41Ca Concentrations in Modern Bone and Their Implications for Dating

Abstract

We have made the first measurements without pre-enrichment of 41Ca in terrestrial rock and bone samples using accelerator mass spectrometry. Although the results in tufa deposits from Egypt are in good agreement with the saturation value of 8 x 10^-15 predicted by Raisbeck and Yiou (1979), the average 41Ca:40Ca ratio of 2x10^-15 (range: 0.6 to 4.2x10^-15) that we measure in modern bone is an order of magnitude lower than that obtained previously by Henning, et al (1987) on a cow bone that was measured using AMS following isotope enrichment. The low value and the variability (more than a factor of seven) of the 4 Ca:40Ca ratio in modern bone make the possibility of dating bones using 41Ca unlikely.