Regional offsets from Northern Hemisphere radiocarbon (14C) calibration curves are widely recognized for monsoon Asia and often hinder accurate 14C dating. In this paper, we explore the possible linkage between summer monsoon intensity and 14C offsets using tree-ring δ18O and 14C data from Thailand. We developed a 297-yr floating tree-ring δ18O chronology comprising seven teak log-coffin samples from the Ban Rai rock shelter site, northwestern Thailand. The outermost ring of our chronology was estimated to date from 358–383 CE, within a 95.4% (2σ) probability range, based on a total of 10 14C measurements that were wiggle-matched against a mixed calibration curve evenly weighted from the IntCal20 and SHCal20 curves. Backward trajectory analysis showed that an intensified (weakened) summer monsoon detected in a modern tree-ring δ18O chronology was most likely to be induced by increased (decreased) air mass transport from the tropical Indian Ocean, which is an area of intense upwelling where the 14C concentration is lower than the atmospheric 14C level. However, partly because of the limited sample size and dating uncertainty, the direct linkage between the tree-ring δ18O series and 14C records obtained from our teak log-coffin samples could not be statistically verified.

Archaeological excavations unearthed three burial mounds between 1983 and 1986 at Fehérvárcsurgó (Hungary). Based on the archaeological determination the site was dated to the Early Iron Age. A complex wooden architecture was observed in the largest tumulus containing inner and outer beam constructions separated by stone blocks. Dendrochronological and radiocarbon (14C) analyses were performed on conserved logs (n=5) to constrain the felling date of the timber, identified as oak, and the construction period of the tumuli. The four longest ringwidth series were synchronized providing a 153-yr-long floating chronology. Five blocks were removed from the cross sections and accelerator mass spectrometry (AMS) 14C analysis was performed on the separated α-cellulose. A wiggle-matching procedure was employed as the 14C ages were in agreement with their relative position in the tree-ring sequence and concurred with the expected archaeological period. The calibrated age range of the last extant ring is 747–707 cal BC (95.4%). The earliest possible felling date of the trees used in the construction was between 735 and 695 BC considering the missing sapwood. This is the first 14C dated tree-ring width chronology from the Early Iron Age in Hungary providing a valuable reference for dendroarchaeological studies along the eastern border of the Hallstatt Culture.

The pattern of climate change in the Southern Hemisphere during the Younger Dryas (YD) chronozone provides essential constraint on mechanisms of abrupt climate change only if accurate, high-precision chronologies are obtained. A climate reversal reported previously at Kaipo bog, New Zealand, had been dated between 13,600 and 12,600 cal yr B.P. and appeared to asynchronously overlap the YD chron, but the chronology, based on conventionally radiocarbon-dated bulk sediment samples, left the precise timing questionable. We report a new high-resolution AMS 14C chronology for the Kaipo record that confirms the original chronology and provides further evidence for a mid-latitude Southern Ocean cooling event dated between 13,800 and 12,400 cal yr B.P. (2σ range), roughly equivalent to the Antarctic Cold Reversal.