Erosions on the southern Tibetan Plateau:Evidence from in-situ cosmogenic nuclides^(10)Be and^(26)Al in fluvial sediments  

青藏高原南缘地表侵蚀--来自河流沉积物中宇宙成因核素^(10)Be和^(26)Al的证据

作　　者：ZHANG Xiaolong XU Sheng CUI Lifeng ZHANG Maoliang ZHAO Zhiqi LIU Congqiang 张小龙;徐胜;崔丽峰;张茂亮;赵志琦;刘丛强(Institute of Surface-Earth System Science,School of Earth System Science,Tianjin University,Tianjin 300072,China;School of Earth Science and Resources,Chang'An University,Xi’an 710054,China)

机构地区：[1]Institute of Surface-Earth System Science,School of Earth System Science,Tianjin University,Tianjin 300072,China [2]School of Earth Science and Resources,Chang'An University,Xi’an 710054,China

出　　处：《Journal of Geographical Sciences》2022年第2期333-357,共25页地理学报（英文版）

基　　金：Second Tibetan Plateau Scientific Expedition and Research(STEP)Program,No.2019QZKK0707;National Key Research and Development Program of China,No.2020YFA0607700;National Natural Science Foundation of China,No.41930863;China Seismic Experimental Site,No.2019CSES0104。

摘　　要：Investigating topographic and climatic controls on erosion at variable spatial and temporal scales is essential to our understanding of the topographic evolution of the orogen.In this work,we quantified millennial-scale erosion rates deduced from cosmogenic^(10)Be and^(26)Al concentrations in 15 fluvial sediments from the mainstream and major tributaries of the Yarlung Zangbo River draining the southern Tibetan Plateau(TP).The measured ratios of^(26)Al/^(10)Be range from 6.33±0.29 to 8.96±0.37,suggesting steady-state erosion processes.The resulted erosion rates vary from 20.60±1.79 to 154.00±13.60 m Myr-1,being spatially low in the upstream areas of the Gyaca knickpoint and high in the downstream areas.By examining the relationships between the erosion rate and topographic or climatic indices,we found that both topography and climate play significant roles in the erosion process for basins in the upstream areas of the Gyaca knickpoint.However,topography dominantly controls the erosion processes in the downstream areas of the Gyaca knickpoint,whereas variations in precipitation have only a second-order control.The marginal Himalayas and the Yarlung Zangbo River Basin(YZRB)yielded significantly higher erosion rates than the central plateau,which indicated that the landscape of the central plateau surface is remarkably stable and is being intensively consumed at its boundaries through river headward erosion.In addition,our^(10)Be erosion rates are comparable to present-day hydrologic erosion rates in most cases,suggesting either weak human activities or long-term steady-state erosion in this area.

关 键 词：in-situ^(10)Be and^(26)Al ^(26)Al/^(10)Be ratio basin-scale erosion topographic and climatic control Yarlung Zangbo River southern Tibet 

分 类 号：P512.2[天文地球—地质学] P597