14C ages of 43 consecutive single-year tree rings between 2710 and 2655 cal BP using accelerator mass spectrometry

We have measured the radiocarbon ages of 43 consecutive single-year tree rings using accelerator mass spectrometry (AMS) with a statistical accuracy of similar to 2.3%o. AMS C-14 ages of the 36 viable samples are between 2708 and 2666 cal BP, a period in which the Delta C-14 of the lntCal04 curve (Reimer et al. 2004) shows an enhancement. The C-14 ages of the samples are scattered with a Gaussian distribution around the interpolated lntCal04 calibration curve. The time profile of the deviations of the 36 C-14 ages from the interpolated IntCal04 calibration curve indicates a linear trend and a characteristic variability rather than a random fluctuation around the curve. The trend indicates a higher gradient than that of the interpolated IntCal04 calibration curve. The profile implies a periodic variation of approximately 11 yr and an amplitude of roughly 18 C-14 yr.