Cosmogenic nuclide burial ages and provenance of the Xigeda paleo-lake: Implications for evolution of the Middle Yangtze River
Cosmogenic nuclide burial ages and provenance of the Xigeda paleo-lake: Implications for evolution of the Middle Yangtze River
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DOI：
10.1016/j.epsl.2008.12.003
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发表时间：
2009-02
影响因子：
5.3
通讯作者：
P. Kong;D. Granger;Fu-Yuan Wu;M. Caffee;Ya-jun Wang;Xitao Zhao;Yong Zheng
中科院分区：
文献类型：
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作者：
P. Kong;D. Granger;Fu-Yuan Wu;M. Caffee;Ya-jun Wang;Xitao Zhao;Yong Zheng
长江中游沿着广泛分布着数百米厚的湖相沉积。这些沉积物的分布表明，一次事件阻塞了河流，形成了一个湖，东西长160 km，南北长110 km，深度≥500 m。利用宇宙成因核素10 Be和26 Al测定了湖泊沉积物和沉积物下河流砾石的埋藏时间。我们的研究结果表明，这些沉积物的沉积年龄为1.34和1.58马之间。通过对与古湖泊形成有关的湖相沉积物和河流砂中锆石U-Pb年龄分布的研究，发现其物源来自长江上游和雅砻江。这些沉积物含有地质指纹，可以识别湖相沉积物和河流砂的源区。研究结果支持了古湖泊形成前长江中游的逆转。我们推测，阻塞了原本向南流动的地质事件是第四纪早期开始的大理断裂系中澄海断裂的侧向运动。水最终穿过溢洪道流向东部。
Hundred-meter-thick lacustrine sediments are widespread along the Middle Yangtze River. The distribution of these sediments suggests that an event blocked the river, forming a lake stretching 160 km from east to west and 110 km north to south, with a depth of ≥500 m. Using the cosmogenic nuclides10Be and26Al we have dated the time of burial of the lacustrine sediments and fluvial gravels beneath the sediments. Our results indicate a deposition age for these sediments between 1.34 and 1.58 Ma. Studies of zircon U–Pb age distributions within lacustrine sediments and fluvial sands related to the paleo-lake formation show diverse provenances from the upper Yangtze River and Yalong River, a major tributary of the Yangtze River. These deposits contain geologic fingerprints that allow identification of the source region of the lacustrine deposits and fluvial sands. Our results support the reversal of the Middle Yangtze River before the paleo-lake formation. We hypothesize that the geologic event that dammed the originally southward flow was the lateral movement of Chenghai fault in the Dali fault system initiated in early Quaternary. Water eventually cut through the spillway and flowed to the east.