Cosmogenic 10Be and 26Al exposure dating of Nam Co lake terraces since MIS 5, southern Tibetan Plateau
Cosmogenic 10Be and 26Al exposure dating of Nam Co lake terraces since MIS 5, southern Tibetan Plateau
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DOI：
10.1016/j.quascirev.2020.106175
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发表时间：
2020-03
影响因子：
4
通讯作者：
Jie Zhou;Weijian Zhou;G. Dong;Ya-Mei Hou;F. Xian;Li Zhang;L. Tang;Guoqing Zhao;Yunchong Fu-Yunchon
中科院分区：
文献类型：
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作者：
Jie Zhou;Weijian Zhou;G. Dong;Ya-Mei Hou;F. Xian;Li Zhang;L. Tang;Guoqing Zhao;Yunchong Fu-Yunchon
湖泊古海岸线可用于重建湖泊水位波动，作为气候变化的敏感指标。青藏高原（TP）是中国湖泊面积比例最高的地区，过去剧烈的湖泊水位变化导致形成了众多的遗迹岸线。在这里，我们展示了位于青藏高原南部纳木错以北的七个湖泊阶地中的五个的 2410Be 和 26Al 暴露年龄。以阶地为标志的四个高位（T7、T6、T5和T4）的年龄分别为81.5±9.0ka、33.6±1.9ka、19.9±1.9ka和15.2±0.4ka。地形最高的阶地 T7 与印度夏季风 (ISM) 增强的时期相关，并支持高原上 MIS 5 最大湖泊扩张，而不是 MIS 3。两个较低阶地（T5 和 T4）的年龄可能对应于融水脉冲 (MWP) 事件。我们还评估了湖泊阶地 10Be 暴露年龄的地质过程中不同可能的不确定性来源。阶地暴露后的地下侵蚀对古代高阶地（例如> 80 ka）的10Be暴露年龄影响最为显着，而对于相对较低和年轻的阶地（例如< 15 ka），来自先前暴露的10Be暴露年龄和浅水、海滩或距骨的部分遮挡是最重要的10Be暴露年龄地质源误差。
Lake paleo-shorelines can be used to reconstruct lake level fluctuations, which serve as sensitive indicators of climate change. The Tibetan Plateau (TP) contains the highest areal proportion of lakes in China, and dramatic past lake level changes have led to the formation of numerous relict shorelines. Here, we present 2410Be and26Al exposure-ages for five of seven lake terraces situated north of Nam Co, on the southern TP. The ages of four high stands marked by terraces (T7, T6, T5, and T4) are 81.5 ± 9.0 ka, 33.6 ± 1.9 ka, 19.9 ± 1.9 ka, and 15.2 ± 0.4 ka. The topographically highest terrace, T7, correlates with periods of enhanced Indian summer monsoon (ISM) and supports an MIS 5 maximum lake expansion on the TP, as opposed to MIS 3. Ages of two lower terraces (T5 and T4) possibly correspond to Melt Water Pulse (MWP) events. We also evaluate different possible sources of uncertainty from geologic processes on10Be exposure ages of lake terraces. Subaerial erosion following terrace exposure has the most significant influence on10Be exposure ages on ancient high terraces (for example > 80 ka), while inherited10Be from prior exposure and partial shielding by shallow water, beach or talus are the most important geological source error of10Be exposure ages for relatively low and young terraces (for example < 15 ka).