Bleaching of the post-IR IRSL signal from individual grains of K-feldspar: Implications for single-grain dating

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Abstract

Post-IR IRSL (pIRIR) signals from K-feldspar grains measured at elevated temperatures are increasingly being used for dating sediments. Unfortunately the pIRIR signal from K-feldspars bleaches more slowly than other signals (e.g. OSL from quartz) upon exposure to daylight, leading to concerns about residual signals remaining at deposition. However, earlier studies have not assessed whether the pIRIR signal bleaches at the same rate in all feldspar grains. In this study laboratory bleaching experiments have been conducted and for the first time the results show that the rate at which the pIRIR signal from individual K-feldspar grains bleach varies. To determine whether grain-to-grain variability in bleaching rate has a dominant control on equivalent dose (D e) distributions determined using single grains, analysis was undertaken on three samples with independent age control from different depositional environments (two aeolian and one glaciofluvial). The D e value determined from each grain was compared with the rate at which the pIRIR 225 signal from the grain bleaches. The bleaching rate of each grain was assessed by giving a 52 Gy dose and measuring the residual D e after bleaching for an hour in a solar simulator. There is no clear relationship between the rate at which the pIRIR 225 signal of an individual grain bleaches and the magnitude of its D e. It is concluded that variability in the bleaching rate of the pIRIR 225 signal from one grain to another does not appear to be a dominant control on single grain D e distributions.

Original languageEnglish
Pages (from-to)33-42
Number of pages10
JournalRadiation Measurements
Volume79
Early online date09 Jun 2015
DOIs
Publication statusPublished - 01 Aug 2015

Keywords

  • Bleaching rate
  • Feldspar
  • Infrared stimulated luminescence
  • Luminescence
  • Residual D values
  • Single grains
  • pIRIR

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