Radium and Deep-Sea Chronology

Abstract

COLLABORATION between Austrian, Norwegian and Swedish specialists gave the first accurate measurements of the content of uranium and radium in sea water¹. These results have recently been confirmed by measurements on much more extensive material collected during the Swedish Deep-Sea Expedition². Whereas uranium remains fairly constant (average content 1.3 × 10⁻⁶ gm. per litre), the radium content is more variable, averaging about 0.07 × 10⁻¹² gm. per litre or 15 per cent of the theoretical value in equilibrium with the dissolved uranium. I have suggested that this lack of radium in ocean waters is due to precipitation of its parent element ionium together with ferric hydroxide³. This would also explain the surprisingly high radium content found in the surface layer of red clay and radiolarian ooze as ionium-supported radium, decreasing downwards with the half-period of ionium, 83,000 years. Such a falling-off in radium content was first demonstrated in long cores by Piggot and Urry⁴, and has been used in their attempts to estimate the rate of sedimentation.