GEOLOGICAL RECORD ON THE OCEAN FLOOR 



141 



Fig. 6. Stations where an ash layer was sampled by the piston corer are shown 

 by filled circles. Heavy lines indicate those parts of the track of the Vema along 

 which a subbottom layer was recorded by the echo sounder. Ewing, Heezen, and 

 Ericson have assumed that the subbottom reflection is caused by volcanic ash, and 

 that this forms a continuous layer with a minimum extent over the area shown in 

 the figure (Worzel, 1959). 



mined, namely quartz, has been studied in some detail in the 

 Pacific and shows a distribution of considerable interest. 



Investigations of the size frequencies of the quartz particles in 

 pelagic sediments (Fig. 9) showed a high degree of sorting, a mean 

 diameter in fine silt, and an unusual cutoff of the very small 

 particle sizes indicating an eolian origin of the material in several 

 cases. Subsequent measurements by Goldberg and Rex (1958) 

 support this view in several independent ways, and indicate the 

 existence of two zonal maxima, in each hemisphere around 30° 

 Lat, with a markedly increased content of quartz in the form of 

 fine silt (Fig. 10). Goldberg and Rex have ascribed these maxima 

 to fallout from the jetstreams which with high wind velocities 

 circle the globe in these two latitudinal zones on the border between 

 the stratosphere and the troposphere. The difference in intensity 



