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 14 C in the sample since the year of sample death or formation. Several ways of reporting 14 C activity levels relative to a standard were also established, but no specific instructions were given for reporting nuclear weapons-testing (post-bomb) 14 C levels in samples. Because the use of post-bomb 14 C 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 F 14 C 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 14 C samples and the available data sets and compilations, but do not give a recommendation for a particular data set.