342 Hans Pettersson 



The first attempt to utilize the ionium-precipitation hypothesis for a submarine 

 geochronology, based on radium measurements, was made in the early 70's by 

 C. S. PiGGOT and W. D. Urry (1941) and by Urry (1949). Their first results, obtained 

 from fairly long sediment cores from the Caribbean and the N, Atlantic Ocean 

 (published as curves only), gave hopes of realizing a dependable method of dating 

 different layers of a sediment core and of obtaining values for the rate of sedimentation 

 from radium measurements. More extensive measurements on cores from the 

 Swedish Deep-Sea Expedition, started after the return of the Expedition, are now 

 being published by V. Kroll, who has for some years been working in Goteborg 

 (1955). The results prove that the vertical distribution of radium in the cores is much 

 more complicated than the ionium-precipitation hypothesis alone would imply. 

 Often two, three, or even more maxima, beside that to be expected from radioactive 

 equilibrium, Ra/Io, are actually found. 



The opportunities offered by the Swedish Deep-Sea Expedition for studying the 

 radioactivity of the ocean were used for an extensive sampling for radium analyses 

 of large-volume water samples. After the return of the Expedition, the barium- 

 sulphate precipitates were analyzed for radium, partly by the present author in Gote- 

 borg and partly in Vienna by Dr. Traude Bernert. The results, which have not been 

 published before, are here set out in Table IV. They are seen to confirm our earlier 

 results, viz. that the radium present in the ocean waters is only a small fraction of the 

 quantity in equilibrium with dissolved uranium. In addition, uranium measurements 

 on most of the water samples were carried out in Vienna by G. Koczy (1950), with 

 results agreeing with those found earlier by Hernegger and Karlik. There cannot 

 then be any doubt about the partial disappearance from the ocean waters of the radium 

 produced from dissolved uranium. 



However, a missing link in the chain of evidence concerns the presence of ionium. 

 in the deposits and in the water. Thanks to an ingenious method for photographic 

 (nuclear-plate) determinations of ionium. Dr. E. Picciotto and his co-workers in the 

 Institut des Recherches Nucleaires of the Universite Libre in Brussels, have been able 

 to measure the ionium contained in sediments from the Swedish Deep-Sea Expedition 

 (1954). It was found that, within the limits of experimental accuracy, the ionium 

 present is in radioactive equilibrium with the radium in the same sample, except in 

 the very uppermost surface layer, where there is an excess of ionium. On the other 

 hand, more recent measurements of the ionium present in sea water, carried out by 

 Picciotto and F. Koczy, have proved the ionium content to be extremely low, lower 

 even than what could correspond to the radium content, which in itself, as we have seen, 

 is only a fraction of the equilibrium value with dissolved uranium. 



This result raises a problem of considerable interest. Since the scarcity of ionium 

 in ocean water negatives the assumption that the radium in the water is produced 

 in situ from its parent element ionium, the question arises, from what source is the 

 radium contained in the ocean water derived ? 



Dr. F. Koczy has proposed an explanation, put forward in a paper read before 

 the meeting of the I.U.G.G. in Rome in Sept. 1954, that oceanic radium is dissolved 

 through a chemical interaction between the bottom water and the uppermost 3-5 cm 

 sediment layer. From the bottom water the radium is spread upwards through the 

 water masses by diff'usion, aided by turbulence. This view Koczy finds supported 

 by the curves in Fig. 3, giving the vertical distribution of the radium in the water 



