The Himalaya orogen evolved since the Eocene as the Tethyan-, Greater-, Lesser- and Sub-Himalaya thrust sheets were uplifted and exhumed in sequence. Reconstructing the provenance of sediment in Himalayan River systems can inform on stages in the tectonic history of the orogen. Here, we analyze the oxygen, carbon and “clumped” isotope compositions of carbonate minerals from Himalayan bedrock, Ganga River sediments and Bengal Fan turbidite deposits. We demonstrate that river sediments consist of a mixture of Himalayan-derived and authigenic calcite precipitated in the river system. The relative abundance and clumped isotope apparent temperatures of detrital calcite in turbidite deposits decreased between the Late Miocene and Pliocene, while chemical weathering intensity did not increase during this interval. Considered together, these results reflect the establishment of the Lesser Himalaya as an important carbonate sediment source for Himalayan rivers, driven by the uplift and exhumation of this thrust sheet.

中文翻译：

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晚中新世由碎屑碳酸盐的聚集同位素组合物记录的小喜马拉雅山的隆起和挖掘


喜马拉雅造山带自始新世以来随着 Tethyan-、Greater-、Lesser- 和 Sub-Himalaya 逆冲片相继被抬升和挖掘而进化。重建喜马拉雅河系统中沉积物的来源可以了解造山带构造历史的各个阶段。在这里，我们分析了来自喜马拉雅基岩、恒河沉积物和孟加拉扇浊积岩矿床的碳酸盐矿物的氧、碳和“团块”同位素组成。我们证明河流沉积物由河流系统中沉淀的喜马拉雅衍生和自生方解石的混合物组成。晚中新世和上新世之间，浑浊矿床中碎屑方解石的相对丰度和团块同位素表观温度降低，而化学风化强度在此期间没有增加。综合考虑，这些结果反映了小喜马拉雅山成为喜马拉雅河流重要的碳酸盐沉积物来源，这是由该逆冲板的抬升和挖掘驱动的。