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20世纪80年代兴起的宇生核素暴露测年技术是目前冰川地貌研究中最为成功的测年方法之一,多数学者通常选择冰川漂砾进行暴露测年研究。然而,冰川漂砾在出露后期可能经过再次搬运造成“翻转”现象,从而影响测年结果。重建这类翻转漂砾的运动历史,对准确测定冰川地貌年代具有重要意义。青藏高原东南部的稻城古冰帽区保存了大量的古冰川遗迹,是宇生核素暴露测年研究的天然实验室。冰帽区有一被人为劈开的巨型漂砾,其内部垂直剖面上底部样品的宇生核素~(10)Be浓度高于顶部样品,推断该漂砾自初次出露之后可能发生过翻转。本文利用该漂砾顶部、底部、左右侧面的样品通过宇生核素~(10)Be暴露测年技术来重建该漂砾的运动历史。研究结果表明:该漂砾可能是由于深海氧同位素3阶段(Marine Isotope Stage,简称MIS 3)冰川作用暴露于地表,随后经过翻转直至目前状态。
One of the most successful dating methods for glacial landform research is the dating dating technique of rising concentrations of uranium exposed in the 1980s. Most scholars choose glacial boulders to conduct exposure dating. However, glacial boulders may be “flipped” after they are re-transported in the late stages of exposure, thus affecting the dating results. Reconstructing the history of such overturning boulders is of great significance for accurately determining the age of glaciers. In the southeastern part of the Qinghai-Tibet Plateau, the Ancient Ice Cap area of Daocheng has preserved a large number of ancient glacial relics and is a natural laboratory for the study of the dating of uranyl ions. There is an artificially cleaved giant boulder in the ice cap area where the concentration of ~ (10) Be at the bottom of the vertical section is higher than that of the top sample, suggesting that the boulder may have flipped after it was first exposed. In this paper, we use the samples from the top, bottom and left and right sides of the boulder to reconstruct the movement history of the boulder by using the ubiquitin ~ (10) Be exposure dating technique. The results show that the boulder may be exposed to the surface due to the marine Isotope Stage 3 (MIS 3) glaciation and then flipped to its present state.