I)KKI SKA DKPOSITS 



The slow accumulation of sediment on the deep-sea bottom, the 

 aWnce of transportation there, and the nature and small size of 

 the particles, all favor chemical reactions which result in the forma- 

 tion of many new products, such as glauconite, phosphatic and man- 

 ganic nodules, zeolites, 1 etc. The amount of matter arising from the x 

 decomposition and alteration of minerals and rocks increases, rela- 

 tively, with increase of distance from the land. At the same time 

 tlu-re is an increase (relative), in all moderate depths, of the remains 

 of pelagic organisms. We thus pass insensibly from deep-sea 

 deposits of a terrestrial origin (terrigenous deposits) near the land, 

 to pelagic deposits, ' ' in which the remains of calcareous and siliceous 

 organisms, clays, and other substances of secondary origin play the 

 principal role." 2 



The following table 3 shows the relations of the various groups 

 of marine deposits. 



Deep-sea deposits beyond 



100 fathoms. . 



Red clay 

 Radiolarian ooze 

 Diatom ooze 

 Globigerina ooze 

 Pteropod ooze 

 Blue mud 

 Red mud 

 Green mud 

 Volcanic mud 

 Coral mud 



deposits f .. 



, I Sands, gravels, 



Shallow-water 



between low-water mark 



and 100 fathoms.. . 1 muds ' etc " 



3. Littoral deposits between 

 high- and low-water marks 



\ Sands, gravels, 



muds, etc. 



Pelagic deposits 



formed in deep 

 water far removed 

 from land 



II. Terrigenous depos- 

 its formed in deep 

 and shallow water, 

 mostly close to 

 land 



In spite of this classification of Murray, the coral and volcanic 

 muds cannot be regarded as terrigenous, and shells, coral, etc., are 

 found abundantly in shallow-water deposits. It is to be noted 

 that the pelagic deposits are partly organic and partly inorganic 

 in origin. The latter may be of mechanical or chemical origin. 



Mechanical inorganic deposits. The mechanical deposits of the 

 deep sea come from (i) the land by the ordinary processes of grada- 

 tion, (2) volcanic vents, and (3) extra-terrestrial sources. The 

 terrigenous materials which reach the deep sea are, as a rule, only 



1 " The generic name for a group of hydrated double silicates in which the 



Ie principal bases are aluminum, and calcium or sodium." 

 - Murray, Challenger Rept., Deep Sea Deposits. 

 3 Ibid., p. 186. 



