Reconstructing Late Pleistocene Atmospheric Radiocarbon using Subfossil New Zealand Kauri (Agathis australis)
Annually resolved subfossil kauri (Agathis australis) trees, recovered from bogs in northern New Zealand, provide unique insights into past climate events over multi-millennial timescales. Their tree-rings faithfully capture annually resolved information about climate and carbon dynamics occurring during their lifespan. Preserved material has contributed tree-ring chronologies spanning much of the Holocene and extending into the late Pleistocene (i.e. the last 50,000 years). A recently discovered site (called Waipu) has yielded over 40 kauri logs that have resulted in four floating tree-ring chronologies which span a combined total of more than 6,000 years during the time interval of 32,000 - 22,000 years before present (BP). This time period is of great scientific interest as it includes the transition towards the Last Glacial Maximum (LGM) as well as abrupt warming events (Dansgaard-Oeschger events) and an extreme cold event (i.e. Heinrich 3). The preliminary results of the visually cross-matched samples were tested using the recently developed ‘RingdateR’ software as it was specifically designed to deal with unknown-age material. The positive results have meant the approach will be used to help with streamline processing logs from other sites. More logs are currently being measured from the Waipu site, and the final chronologies will be sampled to produce bi-decadal radiocarbon measurements that will help refine the radiocarbon calibration curve. The subsequent dataset of atmospheric radiocarbon content will help provide information to precisely align and date terrestrial, marine and ice core records of climate and environmental events. Offering a potential world-class palaeo-archive for radiocarbon calibration.