Discussion: Reporting and calibration of post-bomb ¹⁴C data

The definitive paper by Stuiver and Polach (1977) established the conventions for reporting of radiocarbon data for chronological and geophysical studies based on the radioactive decay of ¹⁴C in the sample since the year of sample death or formation. Several ways of reporting ¹⁴C activity levels relative to a standard were also established, but no specific instructions were given for reporting nuclear weapons-testing (post-bomb) ¹⁴C levels in samples. Because the use of postbomb ¹⁴C is becoming more prevalent in forensics, biology, and geosciences, a convention needs to be adopted. We advocate the use of fraction modern with a new symbol F¹⁴C to prevent confusion with the previously used Fm, which may or may not have been fractionation-corrected. We also discuss the calibration of post-bomb ¹⁴C samples and the available data sets and compilations, but do not give a recommendation for a particular data set.