The world's longest tree-ring chronology comprises thousands of oak and pine series from Germany and continuously covers the Holocene back to 12,325 cal BP. A lack of relict wood from the Younger Dryas cold reversal ca. 12,900–11,700 cal BP, however, challenges the extension of this absolutely dated ring width record further back in time. Here, we combine 646 high-resolution stable oxygen isotope and 795 radiocarbon measurements from subfossil pines that grew during the Younger Dryas at three different sites near Zurich, Switzerland, to extend the record. Coherency of the oxygen isotope variations secures internal crossdating, and radiocarbon wiggle-matching places the final 425-year-long ring-width chronology between 12,716 and 12,292 cal BP with an uncertainty of ±8 years. Our study describes an important step towards annual dating precision further into the Late Glacial period.

Large tropical tree samples are driving new research in dendrochronology. The development of imaging tools for these substantial samples represents a significant challenge. Specifically, tree-ring measurements are strongly associated with images acquired through scanning, with an A3 large-format scanner being the preferred choice for these sizable samples. However, the literature lacks information about image distortions resulting from this approach. To address this gap, we developed a system comprising a table, a mobile scanner lift, and a fixed sample-support unit. This system ensures the production of aligned composite images of wooden disc samples and safeguards the scanning equipment from damage. To test its efficiency, we evaluated distortions in the measurements of treering widths across various digitized images at nine different heights, ranging from 2 to 10 mm. Remarkably, we observed no distortions in the growth ring measurements at any assessed height. Furthermore, the images of samples positioned 2 mm and 3 mm away from the scanner glass were clear, allowing precise measurements of small growth rings between 0.1 and 0.5 mm in size. Our equipment offers flexibility of use with other models and sizes, including A4 scanners. It can digitize wooden discs with diameters ranging from 60 to 200 cm.