The timing of the penultimate glaciation in the northern Alpine Foreland: new insights from luminescence dating

Only minimal age constraints are as yet available concerning the timing of the penultimate glaciation in the European Alps. Therefore, this study presents the results of different luminescence dating approaches, revealing the depositional ages of glaciofluvial sediments deposited in the Austrian Northern Alpine Foreland during the penultimate glaciation. To establish a robust numerical chronology we investigated 18 samples of mostly glaciofluvial origin using the optically stimulated luminescence (OSL) signal of quartz and the post-infrared infrared (pIRIR) stimulated luminescence signal at 225 °C of potassium rich feldspar for the grain size of 100-200 μm. By comparing the results gained from both analytical approaches, it was possible to discern between samples that were well bleached prior to deposition and samples for which the luminescence signals were not properly reset. The ages presented in this study suggest that the deposition of proglacial outwash deposits in the northern Alpine foreland associated with the penultimate glaciation is time equivalent with marine isotope stage (MIS) 6. Furthermore, our results imply relatively rapid ice decay in late MIS 6 towards termination 2, which is consistent with previous studies dealing with the penultimate glaciation in the circum-alpine region. Although the dating results allow to chronologically discern between glacial and interglacial periods, a finer resolution on a stadial/interstadial level cannot unfortunately be obtained by the current state-of-the-art methods of luminescence dating as applied in this study.