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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Erosion and exhumation in the Himalaya from cosmogenic isotope inventories of river sediments
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Erosion and exhumation in the Himalaya from cosmogenic isotope inventories of river sediments

机译：河流沉积物的宇宙成因同位素清单对喜马拉雅山的侵蚀和挖掘

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The outward erosional flux is a key factor in the tectonic evolution of mountain belts and there is much debate about the feedbacks between tectonics, erosion and climate. Here we use cosmogenic nuclides (~(10)Be and ~(26)Al) analysed in quartz from river sediments from the Upper Ganges catchment to make the first direct measurements of large-scale erosion rates in a rapidly uplifting mountain belt. The erosion rates are highest in the High Himalaya at 2.7 ± 0.3 mm/yr (1σ errors), fall to 1.2 ± 0.1 mm/yr on the southern edge of the Tibetan Plateau and are 0.8 ± 0.3 to <0.6 mm/yr in the foothills to the south of the high mountains. These relative estimates are corroborated by the Nd isotopic mass balance of the river sediment. Analysis of sediment from an abandoned terrace suggests that similar erosion rates have been maintained for at least the last few thousand years. The data presented here, along with data recently published for European river catchments, demonstrate that a log-linear relationship between relief and erosion rate holds over three orders of magnitude variation in erosion rate and between very different climatic and tectonic regimes. The erosion rate estimates from cosmogenic nuclides correlate well with exhumation rates calculated from previously published apatite fission track ages in the Indian Himalaya. This confirms that much of the exhumation in the Himalayan mountain chain is now balanced by erosion. However, exhumation rates calculated from high blocking temperature systems, such as ~(40)Ar/~(39)Ar in muscovite, imply lower exhumation rates. Rocks presently at the surface must have undergone a three-to six-fold increase in exhumation rate within the last few million years. We show how this could be explained either by climatic forcing of erosion rate changes or by tectonics. Published evidence for equally rapid changes of exhumation rate in the past and the probable diachroneity in the time at which the present exhumation rates accelerated imply that tectonics has moderated at least some of the change in exhumation rates.
机译：向外的侵蚀通量是山区构造演化的关键因素，关于构造，侵蚀和气候之间的反馈存在很多争议。在这里，我们使用恒河上游流域河流沉积物中石英中的宇宙成因核素（〜（10）Be和〜（26）Al）进行分析，以首次直接测量快速抬升的山区大尺度侵蚀速率。高喜马拉雅山的侵蚀速率最高，为2.7±0.3 mm / yr（1σ误差），在青藏高原南缘下降至1.2±0.1 mm / yr，在青藏高原的侵蚀速率为0.8±0.3至<0.6 mm / yr。高山南部的山麓小丘。这些相对估计值由河流沉积物中的Nd同位素质量平衡所证实。对一个废弃的梯田的沉积物的分析表明，至少最近几千年来一直保持着相似的侵蚀速率。此处提供的数据以及最近发布的有关欧洲河流集水区的数据表明，救济与侵蚀速率之间的对数线性关系在侵蚀速率上以及在非常不同的气候和构造类型之间保持三个数量级以上的变化。来自宇宙成因核素的侵蚀速率估计值与根据印度喜马拉雅山先前公布的磷灰石裂变径迹年龄计算出的发掘速率有很好的相关性。这证实了喜马拉雅山脉的许多发掘工作已被侵蚀所平衡。然而，从高阻断温度系统计算出的发掘率，例如白云母中的〜（40）Ar /〜（39）Ar，意味着更低的发掘率。在过去的几百万年中，目前地表的岩石的发掘率必须提高三到六倍。我们展示了如何通过侵蚀速率变化的气候强迫或构造来解释这一点。已发表的证据表明，过去的尸体发掘率变化同样迅速，而目前的尸体发掘速度加快时可能出现双眼错误，这表明构造学至少缓和了某些尸体发掘率的变化。

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