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青藏高原东缘具有青藏高原地貌、龙门山高山地貌和山前冲积平原三个一级地貌单元 ,本文以岷江作为切入点 ,研究了该地区河流下蚀速率与山脉的隆升作用之间的相互关系。在建立岷江阶地序列的基础上 ,利用阶地高程和热释光年代学测年资料分别定量计算了岷江在川西高原、龙门山和成都盆地的下蚀速率 ,结果表明岷江各河段的下蚀速率明显不同 ,分别为 1.0 7～ 1.6 1mm / a、1.81m m/ a和 0 .5 9mm / a;在龙门山地区岷江的下蚀速率最高 ,约为川西高原地区的 1.5倍 ,约为成都平原地区的 3倍 ;而同一河段不同时期岷江的下蚀速率基本是连续的 ,具有很好的线性关系 ,可作为该河段整个河谷的下蚀速率。基于龙门山的表面隆升速率 (0 .3～ 0 .4 mm / a) ,在约束局部侵蚀基准面和气候变化对阶地形成的控制作用的基础上 ,本文建立了青藏高原东缘岷江下蚀速率与龙门山表面隆升速率之间的线性关系 ,结果表明河流下蚀速率约为山脉表面隆升速率的 5倍。根据龙门山表面在隆升速率和下切速率等方面均大于川西高原 ,并结合龙门山活动构造以走滑作用为主 ,笔者认为青藏高原东缘的边缘山脉以剥蚀隆升为主 ,兼有构造隆升作用。最后 ,根据岷江最大切割深度所需的时间 (3.4 8Ma)和成都盆地最古老的岷江冲积扇大邑砾岩的时间 (3.6 Ma
The eastern edge of the Qinghai-Tibet Plateau has three landform units: the Qinghai-Tibet Plateau, the Longmenshan alpine landform and the piedmont alluvial plain. Taking the Minjiang River as an example, this paper studied the relationship between the rate of eroded rivers and the uplift of the mountains relationship. Based on the sequence of the Minjiang River terraces, the erosional rates of the Minjiang River in the western Sichuan Plateau, the Longmen Mountains and the Chengdu basin are quantitatively calculated by using terrace elevation and thermoluminescence chronological data. The results show that the erosion rates The difference between them is 1.07-1.61mm / a, 1.81mm / a and 0.59mm / a, respectively. The erosion rate of the Minjiang River in Longmenshan area is the highest, about 1.5 times that of the western Sichuan plateau, about the same as the Chengdu Plain The erosion rate of the Minjiang River in the same section is basically continuous and has a good linear relationship, which can be used as the erosion rate of the entire river valley. Based on the Longmenshan surface uplift rate (0.3 ~ 0.4 mm / a), on the basis of restraining the local erosion datum and controlling the formation of terrains due to climate change, And the Longmen Shan surface uplift rate of the linear relationship between the results show that the rate of erosion down the river about the mountain uplift rate of 5 times. According to the fact that the surface of Longmenshan is larger than the western Sichuan plateau in terms of uplift rate and down-shear rate, and combined with the active structure of the Longmenshan to strike slip, the marginal mountains in the eastern margin of the Qinghai-Tibet Plateau are dominated by eroded and uplifted structures, Uplift effect. Finally, according to the time required for the maximum cutting depth of the Minjiang River (3.4 8 Ma) and the time of the Dayi conglomerate, the oldest Minjiang alluvial fan in the Chengdu basin (3.6 Ma