Residence Time of Over‐Steepened Rock Masses in an Active Mountain Range
Residence Time of Over‐Steepened Rock Masses in an Active Mountain Range
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DOI：
10.1029/2021gl097319
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发表时间：
2022-04
影响因子：
5.2
通讯作者：
Gen K. Li;S. Moon;Justin T. Higa
中科院分区：
文献类型：
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作者：
Gen K. Li;S. Moon;Justin T. Higa
在隆起的山脉中，山坡会朝着由基底材料强度设定的阈值角度变陡。超过阈值角度的山坡（称为过度地形）在机械上不稳定。岩体在过量地形中的停留时间尺度（Tex）对于理解陡峭山区地表过程和景观演化的时间尺度至关重要。然而，Tex 对于不同的坡度和岩性仍然存在松散的约束。在这里，我们通过量化跨岩性的过度地形、地震活动和气候引起的长期滑坡侵蚀率以及折返率来计算青藏高原东部山区的 Tex。 Tex 随着局部坡角的增加而增加，并且在不同岩性中具有相同的数量级，但对于变质岩来说稍长一些。范围尺度 Tex 估计为~61-157 kyr，是阈值地形起伏恢复时间跨度的~3-9%。无论岩性和方法如何，类似的 Tex 都表明该造山带在数千至数百万年的时间尺度内存在稳态构造和多余地形的侵蚀。
In uplifting mountains, hillslopes steepen toward a threshold angle set by substrate material strength. Hillslopes beyond the threshold angle, referred to as excess topography, are mechanically unstable. The residence time scale of rock masses in excess topography (Tex) is critical for understanding time scales of surface processes and landscape evolution in steep mountains. However, Tex remains loosely constrained for varying slopes and lithologies. Here, we calculate Tex in the eastern Tibetan mountains by quantifying excess topography across lithologies, long‐term landslide erosion rates caused by seismicity and climate, and exhumation rates. Tex increases with local slope angles and is of the same order of magnitude across different lithologies but slightly longer for metamorphic rocks. Range‐scale Tex is estimated as ∼61–157 kyr, ∼3–9% of the relief‐rejuvenation timespan of threshold topography. Similar Tex regardless of lithologies and methods suggest steady‐state construction and erosion of excess topography over thousand to million years time scales in this orogen.