‘Wiggle Matching’ Radiocarbon Dates

Abstract

ABSTRACT. This paper covers three different methods of matching radiocarbon dates to the 'wiggles' of the calibration curve in those situations where the age difference between the 14 C dates is known. These methods are most often applied to tree-ring sequences. The simplest approach is to use a classical Chi-squared fit of the 14 C data to the 14 C curve. This gives the calendar date where the data fit best and allows tests of how good the fit is. The only drawback of this method is that it is difficult to ascertain the uncertainty in the date found in this way. An extension of this technique uses a Monte-Carlo simulation to sample possible 14 C concentrations consistent with the measurement made and for each of these possibilities performs a Chi-squared fit. This method yields a distribution of values in the calendrical time-scale, from which the overall dating uncertainty can be derived. A third, rather different approach, based on Bayesian statistics, calculates the relative likelihood of each possible calendar year fit. This can then be used to calculate a range of most likely dates in a similar way to the probability method of 14 C calibration. The theories underlying all three methods are discussed in this paper and a comparison made for the fitting of specific model sequences. All three methods are found to give consistent results and the application of any one of them depends on the nature of the scientific question being addressed.

Tropical cloud forest climate variability and the demise of the Monteverde golden toad

“…The older (1900-1949) portion of the chronology has an estimated maximum age model error of AE2 yr due to slower growth rates and lower radiocarbon precision. The actual calendar dates that could be realistically associated with the radiocarbon assays, particularly on MV15, can be better constrained using Bayesian probability estimates between the radiocarbon calibration curve and the sample measurements (52)(53)(54). The likely dates are restricted foremost by the growth orientation of the tree-that is, samples from near the bark must be more recently formed than those near the center of treeand secondly using the number of annual cycles between each Δ 14 C measurement, in order to determine the most probable interval spanned by the core.…”

Calendar Age of Lisakovsky Timbers Attributed to Andronovo Community of Bronze Age in Eurasia

“…14 C wiggles were matched visually with the 10-yr point spaced calibration curve (CalPal2007_Hulu; see http:// www.calpal.de/calpal/manual) by plotting against each other. Further, a Monte Carlo simulation tested a fit employing the GaussWM program (see Weninger 1997;Bronk Ramsey et al 2001).…”

Calendar Age of the Baigetobe Kurgan from the Iron Age Saka Cemetery in Shilikty Valley, Kazakhstan

“…14 C wiggle-matching (Bronk Ramsey et al 2001) of the four CH3 dates yields high agreement indexes (>89-110%) for most of the dates ( Figure 5). Only one date (3CH3) has poor correspondence with the sequenced group (agreement index 1.2%), but elimination of this one does not change the calibration results much.…”