Are quick equivalent doses realistic? Testing range-finder luminescence dating for water-lain and postglacial flooding sediments in NE Poland

Abstract

Raw sediment samples which are without prior lengthy laboratory preparation can be used to obtain a rough but rapid estimate of the luminescence equivalent dose, and thus of the relative age of the sediment. In this study, we tested this range-finder method on clastic sediments in NE Poland for the first time, with special focus on Pleistocene meltwater sediments generated by highly energetic glacial lake outburst floods, and the post-flooding sediments. Two datasets with known doses from standard measurements were compared to range-finder doses determined from quartz and feldspar in untreated sediments. We found statistically significant correlation between equivalent doses of (1) standard quartz optically stimulated luminescence (OSL) and range-finder feldspar infrared stimulated luminescence (IRSL) at 50 ºC, and (2) standard quartz OSL and range-finder quartz OSL in low-dose samples (<80 Gy). However, these correlations should only be considered as approximate whereby preparing more than three range-finder aliquots has the potential of yielding more accurate results. Correlation between the range-finder quartz OSL and range-finder feldspar IRSL is also significant. The rangefinder measurements can be used for approximate dose determination to preliminary assess the sediment age or as a selection tool to avoid incompletely bleached samples. The sedimentary environment and especially sediment reworking and transportation seem to influence these correlations. We consider the sediments studied here to have undergone between one and four reworking stages, and samples with repeated reworking usually represent well-bleached material for luminescence dating.