Abstract
Among dating methods that can be applied to Quaternary sediments, quartz OSL (Optically Stimulated Luminescence) dating has been used in various environments because quartz, the target mineral for dating, are ubiquitous. Recently, for samples older than datable limit of quartz OSL dating (ca. similar to 10 ka), K-feldspar IRSL (InfraRed Stimulated Luminescence) signals are widely applied. In this paper, we aim to examine the bleaching characteristics of K-feldspar pIRIR(225) signal and the reliability of the K-feldspar pIRIR(225) age results. K-feldspar pIRIR(225) signals stimulated with solar simulator show slower bleaching than those of quartz OSL and K-feldspar IR50 signal. This indicates that the K-feldspar pIRIR(225) ages are likely to overestimate the depositional ages due to slow bleaching at deposition. K-feldspar pIRIR(225) dating performed on a modern flood deposit was, however, as low as 8.8 +/- 0.6 Gy. Although K-feldspar pIRIR(225) ages for five samples collected from terrestrial alluvial fan dep