Tree ring dating using oxygen isotopes: a master chronology for central England

Ring-width dendrochronology, based on matching patterns of ring width variability, works best when trees are growing under significant environmental (climatic) stress. In the UK, and elsewhere in the temperate mid-latitudes, trees generally experience low stress, so dating is more difficult and often fails. Oxygen isotopes in tree rings passively record changes in the isotopic ratios of summer precipitation, so they carry a strong common signal, which offers potential for cross-dating. A master chronology covering the period 1200-2000 ce was constructed using the oxygen isotope ratios of the latewood cellulose of oak samples from central England. Two independent chronologies, developed to verify the isotopic signal, were combined (n = 10 trees) and the method was evaluated by dating timbers of known age and historical timbers that could not be dated by ring-width dendrochronology, from both within and beyond the central England region. The agreement between samples and the master chronology is exceptionally strong, allowing the dating of timbers with far fewer rings than is normally the case for ring-width dendrochronology. Tree-ring oxygen isotope values are more suited to correlation analysis than tree-ring widths, so it is possible to provide t-values that conform to Student's t-distribution and can be converted into probabilities of error. A protocol for assigning dates using 'stable-isotope dendrochronology' is proposed, which has the potential to revolutionize the dating of wooden structures and artefacts, allowing the dating of short and invariant ring sequences from young, fast-grown trees. Such samples are commonplace throughout the historical building and archaeological records and were, until now, considered impossible to date.