Evidence of Glacial Erratic Rollover Revealed by 10Be and 26Al Concentration Variations
Evidence of Glacial Erratic Rollover Revealed by 10Be and 26Al Concentration Variations
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DOI：
10.1111/1755-6724.14685
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发表时间：
2021-03
期刊：
影响因子：
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通讯作者：
Zhigang Zhang;Jian Wang;Xiaobin Xu;Zhiyang Chang;Haitao Cui;Zhong Liang;Xia Chen;Zhiyuan Shang
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文献类型：
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作者：
Zhigang Zhang;Jian Wang;Xiaobin Xu;Zhiyang Chang;Haitao Cui;Zhong Liang;Xia Chen;Zhiyuan Shang
宇宙成因核素暴露测年是研究冰川地貌学中应用最广泛的测年方法之一。冰川不稳定一直是许多研究的主要测年目标。一些研究提出，冰川不稳定因素在暴露后期可能会发生翻转和重新运输，从而影响测年结果。然而，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冰川飘忽不定内部的垂直剖面采集了七个样品，测量了它们的宇宙成因核素 10Be 和 26Al 含量。结果表明，从上到下， 10Be 浓度依次为（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。 0.03）×106和（1.46±0.04）×106原子/克。 10Be浓度从(1.21±0.05)×106atoms/g下降到(0.75±0.03)×106atoms/g,然后增加到(1.46±0.04)×106atoms/g,这与逐渐下降的理论预测不一致。这一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，它的暴露年龄大于根据其当前方向所预期的暴露年龄。这项研究为不稳定的侧翻事件提供了数值证据。
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.