SECT. 3] SHALLOW-WATER CARBONATE SEDIMENTS 565 



to moUusks and Foraminifera, all the other skeletal types — corals, algae, 

 bryozoans, worms, alcyonarians and others. The reef-tract flora includes the 

 heavily calcified codiacean Halimeda (segments) and a variety of red algae 

 (crusts, sheaths, segments). These differences in the organic populations are 

 clearly reflected in the constituent composition of the sediments determined by 

 microscopic analysis of the fraction greater than |- mm, as shown in Table II 

 (Ginsburg, 1956, pp. 2424-2426). In addition to these very gross differences 



Table II 



Grain Size and Constituent Composition of Sediments from Florida Bay and the 



Reef Tract (from Ginsburg, 1956, p. 2399) 



on the phyletic level, differences on generic and specific levels occur in some 

 groups (see, for example, Moore, 1957, pp. 730-731). 



B. Great Bahama Bank 



The eastern side of Andros Island, Bahamas, shown in Fig. 7, has a physical 

 environment similar to that of the Florida reef tract (Newell, Rigby, Whiteman 

 and Bradley, 1951). As in Florida, the fauna and flora are varied and abundant. 

 The western side of Andros Island, on the other hand, is an area of restricted 

 water circulation similar to Florida Bay (Smith, 1940, pp. 158-164), and, like 

 Florida Bay, the fauna is dominated by mollusks and Foraminifera, and the 

 flora by lightly calcified green algae (sheaths) (Newell et al., 1959). 



Analysis of the constituent composition of some samj)les from each of these 

 areas by Thorp (1936, pp. 110-112) showed the same sort of contrast between 

 the two environments as was found in Florida (Fig. 7). 



