578 GINSBUKG, LLOYD, STOCKMAN AND MCCALLUM [CHAP. 22 



At present, these data are not available. Should they be assembled, they might 

 provide critical information on the relative contribution of algae. 



Lo^\'enstam and Epstein's study of the isotope ratios of sediment and algal 

 needles from several areas on Great Bahama Bank provides additional evidence 

 that the aragonite needles in the sediment are derived from fragile green algae 

 {op. cit.). These authors found that the oxygen isotope ratios of the sediment 

 needles fall \\ithin the range of values determined for the needles in green algae 

 living in the area where the needle-bearing muds are found {op. cit., p. 372). 



7. Distribution of Non-skeletal Particles 



All of the available information on the occurrence and distribution of non- 

 skeletal particles has been obtained from studies in the Florida-Bahama-Cuba 

 region. The studies of Illing, Daetwyler and Kidwell, Newell and his associates, 

 Purdy, and the present authors have shown that non-skeletal particles are 

 abundant — often even the dominant constituent of the sediments — and that 

 their areas of maximum abundance show distinct relationships to the water 

 circulation. Moreover, the distribution of the two tjq^es of particles appears to 

 bear some relationship to smaller variations in the circulation of water. 



llling's samples from the southeastern Bahamas showed that the sediments 

 of the marginal zone are skeletal and that those of the interior of the Bank are 

 non-skeletal (Table III). More recently, an extensive study of the sediments on 



Table III 



Constituent Composition of the Surface Sediments on Great Bahama Bank 



(from Illing, 1954, p. 17) 



the northwestern Bank by Purdy has shown that non-skeletal sediments 

 predominate on the Bank outside the area of lime mud (Fig. 14). Together, 

 these studies indicate that non-skeletal sands are volumetrically the most 

 abundant sediment on Great Bahama Bank, and that over the large interior 

 they form 70% or more of the total sediment. Daetwyler and Kidwell have 



