DEEP-SEA DEPOSITS 79 



natural, therefore, that deep-sea sediments should dis- 

 play differences in composition, not only from one 

 locality to another but also with their depth below the 

 sediment surface. Granting that deposition has pro- 

 ceeded undisturbed through millions of years, one would 

 expect a core of sediment stamped out of the sea bottom 

 to display in its different layers effects of the changes 

 which have taken place during the time required for 

 deposition, in other words to represent an abstract of 

 what one might call "records of the deep," just as geol- 

 ogists working on the continents are wont to regard 

 their profiles of sedimentary material on land as "records 

 of the rocks." 



However, these latter records have in most cases been 

 exposed to attacks from temperature changes, wind, 

 frost, and running water, giving rise to erosion which 

 has sometimes eliminated chapters or even whole 

 volumes of the sequence. The "records of the deep," 

 on the other hand, protected under thousands of feet 

 of sea water, should represent, one would expect, un- 

 broken sequences with no parts missing. 



These expectations have been largely fulfilled by 

 scrutiny of the hundreds of long sediment cores raised 

 by Swedish expeditions, first from the "Skagerak" and 

 later from the "Albatross." In relatively few cases — 

 mostly in cores from great depths, containing red clay — 

 does such a long core present to the eye a homogeneous 

 appearance. Usually the cores display a stratification, 

 with differences in structure and color; and the inter- 



