make up 50% of the clasts in beachrock on the present shore but 

 less than 20% of the clasts in the submerged beachrock. The 

 clast size in each deposit ranges from sand to cobbles and boulders 

 as large as 4 feet in greatest dimension. The size of the clasts 

 in the submerged beachrock decrease toward the top of the deposit 

 and generally toward the seaward edge . Both contemporary and 

 submerged beachrock contain parallel graded beds inclined as much 

 as 12 degrees seaward. 



RELICT SEA LEVEL AT 43 +3 FEET 



The submerged beachrock at Cabritte Horn Point (figure 2) is more 

 than 300 feet long, 90 feet wide, and reaches a maximum of 5 feet 

 in thickness. Channels through the beachrock expose bedrock sub- 

 strate on which the beachrock rests. The beachrock is eroded and 

 undercut as much as 10 feet along the beachrock-bedrock contact . 

 Corals, alcyonarians, and hydrozoans grow in isolated colonies on 

 the beachrock surface and coalesce to partly cover the seaward 

 part of the deposit. A cobble-boulder gravel (fig. 2, profile 1) 

 partly covers the landward edge. The contact between the beachrock 

 and the cobble-boulder gravel defines a change in slope, for the 

 surface of the gravel is more steeply inclined seaward. The 

 cobble-boulder gravel consists of well-rounded carbonate and 

 noncarbonate clasts, similar in size and composition to those in 

 the beachrock and partly encrusted by calcareous algae, coral, and 

 hydrozoans. Cobble and boulder gravel occur landward from beach- 

 rock on the present beaches in Greater Lameshur Bay, Grootpan Bay, 

 Kittle Bay, and Salt Pond Bay. As in the submerged deposits, the 

 gravel surface slopes seaward more steeply than the beachrock 

 surface. 



Beachrock occurs on the southwest side of Cabritte Horn Point as 

 small patches of indurated conglomerate at the landward edge of 

 an erosional bedrock platform (figure 2) . Most of the deposits 

 are thin and rest on bedrock; coral covers their seaward surfaces. 

 Where beachrock is absent , uncemented cobbles and boulders occur 

 at the landward edge of the platform. Seaward of the platform, 

 a veneer of coral growth forms a reef that covers the bedrock 

 surface. From the coral reef, a broad plain, floored by carbonate 

 sand, extends seaward. Except for a narrow unvegetated strip 

 adjacent to the reef, the plain is vegetated by the calcareous 

 algal flora Halimeda , Udotea , and Pennicilus . 



On the algal plain, concentrations of well-rounded noncarbonate 

 cobbles and boulders exist locally (figure 2) at depths of 40 to 

 45 feet and 62 to 73 feet. Most of the clasts are less than one 

 foot in diameter, but rounded clasts up to 3 feet long are found 

 at depths of 72 feet (figure 2, station 1 and 2). These non- 

 carbonate clasts may have been deposited when the sea level was 

 considerably lower than its present level; their emplacement under 

 present conditions seems unlikely. 



The substrate on the algal plain northwest of Cabritte Horn Point 

 at a depth of 48 feet was investigated to a depth of 34 inches. 



VI-73 



