Single‐grain K‐feldspar luminescence dating on primary and re‐deposited aeolian sediments in Mongolia

Owing to its location in the semi‐arid region of northern Central Asia, Mongolia is highly sensitive to climate change and therefore provides an excellent setting for palaeoenvironmental research. Proxy data from different sediment types are crucial for interpreting past climate changes and landscape evolution, while burial ages provide chronological frameworks for reconstructing specific periods. However, since deposits may originate from multi‐genetic process chains and sediment cascades, determining the timing of their last transportation and deposition needs a clear geomorphological analysis of the geoarchives. Optically stimulated luminescence (OSL) dating is a well‐established method in determining burial ages. However, OSL dating of sediments in Mongolia is challenging. The quartz OSL signal of sediments in Mongolia is often dim and exhibits feldspar contamination. As a result, previous studies mostly used K‐feldspar (KF) post‐IR infrared stimulated luminescence (pIRIR) signals for luminescence dating. However, KF pIRIR signals bleach much slower than quartz OSL signals, and insufficient bleaching of pIRIR signals prior to deposition might result in burial age overestimation, especially for water‐lain sediments where exposure to sunlight is often limited. Single‐grain (SG) dating of KF could be a useful tool in this case, as it can derive reliable burial ages for partially bleached samples by applying a minimum age model. Hitherto, the reliability of KF SG dating has not been sufficiently studied on Mongolian sediments. In this study, we performed both KF SG dating and multi‐grain dating with the pIRIR 150 signal (pIRIR signal at 150 °C) on 30 sediment samples collected from 17 profiles across Mongolia, together with 14 C dating of 12 samples of organic sediment and plant material. KF SG dating results show that only the five samples of primary aeolian sediment were well bleached prior to deposition, while all of the 25 samples of remobilized, transported and redeposited sediment (e.g. by fluvial, alluvial and colluvial processes) were partially bleached during the final transport process, thus showing positively skewed distributions of SG equivalent doses. The KF ages obtained with multi‐grain aliquots significantly overestimated the true burial ages and often showed age reversals. KF SG ages obtained by applying a minimum age model were consistent with radiocarbon ages and followed the stratigraphic order. Our study demonstrates that KF SG dating is the most suitable luminescence dating method for re‐deposited aeolian sediments in Mongolia.