青藏高原中部河流切口的地形起伏响应：来自宇宙成因10Be的证据,Journal of Geophysical Research: Earth Surface

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青藏高原中部河流切口的地形起伏响应：来自宇宙成因10Be的证据
Journal of Geophysical Research: Earth Surface ( IF 3.5 ) Pub Date : 2021-10-14 , DOI: 10.1029/2021jf006111
Ye Yang ₁ , Li‐Feng Cui ₁ , Sheng Xu ₁ , Cong‐Qiang Liu ₁ , Derek Fabel ₂

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河流切割被认为是基本的地貌过程之一，推动了山地景观的演变。受河流动态、气候变化和构造抬升的影响，青藏高原中部由低地势到高地势的过渡景观正在迅速演变。本研究结合宇宙成因¹⁰ Be 深度剖面定年和地形分析，为青藏高原中部低地势面的形成和破坏提供了新的约束条件。我们发现索曲地区（怒江上游的主要支流）的高地貌景观显示出710±70 mm kyr ^-1的快速河流切割率晚更新世以来，而邻近下丘曲地区的低地势地形呈现出70±10 mm kyr ^-1较低的切割率一个数量级. 这些结果与来自低温热年代学的长期（数百万年）挖掘率一致，表明该地区经历了不断发展的切口历史。我们认为较高的地势是由增强的河流切口引起的，较低的地势是由沉积和相对稳定的低折返率缓慢形成的。knickzone 的存在似乎标志着这些差异切割景观之间的边界，这可能是由于索曲河的快速前退和更高的河流流量造成的。除了古侵蚀率外，河流阶地年龄与气候驱动事件的巧合，

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Topographic Relief Response to Fluvial Incision in the Central Tibetan Plateau: Evidence From Cosmogenic 10Be

Fluvial incision, regarded as one of the fundamental geomorphic processes, drives the evolution of mountainous landscapes. The transitional landscape from low-relief to high-relief in the central Tibetan Plateau is rapidly evolving as it is influenced by river dynamics, climate change and tectonic uplift. Combining cosmogenic ¹⁰Be depth profile dating and topographic analysis, this study provides new constraints on the formation and destruction of low-relief surfaces in the central Tibetan Plateau. We find that the high-relief landscape in the Suoqu area (a major tributary of the upper Nu River) shows a rapid fluvial incision rate of 710 ± 70 mm kyr⁻¹ since the late Pleistocene, while the low-relief topography in the adjacent Xiaqiuqu area presents an order of magnitude lower incision rate of 70 ± 10 mm kyr⁻¹. These results are consistent with the long-term (multi-million-year) exhumation rates derived from low-temperature thermochronology, suggesting that this region has experienced an evolving incision history. We interpret that the higher relief was caused by enhanced fluvial incision, and the lower relief was slowly developed by sedimentation and relatively steady low exhumation rate. The presence of a knickzone appears to mark the boundary between these differentially incising landscapes, which may be caused by rapid headward retreat and higher river discharge in the Suoqu River. The coincidence of fluvial terraces ages with climate-driven events, in addition to paleodenudation rates, indicates that the formation of fluvial terraces in the Xiaqiuqu and Suoqu areas might be associated with the quick sedimentation of weathered materials in early warming periods.

更新日期：2021-10-25

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