Comment on “Radiocarbon calibration curve spanning 0 to 50,000 years BP based on paired 230Th/234U/238U and 14C dates on pristine corals” by R.G. Fairbanks et al. (Quaternary Science Reviews 24 (2005) 1781–1796)??doi of original article: 10.1016/j.quascirev.2005.04.007 and “Extending the radiocarbon calibration beyond 26,000 years before present using fossil corals” by T.-C. Chiu et al. (Quaternary Science Reviews 24 (2005) 1797–1808)????doi of original article: 10.1016/j.quascirev.2005.04.002
A recently published radiocarbon calibration curve extending to 50,000 cal BP
(Fairbanks et al. 2005) is purportedly superior to that generated by the IntCal working
group beyond the end of the tree-ring data at 12,400 cal BP (Reimer et al. 2004). This
claim is based, in part, on different diagenetic screening criteria and pretreatment for
coral samples (Fairbanks et al. 2005; Chiu et al. 2005) which do not stand up under
careful scrutiny. Also at issue is the conversion of the coral-based calibration curve to an atmospheric curve where large inter-annual variability in the sea-surface age reservoir age has been observed in the southwest Pacific where one of two sets of corals used were sampled. In addition we comment on the seemingly ad hoc statistical methods utilized by Fairbanks et al. (2005) to construct their curve. We recognize the value of the Fairbanks et al. (2005) coral radiocarbon data set, but reassert the need for multiple, independently derived data to provide confirmation and validation to all radiocarbon calibration data. This is especially important before 26,000 cal BP when lower sea-levels of the last glacial maximum exposed most coral samples to alteration by fresh water.