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.