60 



Shell Sand 



Description 



The shell sands are designated as those primarily com- 

 posed of shells or shell fragments with fine quartz-feldspar 

 sand as the host sediments Sands with abundant shell material 

 and associated authigenic minerals are excluded from this 

 typCo The organic remains, generally tests of Foraminif erat 

 are often broken « The roundness of the shells ranges from 

 .10 to o40, depending on whether or not they are broken, and 

 the sphericity ranges from „70 to .80. The accessory detrital 

 material is angular. 



Occurrence 



The shell sands are limited to patches occurring at the 

 outer ends of the submarine canyons. They represent the 

 accvimulation of shells as the coarse fraction of sediments 

 in offshore areas where the supply of coarse detrital material 

 is small. 



Phosphorite-Glauconite-Shell Sand 



Description 



The composition of this sand is extremely variable, but 

 the association of phosphorite, glauconite, and shell fragments 

 is so distinct that it warrants classification as a type. 

 Quartz, mica, and rock fragments occur in the sand as detrital 

 particles in minor amounts and the average heavy mineral con- 

 tent of the seind is 2.5%. The minimum percentage is 0.67o and 

 the maximum is 6.7%, as glauconite and phosphorite generally 



