Optically stimulated luminescence dating of Late Quaternary glaciogenic sediments in the upper Hunza valley: validating the timing of glaciation and assessing dating methods

Abstract

We present a comprehensive comparison of optically stimulated luminescence (OSL) ages with cosmogenic radionuclide (CRN) ages, and the first study to validate CRN dates from boulders on moraine ridges using luminescence dates from glaciogenic sediments from associated moraines, accomplished from both direct and stratigraphic relationships between CRN and OSL sampling sites. Both quartz and K-feldspars extracted from 12 Late Quaternary glaciogenic sediments were studied using single-aliquot OSL techniques. Rapid signal saturation in preliminary additive-dose infrared-stimulated K-feldspar luminescence growth data was interpreted as evidence of insufficiently bleached latent luminescence, and these data gave rise to overestimated ages in the majority of samples. Further analysis concentrated on replicated single-aliquot regenerative-dose (SAR) measurements of quartz minerals using blue-green stimulation. The SAR sensitivity correction method repeatedly failed in two of the samples and a further sample exhibited significant thermal transfer. Nevertheless, three of the eight glacial successions in the upper Hunza valley were defined using quartz-luminescence. Although we discuss the possibility of inherited components in the CRN data, in terms of paleoclimatic interpretations both dating techniques give concordant results.