RED CLAY 217 



proportion of amorphous clayey matter, usually of a 

 reddish colour, passing in some regions into a dark 

 chocolate colour from the abundance of small grains of 

 peroxide of manganese. Usually the Red Clay contains 

 very few, if any, remains of calcareous organisms, but 

 occasionally there may be an appreciable admixture 

 of the shells of pelagic and bottom-living Foraminifera, 

 teeth and otoliths of fishes, fragments of Echinoderms, 

 Molluscs, Ostracods, Polyzoa, etc., and on approaching 

 shallower water in tropical and temperate regions, the 

 shells of pelagic Foraminifera become more and more 

 numerous until the Red Clay passes into Globigerina 

 Ooze. The remains of siliceous organisms (Radiolaria, 

 Diatoms, Sponge spicules, arenaceous Foraminifera) 

 may generally be detected ; and in some regions where 

 the Radiolarian remains become abundant, the Red 

 Clay passes gradually into Radiolarian Ooze, while in 

 other regions towards the far north and far south the 

 Diatom remains increase in number, and the Red 

 Clay may pass into Diatom Ooze. Among the in- 

 organic elements met with in Red Clay, the most con- 

 stant and widely distributed is pumice, which occurs 

 in larger and smaller fragments down to the most 

 minute particles, and in all stages of disintegration and 

 decomposition ; the minerals found in pumice, like 

 sanidine, plagioclase, augite, hornblende, magnetite, 

 etc., are also present, along with basic volcanic glasses 

 frequently transformed into palagonite. The peroxides 

 of iron and manganese are universally distributed 

 throughout the Red Clay, sometimes as minute grains 

 or coatings, sometimes deposited as concretions around 

 organic remains, pumice fragments, and other nuclei, 

 forming manganese nodules of larger or smaller size, 

 especially where the debris, ashes, and lapilli, of basic 

 volcanic rocks are abundant and have undergone 



