CLASSIFICATION OF RECENT DEEP-SEA SEDIMENTS 



of the calcium carbonate. Phosphate and manganese 

 nodules are not abundant in Globigerina ooze according 

 to Murray and Renard, but in the southeast Pacific the 

 Globigerina oozes are often very high in manganese. 

 The inorganic residue of pelagic oozes was thought by 

 Murray and Renard to be nothing more than red clay. 

 On the other hand, as will be shown subsequently, there 

 is, in the south Pacific at least, a marked distinction be- 

 tween the noncalcareous parts of certain of the Globig- 

 erina oozes and red clays from the same region, the 

 residue from the Globigerina oozes having a much lower 

 silica sesquioxide ratio than any red clays which have 

 been collected hitherto. 



5. Green mud and sand (French, Boue et sable vert; 

 German, Grun-Sande-und Schlicke). Recent green sands 

 were described first by Bailey (1851) and Pourtales 

 (1853) from off the Atlantic coast of the United States. 

 The term "green mud" was used by the Challenger 

 workers for the finer-grained equivalent of green sand. 

 These deposits are said to be found most characteristi- 

 cally on continental slopes off high and bold coasts, 

 where the rate of deposition is slow. The seventeen At- 

 lantic samples described by Murray and Chumley are 

 said usually to be gray rather than green when dry, al- 

 though often with a green tinge. They have sometimes a 

 brown tinge and are rarely bluish. The structure is 

 only slightly coherent and is granular, owing to the pres- 

 ence of glauconite grains. Glauconite is, by definition, 

 present in all samples. There are many green-colored 

 sediments, however, in which the presence of glauconite 

 is doubtful. These were called blue muds by Murray 

 and Renard, although a more logical system of designa- 

 tion would be the naming of all fine-grained green- 

 colored sediments as green muds, separating those 

 containing glauconite as glauconitic muds.l 



6. Pteropod ooze (French, Vase a pteropodes; Ger- 

 man, Pteropodenschlamm). This name was employed by 

 Murray in 1876 to distinguish those deposits formed in 

 warm waters of moderate depth, on oceanic ridges and 

 cones usually far from continental land, which are char- 

 acterized by the presence of a great number and variety 

 of pelagic organisms, notably pteropod and heteropod 

 shells. The Atlantic pteropod oozes are usually light 

 •brown or almost white in color when dry, often with a 

 gray, reddish, pink, or yellow tinge. They are only 

 slightly coherent and usually are coarsely granular, 

 many of the pteropod shells being macroscopic in size. 

 This deposit is perhaps best regarded as a variety of 

 Globigerina ooze. 



7. Radiolarian ooze (French, Vase a radiolaires; 

 German, Radiolarienschlamm). This name was used by 

 Murray in 1876 to designate those deposits found in the 

 central Pacific and later in the Indian Ocean which, 

 "while resembling red clays in most respects, differ 

 from them in containing a much larger number of radio- 

 larian shells, skeletons, and spicules, together with 

 sponge spicules and the frustules of diatoms." These 

 sediments are red, chocolate, or occasionally straw col- 

 ored, and less plastic than the red clay. Argillaceous 

 matter is always present, and is often formed into irreg- 

 ular agglomerations which do not break up under the 

 action of acid, and may be cemented by colloidal silica. 



'^Neaverson (1934) has suggested the use of the term 

 glauconitic muds for green muds which contain glauco- 

 nite; and has introduced the term diatomaceous mud for 

 most nonglauconitic green muds. 



"Peculiar white-colored aggregations composed of mi- 

 nute rhombohedral crystals," believed to be calcite or 

 dolomite, are usually present. 



8. Red clay (French, Argile rouge; German, Roter 

 Tief-See Ton). This deposit was first discovered by the 

 Challenger between Teneriffe and the West Indies, and 

 was described in 1874 by Wyville Thomson, who be- 

 lieved that it was primarily of organic origin, being 

 "essentially the insoluble residue, the ash, as it were, 

 of calcareous organisms." Murray, in 1877, claimed 

 that the clay was derived from the decomposition of vol- 

 canic ejecta, but he admitted that "colloid clayey 

 matter coming in suspension from the land may play 

 some part in the formation of this deposit." The red 

 clay is spread over the greater depths of the ocean far 

 from land and is the most widely distributed of all deep- 

 sea deposits. In the north Atlantic and some other re- 

 gions the color is brick red from the presence of ferric 

 hydroxide, intimately mixed with the clay. In the south 

 Pacific and the Indian oceans the color is often chocolate 

 brown from the presence of minute grains of manganese 

 dioxide. Some of the samples collected relatively near 

 shore and described as red clays had a bluish rather 

 than red tinge owing to the presence of ferrous sulphide 

 and organic matter. Similarly, certain gray Albatross 

 samples collected near the South American coast were 

 called red clays by Murray and Lee (1909). The red 

 clay is plastic and greasy to the touch when wet. When 

 dry it is very coherent. 



9. Red mud (French, Boue rouge; German, Roter 

 Schlick). Red mud was described first in 1876 by Mur- 

 ray, who regarded it as a local variety of blue mud found 

 in certain regions, such as the Yellow Sea and off the 

 coast of Brazil, where great rivers bring down "large 

 quantities of ochreous matter" and in which the rate of 

 accumulation of organic matter is not sufficient to re- 

 duce the large amounts of ferric oxide. Ten samples 

 described by the Challenger from the Brazilian coast 

 were all red brown in color. The mineral assemblage is 

 said by Murray and Renard to be similar to that of other 

 terrigenous deposits along the continental shores, ex- 

 cept that glauconite is never present. 



10. Volcanic mud and sand (French: Boue et sable 

 volcanique; German, Vulkanische Schlicke und Sande). 

 This name was given by Murray in 1876 to the muds and 

 sands found around volcanic islands which contain large 

 amounts of volcanic material. The color is usually 

 brownish gray or grayish brown, occasionally with a 

 green or blue tinge. The structure is ordinarily only 

 slightly coherent. Glauconite is usually absent. 



From a study of the above descriptions and of the 

 values given in the tabular summary for the character- 

 istics and composition of the various deposit types, it 

 will be seen that it is usually possible to express the 

 Murray classification of recent deep-sea sediments 

 (which is based on assumed origin of the sediments and 

 geographical location) in terms of the physical and 

 chemical composition and characters of these sediments 

 themselves, even though the maximum and minimum 

 values given for several of the deposit types overlap. 



The criteria for the recognition of pelagic deposits, 

 as identified by Murray and his co-workers, may be 

 stated as either (1) the presence of more than 30 to 40 

 per cent of predominantly pelagic organic remains, or 

 (2) the absence of notable amounts of detrital or volcan- 

 ic minerals (except in deposits far from land), usually 

 together with a reddish or brownish color. Thus a red 



