Single-grain dating of young sediments using the pIRIR signal from feldspar

Abstract

In this article we test for the first time the potential of single-grains of K-rich feldspar to date well-bleached and poorly bleached sediments using a post-IR IRSL (pIRIR) protocol. We measure natural dose distributions using K-rich feldspars from four coastal samples applying the pIRIR protocol with a preheat of 200°C and a pIRIR stimulation temperature of 180°C; each sample had an independent age control obtained from quartz OSL and radiocarbon dating. We also analyse single-grain dose distributions of “zero-dose” and γ-irradiated samples to determine thermal transfer/residual doses and the intrinsic sources of variability of pIRIR single-grain measurements, respectively. Based on these experiments, we conclude that thermal transfer/residual dose give rise to an offset of ∼0.6Gy in these samples and that the uncertainty assigned to individual pIRIR single-grain dose estimates cannot be smaller than 16.5%.The analysis of the well-bleached samples shows that only the brightest 30% of the grains give pIRIR single-grain ages in agreement with the age control; this effect may arise from the suggested correlation between blue emission and potassium content of individual grains. Comparison of single-grain quartz and feldspar dose distributions from the poorly bleached samples shows that quartz is relatively better bleached; nevertheless, selection of a reliable ‘minimum’ feldspar dose was achieved using two different statistical models.