Single-grain K-feldspar post-IR IRSL dating of glaciofluvial sediments of Guxiang Glaciation in SE Tibetan Plateau

Abstract

The Guxiang Glaciation, a key reference for classifying late Quaternary glaciations on the Tibetan Plateau, has been dated to MIS 6 using cosmogenic ¹⁰Be exposure dating of two boulders. However, additional dating methods are needed to evaluate and improve its chronology. In this study, we used the post-infrared infrared stimulated luminescence (post-IR IRSL) signal at 225 °C from single K-feldspar grains to date a lateral moraine corresponding to the Guxiang Glaciation in the Bodui Zangbo Valley, southeastern Tibetan Plateau. Six samples from glaciofluvial sand lenses interbedded within the moraine were analyzed. The L_nT_n method was utilized for D_e determination to avoid truncation in D_e distribution and age underestimation. A common standardized growth curve (SGC) was established for all samples, and the least-squares (LS)-normalized L_n/T_n values of the brightest grains were selected for L_n/T_n and D_e estimation using the central age model (CAM). Using one fading-correction model, the post-IR IRSL ages (159 ± 9 ka to 181 ± 11 ka, average value of 173 ± 4 ka) fall within the expected MIS 6 interval and align with previous ¹⁰Be exposure ages. However, the ages are close to the limit of the method, and a different model for correcting fading suggests a much older age (average 308 ± 27 ka). This study reveals both the potential and challenges of single-grain K-feldspar luminescence dating as a means to establish chronological control for glaciations beyond the last glacial period on the Tibetan Plateau.