RADIOACTIVE ELEMENTS AND DEEP-SEA SEDIMENTS 373 



Table I. Natural Radioactive Nuclides Present in the Ocean" 



Half life, Concentration, Isotopic Disintegrations, 



Nuclide years g/ml abundance, % per sec and per ml 



" Concentrations in surface waters in 1953, prior to thermonuclear tests. 

 b For references to literature see text. 



discussed in greater detail in articles by Holland and Kulp (1954), 

 Koczy et al. (1957), and Suess (1958). 



Let us now consider the nuclides of the three radioactive 

 families, and their radioactive equilibrium states, these equi- 

 librium states being the basis for the methods of chronology of 

 the sediments. We must remember that any two nuclides belonging 

 to the same family undergo the same number of disintegrations 

 per second when the family is in radioactive equilibrium. Column 4 

 of Table I permits a rapid check of the equilibrium state. 



The earliest measurements of uranium in the ocean were carried 

 out by Hernegger (1933) and later by Hernegger and Karlik (1935). 

 Their results subsequently were confirmed by a number of other 

 authors. The majority of reported results indicate concentrations 

 of between 1 X 10-^ and 3 X 10-^ g/ml; the accepted average 

 value is 2 X 10"^ g/ml. 



Measurements on radium were carried out by two independent 

 groups, that of Evans (Evans et al., 1938) and that of Pettersson 

 (F0yn et al., 1939). A large number of determinations was carried 



