INVESTIGATIONS OF STRATIGRAPHY 109 



has undergone solution and a subsequent vertical 

 migration in the sediment. The manganese in the shaDe 

 of its peroxide, braunstein, is known to absorb radium, 

 a subject which will be more fully treated in Chapter 8. 

 Also, the iron precipitc^ted from the ocean water is 

 assumed to play a part with regard to the co-precipita- 

 tion of the mother element of radium, namely ionium. 

 Again, part of the abyssal iron may be assumed to have 

 a magmatic origin and to have become extruded on the 

 deep ocean floor at great submarine eruptions. The 

 nickel content of certain deep-sea sediments, especially 

 those characterized by an excessively slow rate of ac- 

 cumulation, may in part be of cosmic origin, derived 

 from meteors or micrometeors entering the earth's at- 

 mosphere from without. The curve reproduced here in 

 Figure 37 shows the distribution of manganese along 

 a core from the Romanche Deep, taken from a forth- 

 coming paper by Berrit. The isolated high peaks in 

 the manganese curve are to be interpreted, I believe, 

 as products of great submarine eruptions, since they 

 occur also in other cores from the equatorial Atlantic. 

 The importance of titanium for submarine geochron- 

 ology emphasized by Arrhenius has already been re- 

 ferred to earher in this chapter. 



To study this problem of the geochronology of the 

 deep ocean sediments has been one of the main ob- 

 jectives of our work. Of the methods so far applied to 

 solve this very fundamental problem three appear 

 promising: (1) analysis of the composition of the 



