6. The Deep-Sea Deposits 

 and Their Stratigraphy 



1 n Chapter 4 a survey was given of the different sources 

 of the sediment carpet covering the basement of our 

 planet, the deep ocean floor. Of the two main sources 

 the continents provide the warp, of inorganic origin: 

 airborne or waterborne particles, microscopic or even 

 submicroscopic in size, which form the deep-sea clay. 

 The ocean itself contributes a woof of biogenetic origin: 

 particles extracted from the sea by a multitude of living 

 organisms, mostly plankton, drifting in the upper layers 

 of water, from which they accumulate either silica or 

 carbonate of lime in the shape of tests or skeletons, 

 which are ultimately deposited on the bottom. A much 

 smaller contribution comes from the bottom-living 

 organisms, the benthos, which are always animals, since 

 daylight, the sine qua non of plant life, is absent in 

 depths exceeding a few hundred feet. 



A third major contributor to the deposits is volcan- 

 ism. After great explosive outbreaks of volcanoes on the 

 continents or on volcanic islands, ash particles, thrown 

 hish into the air, settle down to the sea surface over 



