# Xxxsexey - Is dendrochronology absolute 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.

It is also called “radiocarbon” because it is unstable and radioactive relative to carbon-12 and carbon-13.

Carbon consists of 99% carbon-12, 1% carbon-13, and about one part per million carbon-14.

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.

Nowadays, the internationally agreed upon calendar calibration curves reach as far back as about 48000 BC (Reimer et.

al., INTCAL13 and Marine13 radiocarbon age calibration curves 0 – 50000 yrs cal BP, Radiocarbon 55(4), 2013).They can determine the exact calendar year each tree ring was formed.Dendrochronological findings played an important role in the early days of radiocarbon dating.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.Tree rings provided truly known-age material needed to check the accuracy of the carbon-14 dating method.