Two Stages of Accelerated Exhumation in the Middle Reach of the Yarlung River, Southern Tibet Since the Mid-Miocene
Two Stages of Accelerated Exhumation in the Middle Reach of the Yarlung River, Southern Tibet Since the Mid-Miocene
复制标题
中新世中期以来藏南雅砻江中游的两期加速剥露
DOI：
10.1029/2020tc006618
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发表时间：
2021
期刊：
影响因子：
4.2
通讯作者：
Wang Cheng-Shan
中科院分区：
文献类型：
--
作者：
Dai Jin-Gen;Fox Matthew;Han Xu;Tremblay Marissa M.;Xu Shi-Ying;Shuster David L.;Liu Bo-Rong;Zhang Jiawei;Wang Cheng-Shan
气候变化和构造活动通过侵蚀控制地球的地形，其中大部分是由河流切割形成的。雅砻河横切了印度-亚洲碰撞带，是地球上最大的河流之一。然而，其侵蚀率历史及其与区域构造的相互作用仍然不明确。在这里，我们对雅砻河基岩样品应用低温测时法和热运动学模型。我们的分析表明，雅砻江中游不同地区出现了两个相对较快的折返阶段，随后是明显较慢的折返速度。首先，雅砻江大部分地区，包括山谷及其支流的大部分地区，发生了中新世中期（15-9 Ma）的快速折返。这一快速折返时期与亚洲边缘盆地记录的高降水率阶段和东西向伸展断裂的时间相吻合。与伸展断层相结合，亚洲季风爆发导致的降水增加将增加河流流量，从而加速中新世中期的折返速率。其次，上新世-更新世（5-2Ma）时期的加速折返仅限于峡谷，这是对南北正断层的响应，这意味着局部构造是一级控制。我们的结果强调了气候和构造过程在塑造河流地形中的作用以及它们如何随时间变化。
Climate change and tectonic activity through erosion control Earth’s topography, much of which is shaped by river incision. The Yarlung River has dissected the Indian‐Asian Collision Zone, and is one of the Earth’s largest rivers. However, its erosion rate history and how it interacts with regional tectonics remain ambiguous. Here, we apply low‐temperature thermochronometry and thermal‐kinematic models for bedrock samples from the Yarlung River. Our analysis reveals two stages of relatively fast exhumation occurred in different parts of the middle reach of the Yarlung River followed by remarkedly slow exhumation rate. First, a mid‐Miocene period (15–9 Ma) of rapid exhumation occurred along much of the Yarlung River, including within wide portions of the valley and its tributaries. This period of rapid exhumation coincides with the stage of high precipitation rates recorded in the Asian marginal basins and the timing of the east‐west extensional faults. In combination with extensional faults, the enhanced precipitation due to the onset of Asian monsoon would increase river discharge and thus accelerate mid‐Miocene exhumation rates. Second, a Pliocene‐Pleistocene (5–2 Ma) period of accelerated exhumation limited to gorges occurred in response to north‐south normal faulting, implying local tectonics as a first‐order control. Our results highlight roles of climatic and tectonic processes in shaping fluvial topography and how these change with time.