Erosional control on the dynamics of low-convergence rate continental plateau margins
Erosional control on the dynamics of low-convergence rate continental plateau margins
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DOI：
10.1111/j.1365-246x.2009.04324.x
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发表时间：
2009-11
影响因子：
2.8
通讯作者：
V. Godard;R. Cattin;J. Lavé
中科院分区：
文献类型：
--
作者：
V. Godard;R. Cattin;J. Lavé
总结 在过去的十年中，热机械模型揭示了构造和侵蚀对大陆高原边缘形态的控制。然而，在实践中阐明这两个耦合过程的具体影响一直很困难。在这里，为了评估侵蚀的控制，我们研究了青藏高原东部和北部边界的动态，这些边界的特点分别是与四川盆地和塔里木盆地相邻的低收敛速度和陡峭的地形悬崖。大陆岩石圈与河流剥蚀相结合的热机械模型表明，作为对重力塌陷和侵蚀卸载引起的质量传递的响应，可能会发生具有大规模水平位移的重要地壳变形，而不会发生任何收敛。这些过程对地壳结构、地温梯度以及地表侵蚀很敏感。在几百万年的时间尺度上，我们的结果表明，这种剥蚀引发的变形通过平衡侵蚀引起的质量去除和稳定地形悬崖，对这些高原边缘的演化发挥了主要控制作用。这一发现支持了对西藏东部龙门山形态的可能解释，其中靠近前陆的持续高地形梯度和低收敛率的矛盾组合可能与侵蚀对变形模式的影响有关。
S U M M A R Y Over the last decade, thermomechanical models have revealed the control of both tectonics and erosion on the morphology of continental plateaus margins. However, unravelling the specific effects of these two coupled processes has been difficult in practice. Here, to assess the control of erosion, we investigate the dynamics of the eastern and the northern borders of the Tibetan Plateau, which are characterized by a low convergence rate and a steep topographic escarpment adjacent to the Sichuan and Tarim basins, respectively. Thermomechanical modelling of continental lithosphere coupled with fluvial denudation reveals that important crustal deformation with large-scale horizontal displacements can occur, without any convergence, as a response to mass transfer due to gravitational collapse and to erosional unloading. These processes are sensitive to crustal structure, geothermal gradient as well as surface erosion. At a timescale of several million years, our results suggest that this denudation-triggered deformation exerts a primary control on the evolution of those plateau margins by counterbalancing the mass removal due to erosion and stabilizing the topographic escarpment. This finding supports a possible explanation for the morphology of the Longmen Shan, eastern Tibet, in which the paradoxical combination of persistent high-topographic gradients close to the foreland and low convergence rates can be related to the influence of erosion on deformation patterns.