146 



HISTORY OF THE OCEANS 



Sphsru/es per kg sa/t- and corbonafe-free jet/iment 

 fOOO ^000 JOOO ^000 5000 



100 



200 



300 - 



^00 - 



500 - 



Fig. 11. Concentration of cosmic spherules in a sediment core from the West 

 Pacific. The different curves represent results obtained by slightly different methods 

 of assay (Pettersson and Fredriksson, 1958). 



and the Indian oceans; in addition, several significant minor 

 variations are found in older strata. Radiocarbon data, combined 

 with stratigraphic measurements, appear to confirm that the 

 recent increase in the concentration of cosmic spherules is due to 

 an increase in their rate of accretion on the earth rather than to 

 dilution with a larger amount of other sedimentary components. 

 The original idea by Murray and Renard (1891) that the 

 spherules are solidified droplets of molten iron splashed off from 

 meteorites entering the atmosphere has been further corroborated 

 through elegant microradiographic analyses by Castaing and 



