Copenhagen Natural Radiocarbon Measurements III, Corrections to Radiocarbon Dates Made with the Solid Carbon Technique

Abstract

In the Copenhagen I and II date lists radiocarbon dates for samples representing the late-glacial Aller⊘d oscillation and early Neolithic periods in Switzerland and Denmark were given. At the time of publication no account was taken of the dilution of the atmosphere with inactive carbon by the extensive combustion of fossil fuels since the Industrial Revolution (Suess, 1955), and of its influence on the dating results. This effect as measured by Suess amounted to 3.4% depletion in wood samples from the heavily industrialized east coast of the United States. Several later measurements have shown that the magnitude of this reduction in atmospheric C¹⁴concentration varies in different areas. The average universal decrease was calculated by Fergusson (1958) as 2.03 ± .15%. However, the magnitude of reported Suess effects may vary with the chosen reference sample as a result of periodic changes (de Vries effect) in the atmospheric C¹⁴concentration as found by de Vries (1958).