Calibration of¹⁴C Histograms: A Comparison of Methods

Abstract

The interpretation of 14 C histograms is complicated by the non-linearity of the 14 C time scale in terms of calendar years, which may result in clustering of 14 C ages in certain time intervals unrelated to the (geologic or archaeologic) phenomenon of interest. One can calibrate 14 C histograms for such distortions using two basic approaches. The KORHIS method constructs a 14 C histogram before calibration is performed by means of a correction factor. We present the CALHIS method based on the Groningen calibration program for individual 14 C ages. CALHIS first calibrates single 14 C ages and then sums the resulting calibration distributions, thus yielding a calibrated 14 C histogram. The individual calibration distributions are normalized to a standard Gaussian distribution before superposition, thus allowing direct comparison among various 14 C histograms. Several experiments with test data sets demonstrate that CALHIS produces significantly better results than KORHIS. Although some problems remain (part of the distortions due to 14 C variations cannot be eliminated), we show that CALHIS offers good prospects for using 14 C histograms, particularly with highly precise and accurate 14 C ages.