Discovery of Outburst Deposits Induced by the Xuelongnang Paleolandslide-Dammed Lake in the Upper Jinsha River, China and Its Environmental and Hazard Significance
doi: 10.14027/j.cnki.cjxb.2015.02.007
- Received Date: 2014-03-04
- Rev Recd Date: 2014-06-16
- Publish Date: 2015-04-10
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Key words:
- landslide-dammed lake /
- dam break-outburst sediments /
- sedimentary features /
- ancient flood /
- the upper Jinsha River
Abstract: A distinct damming incident occurred at the prehistoric period(Late Holocene) in the upper Jinsha River in the Mangkang County, Xizang province, China. The volume of the dammed lake is about 3.1×108 m3. The dammed lake breached and caused a big outburst flood at about 1 117 A.D. We can infer that the paleoseismics induced major landslide may be the direct cause triggering the river damming. In the range between the downstream side of the ancient dam body to its downstream 3.5 km, abundance of diamicton consisting of gravels, sands and minor silts and clays was discovered. The sedimental structure of the dam break-outburst sediments includes gravel support-stacked structure, gravel imbricate structure and matrix structure, and so on. Besides, it has a special sedimental structure: rhythmites interbedded structure composed of coarser gravel layer and finer sand and gravel layer, no sand lens are formed in the layers. This special structure can be an important origin criteria of the dam break-outburst sediments. Based on back analysis using the hydraulic model, the average flow rate velocity of the outburst flood is 7.48 m/s and the maximum peak discharge is 10 786 m3/s. The research on the sedimentary features and its environment of the dam break-outburst sediments can not only be served to help revealing the process and mechanism of ancient flood incidents, but also be significant of knowing the environmetal evolution in the upper Jinsha River area.
Citation: | CHEN Jian, CUI ZhiJiu. Discovery of Outburst Deposits Induced by the Xuelongnang Paleolandslide-Dammed Lake in the Upper Jinsha River, China and Its Environmental and Hazard Significance[J]. Acta Sedimentologica Sinica, 2015, 33(2): 275-284. doi: 10.14027/j.cnki.cjxb.2015.02.007 |