(3) Unit C. Unit C is 90 feet thick near the Georgia border but thins rapidly toward 

 the south and pinches out between Jacksonville and St. Augustine. This unit is cliaracterized 

 by internal reflectors suggesting a series of foreset-type beds followed by stretches of 

 bottomset-type beds overlain by gently dipping subparaUel beds. In contrast to the overlying 

 unit B where internal reflectors dip almost due east, internal reflectors in unit C tend to tip 

 in a southeasterly direction. 



(4) Unit D. Unit D is not well defined in the northern part of the study area because 

 it generally hes in a zone of strong multiples. As the unit rises southward its boundaries and 

 internal reflector pattern become clearer. The internal reflectors, where clearly visible near 

 St. Augustine, are weak but definite, closely spaced and mutually parallel. The internal 

 reflectors dip generally in the same direction as the unit as a wliole whicli ranges from north 

 to southeast. Over the high at Daytona Beach the unit appears to have been entirely 

 removed by erosion. 



(5) Unit E. Unit E includes all strata below the green reflector and within penetration 

 range of the records. Internal reflectors within unit E are scarce and discontinuous; there is 

 very little information available concerning its possible structural and bedding 

 characteristics. 



(6) Unit F. Unit F includes all strata between the green and red reflectors south of 

 the Daytona Beach high (Fig. 14). Tliis unit is cliaracterized by regular seaward-dipping 

 internal reflectors. Offshore the unit thickens rapidly eastward and reaches a thickness of 

 over 300 feet within 5 nautical miles of Cape Canaveral. No direct connection of this unit 

 with any of the intermediate units (B, C, or D) north of the Daytona High has been 

 establislied; however, unit F is most Ukely a time equivalent of one or more of these units, 

 and its internal reflectors suggest a progradational bedding and stratigraphic position similar 

 to unit B. 



d. Primary Reflectors. The uppermost reflector in the blue unit which is traceable over 

 a large part of the grid areas was selected to serve as a basis for sediment thickness maps of 

 the three gridded areas. By convention the isopach surface in ICONS studies is called the 

 blue reflector. This does not imply that the blue reflector of this study is necessarily 

 continuous with blue reflectors described in other ICONS studies. It is not known if 

 continuity exists between grid areas, although core data and similarities in elevation indicate 

 a probability. 



The blue reflector probably represents an eroded surface. In the inner parts 6f tlie 

 Jacksonville and Fernandina grids where the red unit is high, the blue reflector is coincident 

 with the top of the unit and truncates internal reflectors within the unit. Elsewhere up to 20 

 feet of sediment separate the blue reflector and tlie top of the red unit. 



The blue reflector dips eastward at a very gentle gradient nearly parallel to the shelf 

 floor; it often intersects offshore and becomes continuous witli the shelf floor. 



36 



