CLASSIFICATION OF RECENT DEEP-SEA SEDIMENTS 



A. Carbonates and phosphates, mostly of calcium but 



with some magnesium 



1. Skeletons of marine organisms, either pelagic, 



such as Coccolithophoridae and certain fora- 

 minifera and moUusca, or benthonic and nerit- 

 ic, including corals, and certain calcareous 

 algae, moUusca, and foraminifera 



2. Inorganic calcium carbonate not formed directly 



by organisms 



B. Hydrated silica, usually as the test of radiolaria, 



frustules of diatoms, and skeletal fragments of 

 other organisms, but possibly also deposited in- 

 organically 

 ni. Authigenic substances. The products of submarine 

 weathering and diagenesis; including glauconite, 

 phillipsite, ferrous sulphide, iron manganese con- 

 cretions, probably certain clay minerals, and iron 

 and aluminium hydroxides, together with other 

 substances formed in place on the sea bottom 

 IV. Organic matter. The carlx)naceous and nitrogenous 

 remains of organisms (terrigenous in part) 



In any particular sediment, of course, a given com- 

 ponent may have originated in different ways. For ex- 

 ample, glauconite and calcium carbonate are often detri- 

 tal, whereas some ordinarily detrital minerals, such as 

 feldspar, occasionally may be authigenic. Furthermore, 

 the clay minerals and other products of subaerial weath- 

 ering may be indistinguishable from those possibly re- 

 sulting from submarine weathering. The colors of sedi- 

 ments largely depend on the colors of the constituents 

 listed under divisions I A, HI, and IV, although the pres- 

 ence of volcanic ejecta sometimes lends a dark color to 

 a deposit. 



Some sediments consist of only one or two of the 

 above groups of components and may be classified easily 

 according to the agents responsible for the origin of the 

 materials which they contain, as proposed by Grabau 

 (1904) and Holmes (1920). The majority of sediments, 

 however, contain many components, each of different or- 

 igin, and are accordingly difficult to classify on this ba- 

 sis. Furthermore, two sediments whose major compo- 

 nents are similar but which differ in their minor compo- 



nents may have been formed under quite different condi- 

 tions. Nevertheless, the conditions of formation are in 

 part reflected by the relative proportions of the compo- 

 nents and by the presence of certain constituents, so that 

 the mineralogical or modal composition of sediments is 

 of importance in classification. 



Previous Classification . The first attempt at clas- 

 sification of recent marine sediments was made by Mur- 

 ray and Renard (1884) primarily from the geographical 

 point of view although subdivisions were made accordirtg 

 to grain size, the preponderance of different groups of 

 organisms and different kinds of inorganic materials, 

 and color and calcium carbonate content. Murray and 

 Renard designate as deep-sea deposits all those beyond 

 the 100-fathom line and they divide these into two groups, 

 namely: terrigenous deposits formed in deep and shal- 

 low water close to land masses, and pelagic deposits 

 formed in deep water far removed from land, that is, in 

 the great central oceanic basins. Pelagic deposits, in 

 turn, are subdivided according to whether they consist 

 largely of the remains of organisms or of inorganic ma- 

 terials, the organic deposits being called oozes, and the 

 inorganic deposits being the red clay. The terrigenous 

 deep-sea deposits, called muds^ are subdivided on the 

 basis of color and physical composition. In outline, the 

 classification used by these authors is as given below. 



Subsequent authors, including Krummel (1907), 

 Andree (1920), and Johnstone (1923, following Herdman), 

 have modified in various ways the original grouping of 

 deep-sea sediments into pelagic and terrigenous depos- 

 its. All these writers, however, have retained essentially 

 the same deposit types as those proposed by Murray and 

 Renard. 



^Gripenberg (1934) has recently discussed the usage 

 of the term "mud ' which, she says, is analogous to the 

 term "gyttja" employed by limnologists, and should be 

 used to refer to the color and consistency of fine-grained 

 sediments regardless of their grain size. Typical muds 

 of the Baltic, for example, are loose and flocculent in 

 structure and black in color, as contrasted with clays of 

 the same region which are firm and gray. 



Classification of deposits 



Deep-sea deposits 

 (beyond 200-meter line) 



Shallow-water deposits 

 (between low water mark 

 and 200-meter line) 



Littoral deposits (on the 

 strand between high and 

 low water marks) 



Red clay 

 Radiolarian ooze 

 Diatom ooze 

 Giobigerina ooze 

 Pteropod ooze 



Blue mud 

 Red mud 

 Green mud 

 Volcanic mud 

 Coral sand and mud 



Gravel, sand, muds, etc. 



Stones, gravels, sands, 

 muds, etc. 



Pelagic deposits 

 (formed in deep water 

 far from lar-""* 



Terrigenous deposits 

 (formed in deep and 

 shallow-water close 

 to land masses) 



