The IntCal20 approach to radiocarbon calibration curve construction: A new methodology using Bayesian splines and errors-in-variables

Timothy J. Heaton*, Maarten Blaauw, Paul G. Blackwell, Christopher Bronk Ramsey, Paula Reimer, E. M. Scott

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

To create a reliable radiocarbon calibration curve, one needs not only high-quality data
but also a robust statistical methodology. The unique aspects of much of the calibration
data provide considerable modelling challenges and require a made-to-measure approach to curve construction that accurately represents and adapts to these individualities, bringing the data together into a single curve. For IntCal20, the statistical methodology has undergone a complete redesign, from the random walk used in IntCal04, IntCal09 and IntCal13, to an approach based upon Bayesian splines with errors-in-variables. The new spline approach is still fitted using Markov Chain Monte Carlo (MCMC) but offers considerable advantages over the previous random walk, including faster and more reliable curve construction together with greatly increased flexibility and detail in modelling choices. This paper describes the
new methodology together with the tailored modifications required to integrate the various datasets. For an end-user, the key changes include the recognition and estimation of potential over-dispersion in 14 C determinations, and its consequences on calibration which we address through the provision of predictive intervals on the curve; improvements to the modelling of rapid 14C excursions and reservoir ages/dead carbon fractions; and modifications made to, hopefully, ensure better mixing of the MCMC which consequently increase confidence in the estimated curve.
Original languageEnglish
JournalRadiocarbon
DOIs
Publication statusAccepted - 01 Jun 2020

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