CALIBRATION OF THE C-14 TIMESCALE OVER THE PAST 30,000 YEARS USING MASS-SPECTROMETRIC U-TH AGES FROM BARBADOS CORALS

Uranium-thorium ages obtained by mass spectrometry from corals raised off the island of Barbados confirm the high precision of this technique over at least the past 30,000 years. Comparison of the U-Th ages with 14C ages obtained on the Holocene samples shows that the U-Th ages are accurate, because they accord with the dendrochronological calibration. Before 9,000 yr BP the 14C ages are systematically younger than the U-Th ages, with a maximum difference of ∼3,500 yr at ∼20,000 yrBP . The U-Th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration. © 1990 Nature Publishing Group.