DEEP-SEA DEPOSITS 93 



posits, the siliceous remains are influenced by the sol- 

 vent action of the bottom water, aUhough to a lesser 

 extent. The silica set free as colloidal silica has a ten- 

 dency to migrate vertically and reappear as a cementa- 

 tion with autochthonous silica. Neither the radiolarian 

 nor the diatom skeletons lend themselves to such 

 climatological inferences as do the forams. 



Of considerable interest as an element of sediment 

 is humus-carbon, which, like nitrogen, serves as a 

 measure of the accruement of organic matter in the 

 deposit. It was long assumed that there is a linear 

 relationship between carbon and nitrogen, but the work 

 of Wiseman and Bennett ^ revealed that there are — 

 especially in deposits from the Arabian Sea — great 

 variations in the carbon-nitrogen ratio, so that nitrogen 

 cannot safely be taken as an adequate measure of the 

 organic matter. 



The phosphorus content in sediments is of con- 

 siderable importance, since phosphorous compounds 

 are essential to the flourishing of phytoplankton. Cor- 

 rens' study of material from the "Meteor" Expedition 

 proved that the phosphorus associated with calcium 

 carbonate, deposited as skeletons of planktonic or- 

 ganisms, is largely retained in the sediment if the car- 

 bonate is dissolved. Several investigators have pointed 

 out that sea water below the euphotic zone, where 

 phosphates are consumed by the phytoplankton, is 

 rich in phosphates. This makes the up welling of water 

 from the deep of ecological importance, since it acts as 



