Ridges are generally barren or contain only isolated, thin sediment 

 patches. Other areas of Figure 16 indicating sediment accumulation 

 represent the position of swales on plateaus vvhere sediment accumulation 

 of 2 or 3 feet occurs. Topographic highs which terminate the plateaus 

 are generally barren of sediment, or contain only thin and areally small 

 accuT-ulations . 



A large volume of sediment apparently does exist in the shoreface 

 terrace because some borings have penetrated sediment sections 15 to 18 

 feet thick. Shallow waters and wave action precluded obtaining cores or 

 seismic profiles; consequently no direct correlations of data from this 

 area can be made with data obtained in the Miami grid. 



e. Coastal Morphology and Sediment Characteristics 



Between Government Cut at Miami and Lake Worth Inlet near 

 Palm Beach the southeast Florida coastline extends in an almost straight 

 line, bearing about 6° east from a north-south direction. It is a 

 "barrier coast" in the coastal classification of Shepard (1963). The 

 irnnediate coastal area lies along sandy barrier islands and spits backed 

 by bays, lagoons, marshes and improved sections of the Intracoastal 

 Watenvay. Tne highly developed coastal zone is broken by seven inlets, 

 and protected by numerous groins and almost 20 miles (29 percent) of 

 seawalls and bulkheads. Most of these shoreline improvements are concen- 

 trated in the southern half of the area. Physical characteristics of the 

 beach vary because it is influenced and localized by the numerous engi- 

 neering structures and inlets. Figure 17 is a graphic plot of the median 

 dianeter of beach samples compiled from various sources. The wide range 

 of median size between relatively closely spaced stations and the lack of 

 agreement between data from different sources do not favor generalization. 



The acid-soluble content of beach samples from the study area ranges 

 fro3 45 to 85 percent. Visual examination shows that the acid- soluble 

 content is almost entirely of biologic origin with mollusk fragments the 

 rost significant constituent. These fragments are generally tabular, 

 sturdy, and well rounded; many have a high polish. 



Occasional exposures of coquina rock appear along the beach. Numerous 

 borings and probings in the waterways behind the beach encountered rock 

 identified as limestone or coquina at less than -15 feet MLW; most prob- 

 ably the .Anastasia Formation or its facies equivalent. Offshore the rocky- 

 surface of the inner flat generally commences at less than -15 feet water 

 depth suggesting that the rock is continuous under' the beach zone. 



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