A single-aliquot luminescence dating procedure for K-feldspar based on the dose-dependent MET-pIRIR signal sensitivity

Abstract

It has been shown previously that the ‘sensitivity’ of the post-infrared infrared stimulated luminescence (post-IR IRSL or pIRIR) signal—that is, the intensity of the test dose signal (Tx)—can retain a ‘memory’ of the pre-dose received in nature, but can be reset by sunlight bleaching. Based on this observation, we describe here a single-aliquot regenerative-dose (SAR) multiple elevated temperature (MET) pIRIR dating procedure for K-feldspar that differs in one important respect from the conventional SAR MET-pIRIR procedure. Instead of using a high temperature IR bleaching step between each SAR cycle—as in the conventional procedure—our modified procedure uses a solar simulator bleach for 2 h to reset the dose-dependent pIRIR signal sensitivity before each regenerative SAR cycle. We show that the De can be obtained directly from either the Tx signal or the sensitivity-uncorrected signal (Lx) using the modified procedure. Both of these signals saturate at a higher dose than the sensitivity-corrected signal (Lx/Tx) and, hence, can be used to date older sediments than is feasible using conventional IRSL or pIRIR methods. We have tested our new procedure on 10 sediment samples from different regions of Europe (France and Italy) and Asia (China, Georgia and India), including samples with independently known ages of between ∼48 and ∼470 ka. Based on these external comparisons of age, and on internal (dose recovery) validation tests of the performance of this new pre-dose MET-pIRIR (or pMET-pIRIR) SAR procedure, we conclude that it can potentially measure natural doses of up to ∼1500 Gy in K-feldspar and produce reliable ages for Late and Middle Pleistocene sediments.