Investigating the chronostratigraphy of prominent palaeosols in Lower Austria using post-IR IRSL dating

The age of most Lower Austria loess deposits is unknown; this is especially true for Middle Pleistocene loess because there is no generally applicable dating method available. Recently it has been shown that infrared stimulated luminescence (IRSL) signals measured at elevated temperatures after an infrared (IR) stimulation are more stable than the standard IRSL signal measured at 50°C. These signals offer new opportunities to extend the datable age range by minimising or circumventing the undesirable anomalous fading correction. In this study we apply, for the first time, two post-IR IRSL single-aliquot regenerative (SAR) dating protocols to polymineral fine-grain samples from three loess/palaeosol sequences in Lower Austria. The luminescence characteristics and ages derived from these protocols are compared with the IRSL results obtained at 50°C. Recycling ratios, recuperation and dose recovery tests show that these protocols are applicable to the loess under investigation. Fading rates for the post-IR IRSL signals are significantly smaller than for the IRSL at 50°C; the differences in fading rates between post-IR IRSL at 225°C and post-IR IRSL at 290°C are less obvious. Significant fading corrections are needed for the ages derived from the IRSL signal at 50°C. From our study we conclude that the fading corrected post-IR IRSL at 225°C and the fading uncorrected post-IR IRSL at 290°C provide the best age estimates; we prefer the latter because no fading correction is apparently needed. Our data strongly suggest that the pedocomplex ‘Paudorfer Bodenbildung’ developed during marine isotope stage (MIS) 5, whereas the pedocomplex ‘Göttweiger Verlehmungszone’ is significantly older (≥ 350 ka) than has been suggested in former studies.