Anomalous fading: a reply to the comment by Huntley on "Isochron measurements of naturally irradiated K-feldspar grains"

We are pleased that Huntley (this issue) has put forward another explanation for the data that we obtained when we measured the equivalent doses (De) of potassium (K) feldspar grains of different diameters using their infrared stimulated luminescence (IRSL) signals (Li et al., 2007). We also measured the fading rates for the IRSL signals from grains of different size and concluded that the fading rates were independent of grain size. Huntley is concerned that the fading rates (g-values) that we obtained had relatively large errors and that these could have masked any minor differences in the g-values; a small systematic shift in g-value with grain size could result in the observed differences in the ages that we obtained from the De values. Based on his calculations, he suggested that a 0.3%/decade systematic difference in g-value with grain size could explain the age differences seen in our data.