Residual luminescence signals in modern coastal sediments

Abstract

Modern sediments from coastal and near-coastal environments in England and Wales had their equivalent doses (EDs) determined using single-aliquot additive-dose infra-red stimulated luminescence (IRSL). Certain samples were also investigated using multiple-aliquot methods for IRSL, green light stimulated luminescence (GLSL) and thermoluminescence (TL), and also single-aliquot GLSL. Only one modern sample had its IRSL signal reduced to give a zero ED; those which had been deposited through turbid water columns had significant signal remaining for all stimulation methods, although the GLSL and IRSL EDs were lower than the TL. Analogous buried samples were also dated and findings were compared with the available age control and the modern results. Where a TL as well as an IRSL ED was obtained for one such sample, it was found to be considerably higher, suggesting that the bleaching environment had been poor. An unbleached residual signal in these samples could not be detected, however, and the dates reflected the age control. The selection of a water content for use in dating was found to be critical in environments with such naturally high and variable water contents.