The terrigenous deposits consist of blue muds, red muds (abundant along the coast of Brazil, where the amount of organic matter present is insufficient to reduce the iron in the matter brought down by the great rivers to produce blue muds), green muds and sands, and volcanic and coral detritus.
Hemipelagic deposits are a mixture of deposits of terrigenous and pelagic origin.
The most abundant of the terrigenous materials are the finest particles of clay and calcium carbonate as well as fragments derived from land vegetation, of which twigs, leaves, &c., may form a perceptible proportion as far as 200 m.
Terrigenous Deposits (formed in deep or shallow water close to land) by a calcareous cement.
The terrigenous ingredients in the deposits become less and less abundant as one goes farther into the deep ocean and away from the continental margins.
As well as the finest of terrigenous clay there is present in sea-water far from land a different clay derived from the decomposition of volcanic material.
Hence the proportion of purely oceanic area to the total area is greater in the Pacific than in the Atlantic, the supply of detritus being smaller, and terrigenous deposits are not borne so far from land.
All the enclosed seas are occupied by characteristic terrigenous deposits.