Validation of the supra-long pine tree-ring chronologies from northern Scandinavia

We empirically demonstrate that acceptance thresholds for a dendrochronological cross-match of at least t=6 for oak and at least t=7 for pine are required when constructing independent tree-ring master chronologies. These thresholds are far above the "thresholds for significant matches" of t=3.5 or t=4 adopted forty years ago, which are still regarded appropriate for the dating of archaeological samples. We also validate the supra-long Scots pine chronologies from northern Scandinavia using these tightened criteria and our crossdating software CDendro.

The Finnish and Swedish pine chronologies were built by two concurrent teams of scientists working with wood from different places and with different methods. Both teams arrived at the same conclusion regarding the overall dendro signal for the past 7500 years. Our reassessment confirms this conclusion, and demonstrates that both teams worked on a firm level of confidence when accepting dendrochronological matches. This validation is vital for the credibility of our hypothesis about general errors in the European oak masters, errors which were probably caused by using pre-dating with other methods in cases when sufficient dendrochronological confidence levels could not be reached.

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