 



sand, silt 



late Miocene 



C 



clay, sand 



Miocene 



D 



clay, sand 



Miocene 



E 



limestone 



Eocene, Oligocene, Miocene 



Between Cape Canaveral and Palm Valley (30°10'N.) the green primary reflector 

 correlates closely with elevations in coastal wells on top of the Floridan artesian aquifer 

 (Bermes, 1958; Tarver, 1958; Wyrick, 1960; Brown, et al., 1962). The top of this aquifer is 

 common but not everywhere coincident with the top of the Eocene section. 



North of Palm Valley, wells at Jacksonville Beach and Fernandina Beach (Leve, 

 1961a, b) show the top of the Floridan aquifer lying over 500 feet below mean sea level 

 (MSL) while the green reflector lies under the adjacent shelf no more than 350 feet below 

 MSL (Fig. 15). Reasons for this are not clear; possibly the green surface actually dips 

 northward to over 500 feet below sea level at Jacksonville, but is obscured by an 

 overlapping strong reflector which may appear on seismic reflection records as a direct 

 continuation of the green surface. Alternatively there may be a sharp downward 

 displacement of the green unit between the inshore boundary of the survey area and the 

 onshore wells at Jacksonville and Fernandina. 



Faults and solution features occur in Eocene strata underlying the Florida peninsula and 

 it is hkely that similar features occur in the green unit; however, there is no clear evidence of 

 either in the seismic reflection profiles. Some small angular irregularities of the green 

 reflectors may result from fault displacement rather than erosion but firm evidence is 

 lacking. If large solution features do exist it is probable that they are either masked by tlie 

 generally poor reflection returns from below the green reflector or by insufficient acoustic 

 contrast at the boundaries. 



The purple reflection unit and the overlying white unit lie at elevations similar to those 

 of coastal wells in units comprising the aquiclude of the Floridan aquifer. These strata are 

 relatively impermeable, and in the coastal zone are generally considered to consist of 

 Miocene beds. 



Over tlie structural liigh off Daytona Beach the purple and white units and tlie overlying 

 red unit are missing or too thin to be resolved on available seismic reflection records. The 

 Floridan aquifer tlius appears to be breached in this locale as the overlying sediments of the 

 blue reflection unit consist generally of permeable elastics. 



The red reflection unit is beUeved to be confined primarily to the shelf area and not 

 continuous witii any widespread deposit under the adjacent landmass. Since this unit is 



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