Sr-Nd-Os evidence for a stable erosion regime in the Himalaya during the past 12 Myr
Sr-Nd-Os evidence for a stable erosion regime in the Himalaya during the past 12 Myr
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DOI：
10.1016/j.epsl.2010.01.004
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发表时间：
2010-02-20
影响因子：
5.3
通讯作者：
Huyghe, Pascale
中科院分区：
文献类型：
--
作者：
Galy, Valier;France-Lanord, Christian;Huyghe, Pascale
喜马拉雅山脉是世界上最大的山脉，现代的侵蚀将巨大的溶解物和颗粒物转移到海洋中。它在长期的全球碳循环中起着重要作用，主要是通过加强孟加拉扇的有机碳埋藏。为了了解过去喜马拉雅山侵蚀的作用，必须确定气候变化和构造对侵蚀的影响。在这里，我们使用12万年的沉积记录从远孟加拉扇（深海钻探项目网站218）重建喜马拉雅侵蚀的中-上新世的历史。我们使用有机质的碳稳定同位素（δ C-13）作为古环境指标和地层工具。利用Sr、Nd和Os等多种同位素数据，对孟加拉扇沉积物的来源进行了研究。大量有机质的δ C-13值急剧地向较少贫化的值移动，揭示了广泛的晚中新世（约1000年）。7.4 Ma）盆地C4植物的扩张。Sr，Nd和Os同位素组成表明，在喜马拉雅山脉在过去的12万年相当稳定的侵蚀模式。这支持了藏南高原与孟加拉扇之间存在强烈联系。喜马拉雅山脉和西藏南部的构造演化似乎无法产生大规模的水系重组。此外，我们的数据并没有表明在过去的1200万年藏南高原的海拔高度的快速变化。Sr和Nd同位素组成的变化在中新世晚期C4植物的扩张周围的高喜马拉雅结晶岩的侵蚀的相对增加（即同时减少transshimalayan岩基和小喜马拉雅相对贡献）。这可能与当时生态和沉积学变化所暗示的干旱增加有关。在上新世-更新世过渡期，Sr和Nd同位素组成呈相反的趋势，这可能与喜马拉雅山的降水量增加和冰川发育有关。在晚中新世和上新世-更新世过渡期，这些几乎同步的侵蚀模式和气候变化的温和变化支持了这一时期气候对喜马拉雅侵蚀的主导控制的概念。然而，在更新世稳定的侵蚀制度是暗示了喜马拉雅侵蚀的冰川发展的影响有限。(C)2010爱思唯尔有限公司版权所有。
Modern erosion of the Himalaya, the world's largest mountain range, transfers huge dissolved and particulate loads to the ocean. It plays an important role in the long-term global carbon cycle, mostly through enhanced organic carbon burial in the Bengal Fan. To understand the role of past Himalayan erosion, the influence of changing climate and tectonic on erosion must be determined. Here we use a 12 Myr sedimentary record from the distal Bengal Fan (Deep Sea Drilling Project Site 218) to reconstruct the Mio-Pliocene history of Himalayan erosion. We use carbon stable isotopes (delta C-13) of bulk organic matter as paleo-environmental proxy and stratigraphic tool. Multi-isotopic - Sr, Nd and Os - data are used as proxies for the source of the sediments deposited in the Bengal Fan over time. delta C-13 values of bulk organic matter shift dramatically towards less depleted values, revealing the widespread Late Miocene (ca. 7.4 Ma) expansion of C4 plants in the basin. Sr, Nd and Os isotopic compositions indicate a rather stable erosion pattern in the Himalaya range during the past 12 Myr. This supports the existence of a strong connection between the southern Tibetan plateau and the Bengal Fan. The tectonic evolution of the Himalaya range and Southern Tibet seems to have been unable to produce large re-organisation of the drainage system. Moreover, our data do not suggest a rapid change of the altitude of the southern Tibetan plateau during the past 12 Myr. Variations in Sr and Nd isotopic compositions around the late Miocene expansion of C4 plants are suggestive of a relative increase in the erosion of High Himalaya Crystalline rock (i.e. a simultaneous reduction of both Transhimalayan batholiths and Lesser Himalaya relative contributions). This could be related to an increase in aridity as Suggested by the ecological and sedimentological changes at that time. A reversed trend in Sr and Nd isotopic compositions is observed at the Plio-Pleistocene transition that is likely related to higher precipitation and the development of glaciers in the Himalaya. These almost synchronous moderate changes in erosion pattern and climate changes during the late Miocene and at the Plio-Pleistocene transition support the notion of a dominant control of climate on Himalayan erosion during this time period. However, stable erosion regime during the Pleistocene is suggestive of a limited influence of the glacier development on Himalayan erosion. (C) 2010 Elsevier B.V. All rights reserved.