Thermoluminescence dating versus radiocarbon dating
The first calibration curve for radiocarbon dating was based on a continuous tree-ring sequence stretching back to 8,000 years.This tree-ring sequence, established by Wesley Ferguson in the 1960s, aided Hans Suess to publish the first useful calibration curve.If a sample has the same proportion of radiocarbon as that of the tree ring, it is safe to conclude that they are of the same age.In practice, tree-ring calibration is not as straightforward due to many factors, the most significant of which is that individual measurements made on the tree rings and the sample have limited precision so a range of possible calendar years is obtained.Radiocarbon dating laboratories have been known to use data from other species of trees.
Calibration of radiocarbon results is needed to account for changes in the atmospheric concentration of carbon-14 over time.
Suess’s curve, based on the bristlecone pine, used tree rings for its calendar axis.
There have been many calibration curves published since Suess’s curve, but their proliferation brought more problems than solutions.
And indeed, results of calibration are often given as an age range rather than an absolute value.
Age ranges are calculated either by the intercept method or the probability method, both of which need a calibration curve.