CLASSIFICATION OF RECENT DEEP-SEA SEDIMENTS 



man (1903), Collet and Lee (1906), Clarke (1907), Joly 

 (1908), Caspar! (1910), Cushman (1910-1916), Clarke 

 and Steiger (1914), Odgn (1916), Heim (1924), Petter- 

 sson (1930), and others. They will be referred to in 

 connection with the later discussions of this paper. 



Likewise, no account has been given of those 

 expeditions and voyages on which deep-sea soundings 

 were made but bottom samples either were not 

 collected or not reported. For example, the Danish 

 ship Dana ( Dana Report no. 1, 1934 ), and the U.S.S. 



Ramapo ( see Hydrographic Office no. 210a and c, 

 1932, 1934 ) together with the U.S.S. Milwaukee and 

 other ships of the United States Navy, have carried 

 out extensive series of echo soundings in the south 

 and the north Pacific, which have added greatly to 

 our knowledge of the hydrography of the Pacific, and 

 therefore to our understanding of the relations be- 

 tween the various types of sediments on the bottom. 

 Owing to the method of soundings, however, no 

 bottom samples were collected. 



CLASSIFICATION OF RECENT DEEP-SEA SEDIMENTS 



Principles of Classification 



The purposes of a scientific classification of natu- 

 ral objects should be (1) to summarize the significance 

 of the similarities and differences between the objects 

 and to suggest ways in which their relations may be 

 studied; and (2) to systematize the nomenclature of the 

 objects through the setting up of an orderly series of 

 criteria or diagnostic characters by which they may be 

 distinguished from each other. A true classification 

 should be genetic, that is, the relations expressed by it 

 should be in terms of the origin and history of the ob- 

 jects classified. 



Since the conditions of formation and the origins of 

 the materials of deep-sea sediments are extremely com- 

 plex and often unknown or doubtful, it is desirable that 

 certain qualities of the sediments themselves, which 

 may be presumed to reflect their genesis, should be se- 

 lected as the basis of classification. Moreover, one of 

 the purposes of the study of deep-sea sediments is to 

 determine the significance of such factors as geographi- 

 cal location, depth, bottom configuration, distance from 

 shore, and the biological, physical, and chemical condi- 

 tions of the overlying water. Therefore, although a ge- 

 netic classification must take such variables into ac- 

 count, it is desirable to express the effects of these fac- 

 tors in terms of the physical characters and composition 

 of the sediments. A further requisite of the qualities 

 selected is that they should be clear-cut and easily as- 

 certainable in order that they may be readily employed 

 as criteria for distinction between the various types of 

 deposits. 



Physical Characters and Composition 

 of Recent Sediments 



Let us now consider the nature and significance of 

 certain of the physical and chemical characters of re- 

 cent sediments, namely color, texture, chemical compo- 

 sition, and physical composition. 



Color . The colors of most deep-sea deposits vary 

 between reddish -brown to white on the one hand, and 

 grayish-blue, green, or black to white on the other. A 

 red-brown color indicates the presence of ferric hydrox- 

 ide or oxide either as separate particles or as a constit- 

 uent of clay minerals and, therefore, an oxidizing poten- 

 tial as far as ferrous iron is concerned. A grayish-blue 

 or black color usually indicates the presence of hydro- 

 troilite (ferrous sulphide) together with finely divided or- 

 ganic matter, therefore a reducing potential as far as 

 ferric iron is concerned. A greenish color may be owing 

 to the presence of much finely divided organic matter or 



to that of glauconite and related minerals and, therefore, 

 most probably indicates a slightly reducing potential, ac- 

 cording to Hadding (1932). When an oxidizing potential, 

 as shown by a red or brown color, exists below the sur- 

 face of a deposit, it implies that decomposition of the 

 organic matter in the sediments has taken place under 

 aerobic conditions (therefore presumably at or near the 

 surface) either completely to CO2 and water or, as 

 claimed by Waksman (1933), to relatively undecompos- 

 able components, such as lignins. Other things being 

 equal, this must mean either a relatively slow rate of 

 deposition of the organic matter or of the sediment as a 

 whole. On the other hand, a reducing potential, indicated 

 by a grayish-blue, green, or black color, beneath the 

 surface of a sediment means that the decomposition of 

 organic matter is taking place under anaerobic conditions. 

 This usually implies a relatively rapid rate of deposition 

 of both organic and inorganic constituents. 



Somewhat similar ideas as to the significance of 

 color were long ago advanced by Boggild (1906), who 

 says, with reference to certain clays collected by the 

 Fram expedition in the North Polar Sea off the Siberian 

 coast, that the color of the clay is "a tolerably pure 

 gray near the coast, while further out in deep water it 

 acquires an increasingly brown tone and in the deepest 

 places is almost pure brown .... the color of each spe- 

 cies of clay depends as a rule exclusively upon the color 

 of the clayey matter itself and is due to the precipitation 

 of hydrated peroxide of iron on the separate clay parti- 

 cles." Furthermore, "it seems necessary to assume 

 that the transformation of the gray clay to brown can 

 only take place in the very uppermost, extremely thin 

 layer, that is in immediate contact with the sea water, 

 for otherwise all the mud upon the bottom could not but 

 acquire the same brown color .... the only possible 

 explanation appears to be that the gray clay is deposited 

 so much more rapidly than the brown that the uppermost 

 layer has not time to be changed before it is covered 

 with new sediment .... this circumstance is very im- 

 portant in estimating the relative rapidity with which the 

 various sea bottom deposits are formed. Thus, where 

 the conditions in the main are uniform, and where there 

 is no great variation in the composition of the sediments 

 that are carried out into the sea, we may assume that the 

 rapidity with which the deposition takes place is about 

 (inversely) proportional to the amount of brown in the 

 color of the sample. It is not impossible, however, that 

 several different factors, such as temperature, currents, 

 etc., may modify the conditions to some extent. The 

 amount of lime it contains does not seem to influence the 

 color of the clay in any way, except in giving it a lighter 

 shade." 



