Optical dating of potassium feldspar using far-red ( λ>665 nm) IRSL emissions: a comparative study using fluvial sediments from the Loire River, France

• Published in: Quaternary science reviews 2003-05, Vol.22 (10), p.1093-1098
• Main Authors: Arnold, Lee, Stokes, Stephen, Bailey, Richard, Fattahi, Morteza, Colls, Alison, Tucker, Greg
• Format: Article
• Language: English
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/S0277-3791(03)00033-7

UV-blue emissions from feldspars have often proved to be unacceptable dosimeters for age estimation given the intrinsic problem of anomalous fading. The potential of exploiting the far-red (>665 nm) IRSL emissions from potassium feldspars as a means of avoiding the malign effects of anomalous fading has recently been proposed (Studies on red thermoluminescence and infrared stimulated luminescence. Unpublished D.Phil Thesis, University of Oxford, 2001). While that research demonstrated that it was possible to detect the far-red signal in the coarse grain feldspar samples studied, it did not present any empirical data for actual geological samples with or without independent age control. The purpose of the present paper is to expand on the work of Fattahi (2001) by undertaking a direct comparison of SAR D e's and corresponding optical ages for a suite of Holocene through Late Pleistocene fluvial terrace deposits from the upper reaches of the Loire River, France. Here we describe the behaviour of the far-red emissions for these samples and present some initial dating results. The far-red IRSL emission ages obtained are compared to UV-blue IRSL emission ages for the fluvial samples and to corresponding optical ages previously generated on quartz fractions from the same samples. Initial results are promising but show some inconsistencies. Basic experiments demonstrate that this is not attributable to insufficient sensitivity correction by SAR in the far-red emissions, neither was anomalous fading detected in either the far-red or UV-blue emissions over short storage times. It is suggested that refinement of pre-treatment and measurement conditions should enable more successful dating of feldspars with far-red emissions and that further research on the potentially stable far-red signal is necessary.