Tree-ring oxygen isotope cross-dating between southeastern China and central Japan

Long tree-ring chronologies applicable for archaeological dating are extremely rare in southeastern China, limiting dendroarchaeological research in this monsoon region. A large number of archaeological woods have been unearthed in this region, and the application of tree-ring oxygen isotope (δ¹⁸O) allows cross-dating of less climatically stressed trees of different species from distant sites, offering a potential to change the standstill. In this study, we tested tree-ring δ¹⁸O cross-dating of modern and archaeological samples from southeastern China against the central Japan master tree-ring chronology spanning the past 2872 years. Dating experiments on living-tree chronologies of known ages indicate that it is feasible to pinpoint their correct calendar dates using the central Japan master chronology. Cross-dating based on tree-ring width was successfully conducted on 46 Cunninghamia lanceolata samples excavated from Han Dynasty tombs in the Yangzhou area, southeastern China, and the sample with the most recent ring was selected to build a floating tree-ring δ¹⁸O series. The floating series was cross-dated with the central Japan master chronology to produce an unambiguous end date of 2 BCE, which is supported by climate records in historical literature. The success of δ¹⁸O dating is dependent on common signals at both high and low frequencies originating from multi-scale climate coherence between the two regions, and thus long sample series containing decadal to multidecadal variations are necessary. Our study shows a feasibility of δ¹⁸O-based dendroarchaeology in southeastern China.