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

9418207喜马拉雅山脉抬升产生的沉积物的快速风化对海洋的化学成分、区域(现在的季风气候)以及可能对大气二氧化碳产生了重大影响。最清晰的喜马拉雅隆升效应的代表之一是海相87Sr/86Sr记录。然而，海洋锶记录与喜马拉雅腹地的构造作用和风化速率之间的具体联系几乎没有文献记载。喜马拉雅前缘山脉出露的Siwalik群前陆盆地沉积和孟加拉海底扇中含有中新世-更新世喜马拉雅山脉侵蚀的碎屑记录。这项研究将研究尼泊尔中西部Siwalik沉积物中沉积物、风化产物和水生(河流)贝壳在过去12 Ma期间的87Sr/86Sr比值的变化。这些同位素组成将与喜马拉雅地区的特定构造和侵蚀事件相关联，在造山带的物理过程(例如，个别的逆冲-置换事件)与沉积物和水成分的变化之间提供直接联系。反过来，这些研究将允许将Siwalik沉积物的87Sr/86Sr比值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.