The reconnaissance line extending from Jacksonville to St. Augustine is characterized by 

 relatively tiiick sequences (greater than 8 feet) of type A sand. Of the 18 cores from this 

 section, 12 contain type A sand to the bottom. Only sediment types A and F are in this 

 region, and their occurrence is correlative between cores. Older strata occur at or near the 

 surface at several locations in the St. Augustine grid. These deposits include type L and only 

 rarely type M, both of which are more common at Jacksonville and north; and several 

 lithologies whicti are referred to either as type G or unclassified sediment (U). The 

 unclassified sediments represent many diverse lithologies while type G sediment is typically 

 coarse quartzose-moUuskan sands, judged to be Pleistocene in age. Core 129 on Une J in 

 Figure 34 shows a thin, poorly indurated calcarenite overlying Tertiary deposits. 



(3) St. Augustine to Cape Canaveral. Sediment character changes south of 

 St. Augustine as the surface Quaternary sediments thicken and display facies changes that 

 are quite marked on shore-normal lines but not clearly defined on shore -parallel lines 

 (Figs. 35 and 36). Clayey silt deposits and muddy shell gravels, not present north of 

 St. Augustine, occur nearshore in surface and subsurface units along the reconnaissance Une, 

 particularly south of Daytona Beach. Most muds and shell gravels are adjacent to the 

 Mosquito Lagoon barrier and may simply reflect a migration of the lagoon-barrier island 

 complex landward during the last rise in sea level. The relation between selected cores along 

 the reconnaissance line is shown in Figure 35. Along line A— A^ the southernmost 

 near-surface occurrence of Tertiary strata is in core 142. Overlying sediments are very fine 

 to fine silty sands of uncertain origin. Cores not alined in shore-parallel configuration show 

 onshore-offshore facies changes. Nearshore cores at C\ B', and E' (Fig. 36) contain buried 

 sands and (bioturbated) muds with deeply weathered shells. These deposits pinch out 

 seaward beneatli the surface deposits of clean medium quartz sand. Profile F-F^ is a 

 simplified example of the same trend; shelf sands are replaced landward by older, lagoonal 

 deposits. 



Trends in sediment thickness and character along the reconnaissance hne, particularly 

 south of Daytona, are hnear shore-parallel patterns different from those north of 

 St. Augustine. Tlie patterns are similar to those mapped by Field and Duane (1974) in the 

 Cape Canaveral area. 



IV. DISCUSSION 

 1. Shallow Subbottom Stratigraphy and Structure. 



Although stratigraphically logged wells from the coastal zone of northeastern Florida are 

 scarce, a sufficient number exists for tentative correlation between onshore coastal geology 

 and reflection units beneath tlie inner Continental Shelf (Table 4). Of the five reflection 

 units observed in this study, all but the red unit probably extend under the east Florida 

 landmass where they should be represented in coastal wells. 



67 



