Discussion: Reporting and Calibration of Post-Bomb ¹⁴C Data

TLDR

The Stuiver and Polach (1977) conventions for reporting radiocarbon data lack guidance for post‑bomb 14C, prompting the need for a new standard as post‑bomb 14C use expands in forensics, biology, and geosciences. The authors propose adopting fraction modern with a new symbol F14C to avoid confusion with the earlier Fm notation. They describe using F14C and outline calibration procedures for post‑bomb 14C samples, reviewing available data sets and compilations. The study presents these calibration options but does not endorse any particular data set.

Abstract

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.