High-Precision ¹⁴C Measurement of Irish Oaks to Show the Natural ¹⁴C Variations from 200 BC to 4000 BC

Bi-decade samples of dendrochronologically matched Irish Oak, measured with a precision of ca ± 20 years, covering the period 200 to 4000 BC are presented. The data are compared with the published data of Suess, de Jong, and Mook to provide a general calibration of the 14 C time scale for this period. Although the dendrochronologic sequences presented are not absolutely tied to present, the best fit (based on 14 C evidence) of the Belfast data to absolute chronologies, the error and evidence associated with such positioning is given. The intervals chosen for analysis were 20 years, reducing slightly the resolution of short-term variations when compared to 10-year intervals, which are sometimes measured. However, this calibration would suffice for most scientific purposes and certainly for the calendrical conversion of 14 C dates derived from archaeologic samples.