The 87Sr/86Sr Record of Himalayan Paleorivers During the Neogene: Patterns and Causes

小行星9725607 喜马拉雅山是关于造山运动如何改变气候的争论的中心。 喜马拉雅山隆升的全球影响的最清晰的代理之一是海洋87 Sr/86 Sr记录。 然而，过去和现在的喜马拉雅河流对海洋87 Sr/86 Sr记录的具体贡献，以及这种贡献如何定量转化为硅酸盐风化率，从而消耗大气CO2尚不清楚。 我们最近的研究表明，喜马拉雅古河流的87 Sr/86 Sr比值可以从保存在喜马拉雅褶皱冲断带前缘的西瓦利克群前陆盆地沉积中的碳酸盐中重建。 这些数据表明，87 Sr/86 Sr比值在晚第三纪明显增加，可能是响应于小喜马拉雅和前喜马拉雅推覆体的高87 Sr/86 Sr（0.720-0.729）大理石和白云岩的去顶。 我们建议（1）将喜马拉雅河的87 Sr/86 Sr记录扩展到尼泊尔最东部，并回到中新世开始，从而完成古恒河水系的同位素历史，（2）量化现代尼泊尔河流中碳酸盐与硅酸盐风化的贡献，（3）联合收割机同位素数据与沉积学，构造，和物源数据的前陆盆地沉积物，以记录整个记录的尼泊尔喜马拉雅山脉的侵蚀去顶开始的中新世。 这项研究的结果将对我们理解碰撞造山作用、气候和海水化学之间的关系产生重大影响。

9725607 Quade The Himalayas stand at the center of the debate on how mountain building can alter climate. One of the clearest proxies of the global effects of Himalayan uplift is the marine 87Sr/86Sr record. Yet the specific contribution that past and present Himalayan rivers make to the marine 87Sr/86Sr record, and how this contribution translates quantitatively into silicate weathering rates and therefore consumption of atmospheric CO2 is unclear. Our recent research demonstrates that the 87Sr/86Sr ratios of Himalayan paleorivers can be reconstructed from carbonates preserved in the Siwalik Group foreland basin deposits in the frontal part of the Himalayan fold-thrust belt. These data show 87Sr/86Sr ratios have increased markedly in the late Neogene, probably in response to unroofing of high 87Sr/86Sr (0.720-0.729) marble and dolostone in the Lesser Himalayan and frontal Himalayan nappes. We propose to (1) expand our Himalayan river 87Sr/86Sr record into easternmost Nepal, and back to the beginning of the Miocene, thereby completing the isotopic history for the paleo-Ganges river system, (2) quantify the contribution of carbonate versus silicate weathering in a modern Nepali river, and (3) combine the isotopic data with sedimentological, structural, and provenance data from the foreland basin deposits in order to document the entire record of erosional unroofing of the Nepal Himalayas since the beginning of the Miocene. The results of the proposed research will have major implications for our understanding of the relationships between collisional orogenesis, climate, and ocean water chemistry.