classified above. Type Ul sediment is found in a few cores j but only 

 from the shoreface area. The high quartzose content suggests this ma- 

 terial may be largely derived from quartz-rich deposits on the present 

 beach . 



The source of most sediment particles found in Fort Pierce grid 

 cores is the benthic biota. Organisms contributing to the material - 

 insofar as can be determined - are indigenous to the area. Quartz, the 

 only noncarbonate element present in significant quantity, must have" 

 been derived from the Piedmont Province since no primary quartz-bearing 

 rocks crop out on the Florida Peninsula (Puri and Vernon, 1964 and Pilkey, 

 et al. (1969). Net drift of sediment on the east Florida coast is south- 

 ward (Watts, 1953; Giles and Pilkey, 1965; Bruun, Geritsen and Morgan, 

 1958). Studies of the southern Atlantic Shelf indicate that shelf sedi- 

 ment transport parallel to shore may not be an important process (Pilkey, 

 1968 and 1969). Thus, movement, if any, is probably in a general onshore- 

 offshore direction. 



The dominant carbonate suite may have been created in recent times 

 by organisms inhabiting the area of accumulation or may have originated 

 outside the grid area and subsequently entered as detrital sediments. 

 A third possibility is that the skeletal fragments were reworked from 

 older underlying formations. Available information indicates all three 

 processes probably played a part in sedimentation of the inner shelf area, 

 and through time the dominant depositional process may have differed for 

 different sediment types. 



The deepest, and presumably oldest, stratum reached by Fort Pierce 

 cores is the stratum containing Type E material. The top of this stratum 

 is tentatively correlated with the blue acoustic reflector (Figures 7, 8, 

 and 9) . It is believed that the E stratum was deposited during or prior 

 to the late Wisconsin regression commencing some 30,000 years Before 

 Present. One evidence of this minimum age is that indurated layers occur 

 within the Type E stratum. Induration of clastic carbonate sediments 

 strongly - but not conclusively - indicates exposure to subaerial or 

 littoral conditions (Ginsburg, 1957; Friedman, 1964), therefore suggesting 

 exposure during the late Wisconsin regression or earlier. A further in- 

 dication is that projected depths of the blue reflector under the coastal 

 ridge are equal to or below the top of the Anastasia formation in the 

 coastal region; Anastasia rocks are presumably Sangamonian (last 

 interglacial) and possibly earlier in age (Cooke, 1945; Puri and Vernon, 

 1964). 



Type E material from the outer shelf does not resemble descriptions 

 given to Anastasia rocks in the coastal area. However, the Anastasia is 

 lithologically variable and little is known concerning its character - or 

 existence - seaward of the coastline. Two cores from the inner shelf area, 

 45A and 34, contained plugs of rock in the cutter head which resemble rocks 

 presumed Anastasia found near the shore at Fort Pierce. Elsewhere the 

 Type E material of the inner shelf is not inconsistent with the wide- 

 ranging lithologic description of the Anastasia Formation in coastal 

 Florida, 



45 



