Possible subsurface production of carbon-14 in ground water

Abstract

Theoretical mechanisms for the production o1f4 C .in ground water by activation of 14N, 170, and 13C by emissions from uranium and thorium nuclei have been proposed. These mechanisms were investigated in laboratory and field settings to determine applicability in the natural environment and the extent to which error may be introduced in a ¹⁴C date due to in situ ¹⁴C production. Laboratory experiments demonstrated that calculated and measured ¹⁴C production in irradiated samples of ammonium nitrate solution and distilled water agreed within an order of magnitude. The methane and carbon dioxide fractions of a natural gas with a high nitrogen content were ¹⁴C dated. The methane contained no ¹⁴C, but due to analytical difficulties, the ¹⁴C activity of the carbon dioxide could not be accurately ascertained. These investigations indicate that in situ ¹⁴C production will not influence ¹⁴C dating of ground water except under unique circumstances. Only if the source rock is highly enriched in uranium and the sample of water or gas from the source rock has a high concentration of nitrogen may in situ production of ¹⁴C produce an error in a ¹⁴C date if the ¹⁴C dating range is not extended beyond 50,000 BP.