SECT. 3] 



SHALLOW-WATER CARBONATE SEDIMENTS 



575 



^ i*. s:^ T ^*- 





1mm 



Fig. 13. 



A. Ooliths from Great Bahama Bank; thin sections, x 25. Top, plane light; bottom, 

 same area in polarized light. Simple and comjDound nuclei are shown. 



B. Fecal pellets from sediments west of Andros Island, x 25. Each of the pellets was 

 subjected to slight pressure from a needle. The different degrees of crushing reflect the 

 variable hardness of the pellets. 



C. Composite grains, "grapestone", from the sediments of the eastern Great Bahama 

 Bank, x 15. 



D. Thin section of the sample from which C was made, x 15, plane light. 



Illing's pioneer study of the marginal sediments of the southeastern Bahamas 

 suggested, as did Black's {op. cit.), that the slight warming of open ocean w^ater 

 as it flows up on the shallow Bahama Banks sets the stage for oolith formation. 

 Tiling believes that the increase in temperature produces the supersaturation of 

 carbonate necessary for precipitation, and that the movement of the bottom 



