Most of the current 50,000-year-long 14C calibration curve is based on decadal resolution, i.e. 10-year averages of tree rings. We are building a high-precision calibration curve for two periods, based on annual or bi-annual samples of Danish oak trees. We cut 200 slices of dendrochronologically dated oak tree rings and extract their cellulose. We radiocarbon date them with extra high precision to form the groundwork of our projects. One period, 800-900 CE, will mainly be applied to radiocarbon dates from Ribe, the oldest town in Scandinavia. The other period, 650-750 CE, will mainly be used for Jerash, a Roman/Islamic city in Jordan. Our new calibration curves will be applied to make age models of the two cities, which incorporate archaeological/historical information. Combining Bayesian modelling, the new calibration curves and several dated events from the locations, the precision on each single dated event will be much higher than previously. In Ribe, we dated samples during the ongoing excavation to inform further sampling. At the Aarhus AMS Centre, we are using a newly developed automated pre-treatment system. It enables us to date larger numbers of samples, primarily charcoal and wood, thus providing better statistics for the age models.
