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Testing the suitability of dim sedimentary quartz from northern Switzerland for OSL burial dose estimation

Trauerstein M., Lowick S. E., Preusser F., Veit H.

Geochronometria

2017

Vol. 44, no. 1

66--76

We investigate the suitability of sedimentary quartz associated with former glacial advances in northern Switzerland to provide reliable burial dose estimates using Optically Stimulated Luminescence (OSL). Previous studies on northern alpine quartz show that its signal characteristics can be poor and potentially problematic. We analyse quartz signals of small aliquots, which reveal the presence of a prominent medium or slow component in the initial part of some signals. Nonetheless, rejection of aliquots with unfavourable signal composition does not alter the burial dose estimates, but significantly reduces the data set for De determination. Signal lifetimes from isothermal decay measurements cover a wide range of values, yet the lowest lifetimes are high enough to guarantee a reliable burial dose estimate for samples of < 400 ka. Comparison of small aliquot and single grain burial dose distributions reveals that signal averaging masks partial bleaching in some of the samples. We therefore strongly recommend single grain measurements for samples from this setting and area, in order to exclude age overestimation due to partial bleaching.

Performance of different luminescence approaches for the dating of known-age glaciofluvial deposits from northern Switzerland

Gaar D., Lowick S. E., Preusser F.

Geochronometria

2014

Vol. 41, no. 1

65--80

Luminescence properties of two samples taken from sand lenses in proglacial outwash de-posits of a piedmont glacier that reached the Swiss midlands during the Last Glacial Maximum are investigated in detail. Deconvolution of CW-OSL decay curves shows that the fast component domi-nates the OSL signal of quartz. The chemistry of single feldspar grains, in particular the K content in different grains, is determined using wavelength dispersive spectrometry (electron microprobe), re-vealing an average 12.9 wt.% K of the grains contributing to the IRSL signal. De distributions are in-vestigated in order to gain insights into partial bleaching, and agreement is found for quartz OSL and feldspar IR50 and pIRIR225 ages for small aliquots and single grains when applying the Minimum Age Model. These ages are also consistent with independent age control. For one sample, ages determined using the Central Age Model result in highly overestimated ages for both feldspar and quartz.