Cosmogenic nuclide exposure dating is one of the most intensively applied dating methods with which to study glacial geomorphology. Glacial erratics have been the major dating objective in many studies. Some research has proposed that glacial erratics may undergo rollover and re-transportation during the late exposure stage, which can affect the dating results. However, there is no direct evidence to confirm this possibility. In this study, we collected seven samples from a vertical section inside a glacial erratic in the paleo-Daocheng ice cap in the southeastern Tibetan Plateau, measuring their contents of the cosmogenic nuclides ¹⁰Be and ²⁶Al. The results show that from the top to the bottom, the concentrations of ¹⁰Be were (1.21 ± 0.05) × 10⁶, (1.00 ± 0.02) × 10⁶, (0.88 ± 0.03) × 10⁶, (0.77 ± 0.02) × 10⁶, (0.75 ± 0.03) × 10⁶, (0.95 ± 0.03) × 10⁶ and (1.46 ± 0.04) × 10⁶ atoms/g. The ¹⁰Be concentrations decreased from (1.21 ± 0.05) × 10⁶ atoms/g to (0.75 ± 0.03) × 10⁶ atoms/g and then increased to (1.46 ± 0.04) × 10⁶ atoms/g, which is not consistent with the theoretical prediction of a gradual decrease. This phenomenon indicates that the glacial erratic may have rolled over at least once. The lower surface of the erratic could have been on top at some time in the past. Therefore, its exposure age was greater than the exposure age that was expected, based on its current orientation. This study provides numerical evidence for an erratic rollover event.

中文翻译：

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10Be 和 26Al 浓度变化揭示了冰川不稳定翻滚的证据

宇宙成因核素暴露测年是研究冰川地貌学应用最广泛的测年方法之一。在许多研究中，冰川不稳定一直是主要的测年目标。一些研究提出，冰川游走物在暴露后期可能会发生翻滚和重新迁移，从而影响测年结果。但是，没有直接证据证实这种可能性。在这项研究中，我们从青藏高原东南部古稻城冰盖的冰川飘忽不定内部垂直剖面采集了 7 个样本，测量了它们的宇宙成因核素¹⁰ Be 和²⁶ Al 的含量。结果表明，从上到下，¹⁰ Be的浓度为（1.21±0.05）×10 ⁶, (1.00 ± 0.02) × 10 ⁶ , (0.88 ± 0.03) × 10 ⁶ , (0.77 ± 0.02) × 10 ⁶ , (0.75 ± 0.03) × 10 ⁶ , (0.95 ± 0.03) × 10 ⁶和 (1.46 ± 0.04 ) × 10 ⁶原子/克。10 Be浓度从(1.21±0.05)×10 ^6原子/g下降到(0.75±0.03)×10 ⁶原子/g，然后增加到(1.46±0.04)×10 ⁶原子/克，这与逐渐减少的理论预测不一致。这种现象表明冰川不稳定可能至少翻滚过一次。不稳定的下表面可能在过去的某个时间位于顶部。因此，其暴露年龄大于基于其当前方向的预期暴露年龄。这项研究为不稳定的翻车事件提供了数字证据。