Barnacle plates, one o£ the most common constituents of Fort Pierce grid 

 cores, are uncommon in the Miami-Boca Raton shelf sediments. It is in- 

 teresting to note that De Palma (1969) found large quantities of barnacles 

 on test panels off Fort Lauderdale. Their scarcity in CERC sediment 

 samples from the Palm Beach-Miami area may be a result of the inability 

 of the barnacles to successfully compete with other organisms living on 

 the natural substrata. 



North of Boca Raton, the inner part of the shelf is covered by a 

 blanket of homogeneous fine gray quartzose sand. The outer part of the 

 shelf has not been sampled by cores, but is believed to contain material 

 similar to shelf sediments south of Boca Raton. 



Except for some similarity of Type D sediment at Fort Pierce grid 

 to the well sorted gray sands between Palm Beach and Boca Raton, there is 

 no evidence in sediment constituents of significant interchange between 

 these regions. The similarity between Type D sand and the southern gray 

 sands is largely in coloration and sorting. The chief dissimilarity is 

 in the larger grain size of the material at Fort Pierce and the higher 

 quartz content of the sand found south of Palm Beach. While the gray 

 sand occurring off Palm Beach could be the product of southward transport- 

 ation of Type D material (with concomitant downdrift reduction in size 

 and carbonkte content) , it does not seem possible that the gray sands off 

 Palm Beach could have been the source of Type D material. 



Another possible source of sediment for Fort Pierce grid is on the 

 shelf to the north. Cores from Cape Kennedy are now under study for a 

 forthcoming ICONS report, but only preliminary analysis is available. 

 These analyses show that sand similar to that found at Fort Pierce is 

 present at Cape Kennedy; however, much dissimilar material is also present. 

 On the whole. Cape Kennedy sediments are more quartzose than those at Fort 

 Pierce and cores from the Fort Pierce-Cape Kennedy reconnaissance lines 

 do not contain material which obviously indicates transfer of sediments 

 within the depth range sampled (40 to 55 feet) . 



If material is being brought down presently from the Cape Kennedy 

 shelf to Fort Pierce grid it must be transported outside the area covered 

 by. cores. It is significant that the shelf between Cape Kennedy and Fort 

 Pierce is slightly deeper and generally free of the topograhic irregular- 

 ities which would be expected if shoals were migrating southward from 

 the Cape Kennedy area (Figure 5) . Also if any large quantities of sand 

 were moving, either in waves or by sheet flow, southward from Cape Kennedy, 

 one would expect that infilling of the deeper embayed section of the shelf 

 off Canaveral Bight by sandy sediment would occur before much material was 

 transported further southward. Fine sediments (silt and clay) ponded in 

 Canaveral Bight are evidence that sand is not now being bypassed through 

 this area either from north or south. 



Material may have been exchanged between the Cape Kennedy and Fort 

 Pierce areas at a past time of lowered sea level, but firm evidence of 

 continuity or direct relationship requires additional sediment samples 



48 



