Archive image from page 200 of The depths of the ocean;. The depths of the ocean; a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic depthsofoceange00murr Year: 1912 iv DEPTHS AND DEPOSITS OF THE OCEAN 163 in the surface waters, and where there is abundant secretion of silica by the plankton organisms. Over wide areas in very deep water, however, neither cal- careous nor siliceous remains predominate ; the basis of the deposit then becomes Red clay, consisting of clayey matter derived f
Archive image from page 200 of The depths of the ocean;. The depths of the ocean; a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic depthsofoceange00murr Year: 1912 iv DEPTHS AND DEPOSITS OF THE OCEAN 163 in the surface waters, and where there is abundant secretion of silica by the plankton organisms. Over wide areas in very deep water, however, neither cal- careous nor siliceous remains predominate ; the basis of the deposit then becomes Red clay, consisting of clayey matter derived from the decomposition of vol- canic materials ; quartz particles, so abundant in terrigenous deposits, are rare or absent. The pelagic deposits are subdivided into the following types, viz. :— Pteropod Ooze.— In Pteropodooze, the shallower waters, usually far from continental land, on oceanic ridges and cones, especially within coral reef regions where warm water with small annual range occupies the surface, almost every surface organism which secretes a hard shell or skeleton is represented in the de- posit, the dead shells of pteropods and hetero- pods being character- istic, and the deposit is hence called Pteropod ooze (see Fig. 136). About 35 species of pteropods and 32 species of heteropods, as well as pelagic gas- teropods (see pp. 172- 173), are known to live in the surface waters of the tropics, and Fig. 136.—Pteropod Ooze. Valdivia' Station 208, Indian Ocean, lat. 6° 54' N., long. 930 28'.8 E.( 162 fathoms (magnified).
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