Bajst'd on ostracod species and abundance of planktonic foraminifera it is estimated that 

 the original eiu'ironment of deposition for most type L sediment was 200 feet deep, or 

 about 120 feet deeper than at present. Onshore marine terraces occur as high as 120 feet 

 (Penholoway Terrace) and the upper two terraces have been assigned a Pliocene age (Alt and 

 Brooks, 1965). This information corroborates, in a general way, a deepwater environment of 

 about 300 feet for a relatively short duration during which time type L sands were 

 deposited. 



b. Significance of Mud and Shell Gravels. Sediments with modal sizes larger or smaller 

 than sand (0.63 to 2.0 milUmeters; 4.0 to —1.0 phi) are rare on the north Florida inner 

 shelf. In a shallow stratigraphic record of a transgressed shelf, sediments of all sizes are 

 usually present, reflecting the preservation, at least in part, of the highly variable 

 environments. At Cape Canaveral, lagoonal deposits are common in surface and near -surface 

 deposits (Field and Duane, 1974). Adjacent to the barrier island coasts of the middle 

 Atlantic Bight, estuarine and lagoonal facies are commonly present beneath the shelf surface 

 (Duane, et al., 1972; Shideler, et al., 1972; Swift, et al., 1972). In both areas, deposits are 

 typically composed of sandy and clayey silts with occasional channel clays, and admixtures 

 of shell gravel with silt. Peat deposits and organic muds are often present. 



The near absence of shallow subsurface muds and shell gravels on the north Florida inner 

 shelf indicates eitiier complete removal of that section of the stratigraphic record or absence 

 of a significant barrier coast during Holocene development. Since extensive removal of back 

 barrier facies has not occurred elsewhere, the latter explanation seems more accurate. 

 Although silt to fine grain deposits and muddy shell gravels occur at St. Augustine and 

 north, their distribution and extent are very hmited. Along the reconnaissance Une south of 

 St. Augustine these particular lithologies become more abundant. This section of the survey 

 area has a well defined barrier4agoon configuration (Fig. 35). Mosquito Lagoon is over 26 

 nautical miles long, approximately 3.5 nautical miles wide and is separated from the 

 ocean by a narrow 0.5 nautical mile barrier. The occurrence of lagoonal sediments (poorly 

 sorted shell gravels and muds bearing lagoonal fauna) at shallow sediment depths on the 

 inner shelf suggests that a barrier analogous to the present one existed during early Holocene 

 at a point seaward of the existing slioreline. Interpretation of the large shoals off Cape 

 Canaveral as remnants of a relict cuspate foreland by Field and Duane (1974) provides 

 supporting information for existence of a barrier-beach ridge complex at this end of the 

 survey region. 



c. Generation of Surficial Quartzose Deposits. 



(1) Quaternary Fluvial Sources. The dominance of quartz sand in surface and 

 near-surface deposits throughout the study area has been emphasized in this report. Based 

 on earlier works (Gorshne, 1963; Pilkey, 1963; Giles and Pilkey, 1965; MiUiman, 1972) the 

 quartz sands of the shelf (Types A and F) and the beach sands have characteristics which 

 indicate an ultimate derivation from the Georgia Piedmont province. These ciiaracteristics 



74 



