The Himalayan syntaxes, characterized by extreme rates of rock exhumation co-located with major trans-orogenic rivers, figure prominently in the debate on tectonic versus erosional forcing of exhumation. Both the mechanism and timing of rapid exhumation of the Namche Barwa massif in the eastern syntaxis remain controversial. It has been argued that coupling between crustal rock advection and surface erosion initiated in the late Miocene (8-10 Ma). Recent studies, in contrast, suggest a Quaternary onset of rapid exhumation linked to a purely tectonic mechanism. We report new multisystem detrital thermochronology data from the most proximal Neogene clastic sediments downstream of Namche Barwa and use a thermo-kinematic model constrained by new and published data to explore its exhumation history. Modeling results show that exhumation accelerated to ~4 km/m.y. at ~8 Ma and to ~9 km/m.y. after ~2 Ma. This three-stage history reconciles apparently contradictory evidence for early and late onset of rapid exhumation, and suggests efficient coupling between tectonics and erosion since the late Miocene. Quaternary acceleration of exhumation is consistent with river-profile evolution, and may be linked to a Quaternary river-capture event.

中文翻译：

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喜马拉雅东部 Namche Barwa 构造结快速折返的早发和晚加速

喜马拉雅构造以与主要跨造山河流共同定位的极端岩石剥脱速率为特征，在关于构造与侵蚀强迫剥脱的辩论中占有突出地位。东部构造构造区 Namche Barwa 地块快速挖掘的机制和时间仍然存在争议。有人认为地壳岩石平流和地表侵蚀之间的耦合始于中新世晚期（8-10 Ma）。相比之下，最近的研究表明，第四纪开始的快速挖掘与纯粹的构造机制有关。我们报告了来自 Namche Barwa 下游最近的新近纪碎屑沉积物的新多系统碎屑热年代学数据，并使用受新数据和已发表数据约束的热运动学模型来探索其挖掘历史。建模结果表明，在~8 Ma 时剥落加速到~4 km/my，在~2 Ma 后加速到~9 km/my。这三个阶段的历史协调了早期和晚期快速挖掘的明显矛盾的证据，并表明自晚中新世以来构造和侵蚀之间存在有效耦合。第四纪剥落加速与河流剖面演化一致，可能与第四纪河流捕获事件有关。