On the calibration of fission-track annealing models

To obtain thermal histories from fission track length data, the rates at which track lengths are reduced must be estimated. The usual method is to use empirical equations calibrated via laboratory analogues. A major concern is the extrapolation of the equations to predict temperatures on the geological time scale, which is far outside the range of the calibration data. Using objective statistical criteria, it is shown that the inclusion of geological data from age standards and deep boreholes is an important measure to ensure that model predictions of geological annealing rates are at least close to being correct. It is shown that high-temperature geological data should be the preferential target in the search for new field evidence. A discussion on the use and limitations of geological data and their consequences is presented.