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

IF 1.7 2区地球科学 Q3 GEOGRAPHY, PHYSICAL Quaternary Geochronology Pub Date : 2024-05-22 DOI:10.1016/j.quageo.2024.101547

Kunmei Yang , Xianjiao Ou , Yang Li , Geraint Jenkins , Pan Yao , Daobin Tang , Yantian Xu , Jinming Xie , Lanhua Zeng , Xiangjun Liu

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Abstract

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-IR₅₀ IRSL₂₂₅ single aliquot regenerative dose (SAR) protocol was applied to measure the luminescence signal from rock slices. The IRSL₅₀ 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.

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对青藏高原东部理塘河源头地区（孔隆洛河谷）冰碛中埋藏的鹅卵石进行发光测年

冰碛沉积物很难使用传统的发光技术来确定其年代，尤其是地貌中没有冰川流砂透镜体的沉积物。最近开发的岩石表面发光埋藏测年法显示出了制约异质冰川淤积沉积物的潜力。然而，从冰碛沉积物中获得的鹅卵石的发光测年法是否具有更广泛的适用性还需要检验。本研究从青藏高原东部理塘河源头地区末次冰期冰碛系列不同世代的末端冰碛中采集了 31 块埋藏的花岗岩鹅卵石。从两块冰碛的山脊上采集的八块巨石产生了八个宇宙成因核素 10Be 暴露年龄，以提供外部年龄对照。采用 IRSL225 后 IR50 单等分再生剂量（SAR）方案测量岩石切片的发光信号。23 块鹅卵石的 IRSL50 Ln/Tn 深度剖面显示出表面年龄高原（高达 12 毫米），表明这些材料在沉积前已被充分漂白。漂白前沿的深度在同一矿床的不同鹅卵石之间存在差异。我们采用了三种不同的方法来观察和纠正存在的任何异常褪色现象。我们观察到从同一冰碛沉积中采集的不同鹅卵石的年龄一致，这说明我们所选地点的鹅卵石具有可重复性。埋藏卵石的发光年龄（15.5 ± 2.1 ka 至 20.0 ± 1.6 ka）与地貌关系和 10Be 暴露年龄一致。特别是其中一个冰碛的鹅卵石年龄（20.0 ± 1.6 ka）与同一冰碛的巨石的独立 10Be 暴露年龄（18.6 ± 1.2 ka）一致。这项研究证明了利用鹅卵石对冰碛沉积物进行发光测年的适用性，并为深入了解青藏高原东部最后一次冰川作用提供了依据。

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来源期刊

Quaternary Geochronology 地学-地球化学与地球物理

CiteScore

4.40

自引率

22.20%

发文量

130

审稿时长

20 weeks

期刊介绍： Quaternary Geochronology is an international journal devoted to the publication of the highest-quality, peer-reviewed articles on all aspects of dating methods applicable to the Quaternary Period - the last 2.6 million years of Earth history. Reliable ages are fundamental to place changes in climates, landscapes, flora and fauna - including the evolution and ecological impact of humans - in their correct temporal sequence, and to understand the tempo and mode of geological and biological processes.