Erosional Unroofing of the Nepal Himalayas Over the Past 12Ma: 87Sr/86Sr and Sedimentary Petrological Indicators from Siwalik Foreland Deposits

9418207 Quade 喜马拉雅山隆起沉积物的风化对海洋化学、区域（现在季风）气候以及可能对大气 pCO2 产生了重大影响。 喜马拉雅隆升影响最清晰的代表之一是海洋 87Sr/86Sr 记录。 然而，海洋 Sr 记录与喜马拉雅腹地的构造运动和风化速率之间的具体联系实际上没有记录。 喜马拉雅山侵蚀的中新世-更新世碎屑记录包含在暴露于喜马拉雅山锋岭和孟加拉海底扇的西瓦利克群前陆盆地沉积物中。 这项研究将研究过去 12 Ma 期间尼泊尔中西部沉积物 Siwalik 沉积物中沉积物、风化产物和水生（河流）贝壳的 87Sr/86Sr 比率的变化。 这些同位素组成将与喜马拉雅山的特定构造和侵蚀事件相关，从而提供造山带物理过程（例如单个逆冲位移事件）与沉积物和水成分变化之间的直接联系。 反过来，这些研究将允许将 Siwalik 沉积物的 87Sr/86Sr 比率和其他方面的变化与海洋和孟加拉海底扇沉积物的同位素演化进行比较。

9418207 Quade Weathering of sediments derived from uplift of the Himalayas has had a major impact on the chemistry of the oceans, on regional (now monsoonal) climate, and probably on atmospheric pCO2. One of the clearest proxies of the effects of Himalayan uplift is the marine 87Sr/86Sr record. However, the specific links between the marine Sr record and tectonism and weathering rates in the Himalayan hinterland are virtually undocumented. The Miocene-Pleistocene detrital record of erosion of the Himalayas is contained in the Siwalik Group foreland-basin sediments exposed in the Himalayan frontal ranges, and in the Bengal submarine fan. This research will examine changes in the 87Sr/86Sr ratio of sediment, weathering products, and aquatic (riverine) shells in Siwalik sediments deposited in central and western Nepal over the past 12 Ma. These isotopic compositions will be correlated with specific tectonic and erosional events in the Himalayas, providing a direct link between physical processes in the orogenic belt (e.g., individual thrust-displacement events) and changes in sediment and water composition. In turn, these studies will permit comparison of changes in 87Sr/86Sr ratios and other aspects of Siwalik sediments to the isotopic evolution of the ocean and Bengal submarine fan sediments.