Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K-feldspar

Infrared stimulated luminescence (IRSL) dating of K-feldspars may be an alternative to quartz optically stimulated luminescence (OSL) dating when the quartz OSL signal is too close to saturation or when the quartz luminescence characteristics are unsuitable. In this paper, Eemian (MIS 5e) coastal marine sands exposed in a cliff section on the coast of southern Jutland (Denmark) are used to test the accuracy and precision of IRSL dating using K-feldspars. This material has been used previously to test quartz OSL dating (Murray & Funder 2003): a small systematic underestimation of < 10% compared to the expected age of similar to 130 ka was reported. In our study, a single-aliquot regenerative-dose (SAR) IRSL protocol is used to determine values of equivalent dose (D(e)) and the corresponding fading rates (g values). A significant age underestimation (of up to similar to 35%) is observed; this is attributed to anomalous fading. Using a single site-average fading rate of 3.66 +/- 0.09%/decade to correct the IRSL ages for all samples provides good agreement between the average fading-corrected K-feldspar age (119 +/- 6 ka) and the independent age control (132-125 ka). This is despite the reservations of Huntley & Lamothe (2001) that their fading correction method is not expected to work on samples older than similar to 20-50 ka. This fading-corrected feldspar result is not significantly different from the overall revised quartz age (114 +/- 7 ka) also presented here. We conclude that fading-corrected IRSL ages measured using K-feldspar may be both precise and accurate over a greater age range than might be otherwise expected.