Dendrochronology absolute dating method
Libraries of tree rings of different calendar ages are now available to provide records extending back over the last 11,000 years.The trees often used as references are the bristlecone pine (Pinus aristata) found in the USA and waterlogged Oak (Quercus sp.) in Ireland and Germany.Results of carbon-14 dating are reported in radiocarbon years, and calibration is needed to convert radiocarbon years into calendar years.
Carbon consists of 99% carbon-12, 1% carbon-13, and about one part per million carbon-14.These changes were brought about by several factors including, but not limited to, fluctuations in the earth’s geomagnetic moment, fossil fuel burning, and nuclear testing.The most popular and often used method for calibration is by dendrochronology.Tree rings provided truly known-age material needed to check the accuracy of the carbon-14 dating method.
During the late 1950s, several scientists (notably the Dutchman Hessel de Vries) were able to confirm the discrepancy between radiocarbon ages and calendar ages through results gathered from carbon dating rings of trees.
Suess’s curve, based on the bristlecone pine, used tree rings for its calendar axis.