Luminescence dating of cobbles buried in moraines from the source area of the Litang River (Konglongluo Valley), eastern Tibetan Plateau.

Moraine deposits are difficult to date using conventional luminescence techniques, especially such deposits without glaciofluvial sand lenses incorporated within the feature. Recently developed rock surface luminescence burial dating has shown the potential for constraining heterogeneous glacial till sediments. However, the wider applicability of the luminescence dating of cobbles obtained from moraine deposits needs to be tested. Thirty-one buried granite cobbles from different generations of terminal moraines of the last deglaciation moraine series in the source area of the Litang River, eastern Tibetan Plateau, were collected. Eight cosmogenic nuclide ¹⁰Be exposure ages were generated from eight boulders obtained from the ridges of two moraines, to provide an external age control. A post-IR 50 IRSL 225 single aliquot regenerative dose (SAR) protocol was applied to measure the luminescence signal from rock slices. The IRSL 50 L n /T n -depth profiles from 23 cobbles showing surface age plateaus (up to 12 mm), indicating that the material was well-bleached prior to deposition. The depth of the bleaching front is variable between individual cobbles from the same deposit. Three distinct methods were employed to observe and correct for any anomalous fading present. We observe age agreement from different cobbles collected from the same moraine deposits, illustrating the reproducibility at our selected locations. The luminescence ages of burial cobbles (15.5 ± 2.1 ka to 20.0 ± 1.6 ka) align with geomorphic relationships and ¹⁰Be exposure ages. Particularly, the age of cobbles from one of the moraines (20.0 ± 1.6 ka) is consistent with independent ¹⁰Be exposure ages (18.6 ± 1.2 ka) of boulders from the same moraine. This study demonstrates the applicability of the luminescence dating of moraine deposits, using cobbles, and provides deeper insights of the last deglaciation in the eastern Tibetan Plateau. • Rock surface luminescence dating of the last deglaciation moraines from east Tibet. • 74% of L n /T n -depth profiles from 31 granite cobbles indicate well bleaching. • Post-IR 50 IRSL 225 protocol to measure D e and three methods to correct fading. • NLS corrected IRSL 50 ages agree with independent ¹⁰Be exposure age control. [ABSTRACT FROM AUTHOR]