A multi-proxy approach to dose rate determination at the Kowalewo and Baranówko sites, Poland

Abstract

This study evaluates the accuracy of dose rate determination for OSL dating of aeolian sediments, focusing on the origin and variability of the internal dose rate. We compared HPGe gamma spectrometry, ICP-MS, and the μDOSE system for samples from two contrasting dune profiles in Poland: Kowalewo (fluvial-disturbed) and Baranówko (highly mature aeolian). A key finding is the identification of "radioactive" or "dirty" quartz grains, which exhibit elevated radionuclide content prior to chemical etching, significantly impacting the total annual dose. To investigate the mineralogical controls on these dose rate variations, we employed QEMSCAN and Principal Component Analysis (PCA). Our results demonstrate that the dose rate is primarily governed by microscopic inclusions of heavy minerals (e.g., zircon, apatite) and potassium-bearing phases (K-feldspars). PCA reveals that while intense aeolian transport at the Baranówko site effectively stripped the sediment of these radioactive carriers leading to a quartz-dominated, low-radioactivity matrix the Kowalewo sediments retain a complex mineralogical fingerprint. This study highlights that accounting for grain-specific micro-dosimetry and mineralogical inclusions is essential for enhancing the reliability of OSL chronologies in heterogeneous sandy deposits.