T01_P06

Absolute dating with ¹⁴C and ⁴¹Ca - is it feasible?

Kutschera W¹,   Paul M²

¹University of Vienna, Vienna, Austria, ²The Hebrew University of Jerusalem, Jerusalem, Israel

It is well-known that ‘wiggles‘ and ‘plateaus‘ of the ¹⁴C calibration curve often limit the precision of age determinations. In principle this problem could be avoided by absolute dating [1]. This requires to measure the ‘mother/daughter‘ abundance ratio ¹⁴C/¹⁴N* which is independent of the initial ¹⁴C abundance and only depends on the half-life and the age. Whereas ¹⁴C dating in the ‘classical‘ way is well established – although with the limitations mentioned above – dating with ⁴¹Ca (half-life = 100,000 years) would require absolute dating because a global calibration curve for ⁴¹Ca does not exist. In this case, the abundance ratio of ⁴¹Ca/⁴¹K* has to be measured. In both cases the ubiquitous existence of stable nitrogen or potassium on Earth makes the detection of the feeble radiogenic signals of ¹⁴N* and ⁴¹K* extremely challenging.

It was noted by Szabo et al. [1] that the kinematics of the ¹⁴C beta decay leads to ¹⁴N* recoil energies < 6.9 eV comparable to binding energies of atoms in molecules. Due to the pure electron-capture decay of ⁴¹Ca, the recoil energy of ⁴¹K* is even lower: <2.2 eV: Thus, there exist a certain retention probability for the decay products to stay in the original molecule or change their chemical character. Possible detection methods of ¹⁴N* and ⁴¹K* and their potential applications in archaeology will be discussed.      

[1]  J. Szabo, I. Carmi, D. Segal, E. Mintz, “An attempt at absolute ¹⁴C dating,“ Radiocarbon

      40/1 (1998) 77-83.