气候变化领域集成服务门户(CCPortal): Reconstructing the incision of the Lancang River (Upper Mekong) in southeastern Tibet below its prominent knickzone using fluvial terraces and transient tributary profiles

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DOI	10.1016/j.geomorph.2020.107551
	Reconstructing the incision of the Lancang River (Upper Mekong) in southeastern Tibet below its prominent knickzone using fluvial terraces and transient tributary profiles
	Zhang J.; Yang H.; Liu-Zeng J.; Ge Y.; Wang W.; Yao W.; Xu S.
发表日期	2021
ISSN	0169555X
卷号	376
英文摘要	The Lancang River (Upper Mekong) is a key large river in Asia with a prominent knickzone over 500 km distance (27.5-30.7°N), as it descends the southeastern margin of the Tibetan Plateau. To explore the role of tectonics in regulating the river downcutting at regional and local scales, we reconstructed the rate and spatial pattern of incision within and below the knickzone. We combined the investigation of fluvial terraces with tributary river profile analysis for a 300-km reach near Yunlong below the knickzone (25–27.5°N). We conducted field mapping and dating of strath terraces at the heights of 60–380 m above the trunk river. The overlying terrace deposits comprise fluvial conglomerates and overbank sands as well as tributary alluvial fan conglomerates. K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating results suggest terrace formation during the Middle Pleistocene and the incision rate varying at <0.59–0.22 mm/yr. The river profiles of most tributaries in the study area are in a transient state with a knickpoint separating an upstream relict graded profile and a downstream steepened reach. These tributary profiles suggest river incision of ~50–1800 m, showing a spatial trend of increase towards the north. Knickpoint elevation and channel steepness of tributaries show a similar spatial pattern of northward increase. We suggest that the spatial variation in river incision along the Lancang River near Yunlong is likely to have been regulated by differential rock uplift in southeastern Tibet. Using the K-feldspar pIRIR dating method, we rectified the incision rate within the knickzone to vary at <0.63–0.28 mm/yr. New dating results thus suggest that terrace-derived incision rates along the Lancang River are similar to regional erosion rates on million-year and millennial time scales in terms of magnitude and spatial pattern. Coupled erosion rates on various time scales along the Lancang River and spatial pattern of river incision near Yunlong supports a primary role of tectonic forcing in shaping the southeastern Tibetan landscape. © 2020 Elsevier B.V.
英文关键词	Fluvial terrace; K-feldspar pIRIR dating; River incision; River profile analysis; Southeastern Tibet
语种	英语
scopus关键词	Geomorphology
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/158272
作者单位	State Key Laboratory of Earthquake Dynamics; Institute of Geology; China Earthquake Administration; Beijing; 100029; China; Institute of Surface-Earth System Science; Tianjin University; Tianjin; 300354; China
推荐引用方式 GB/T 7714	Zhang J.,Yang H.,Liu-Zeng J.,et al. Reconstructing the incision of the Lancang River (Upper Mekong) in southeastern Tibet below its prominent knickzone using fluvial terraces and transient tributary profiles[J],2021,376.
APA	Zhang J..,Yang H..,Liu-Zeng J..,Ge Y..,Wang W..,...&Xu S..(2021).Reconstructing the incision of the Lancang River (Upper Mekong) in southeastern Tibet below its prominent knickzone using fluvial terraces and transient tributary profiles.,376.
MLA	Zhang J.,et al."Reconstructing the incision of the Lancang River (Upper Mekong) in southeastern Tibet below its prominent knickzone using fluvial terraces and transient tributary profiles".376(2021).