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.
