144 



HISTORY OF THE OCEAN'S 



Quartz 



Sum of other 



minero 



components 



100 >i 



Fig. 9. Size frequency distribution of quartz and of the sum of other mineral 

 components in a clay sediment from the north equatorial Pacific (Arrhenius, 1954, 

 unpublished). 



maximum suggest a total contribution of windborne minerals to 

 the pelagic sediments in this zone of perhaps twice this value, and 

 emphasize the quantitative importance of eolian components in 

 some pelagic sediments. Strangely enough, no significant variations 

 in this contribution have been found between the glacial and 

 interglacial stages. The Tertiary sediments in the north equatorial 

 Pacific, however, are low in quartz, indicating smaller arid source 

 areas, or less efficient transport, and in the upper Pliocene a 

 gradual transition is found from this situation to present-day 

 conditions. 



The importance of accretion of cosmic dust and micrometeorites 

 was realized during the first extensive investigations of deep sea 

 sediments by Murray and Renard (1891) after the Challenger 

 expedition during the last century; however, it was left to the 



