Modeling Atmospheric ¹⁴C Influences and ¹⁴C Ages of Marine Samples to 10,000 BC

TLDR

Radiocarbon calibration using tree‑ring data provides precise age standards, but organisms from non‑atmospheric reservoirs have initial ¹⁴C activities that differ from the contemporaneous atmosphere, so their measured ¹⁴C reflects both decay and reservoir effects. Because conventional ¹⁴C age calculations incorporate measured sample activity, differences in reservoir ¹⁴C lead to apparent age offsets between contemporaneous samples from different reservoirs.

Abstract

The detailed radiocarbon age vs. calibrated (cal) age studies of tree rings reported in this Calibration Issue provide a unique data set for precise 14 C age calibration of materials formed in isotopic equilibrium with atmospheric CO 2 . The situation is more complex for organisms formed in other reservoirs, such as lakes and oceans. Here the initial specific 14 C activity may differ from that of the contemporaneous atmosphere. The measured remaining 14 C activity of samples formed in such reservoirs not only reflects 14 C decay (related to sample age) but also the reservoir 14 C activity. As the measured sample 14 C activity figures into the calculation of a conventional 14 C age (Stuiver & Polach 1977), apparent 14 C age differences occur when contemporaneously grown samples of different reservoirs are dated.