Plio-Pleistocene History of River Incision and Catchment Erosion From Cosmogenic 26 AL and 10 BE in Cave Sediments

9706011格兰杰 河流穿过基岩的速率和模式决定了地貌如何根据其构造和气候环境而演变。 了解长期的河流下切过程对于了解地貌演化、构造隆起模式、气候变化的地貌记录以及土地利用和大坝建设的环境影响非常重要。 然而，由于长期河流下切率以前很难测量，河流下切率仍然没有得到很好的约束，河流下切的理论模型在很大程度上仍然未经检验。 最近，宇宙成因核素技术提供了新的工具，估计长期河流切割率和集水侵蚀率。 现在可以推断河流剖面演变相关的时间尺度上的河流下切和集水侵蚀速率的详细历史。 该项目使用保存在肯塔基州绿色河沿岸洞穴中的河流沉积物中的26 Al和10 Be来推断过去500万年来河流切割和集水侵蚀的历史。 由于洞穴提供了一个不受侵蚀的环境，洞穴沉积物可以保持数百万年不受干扰。 绿色河流经众多洞穴，包括猛犸洞穴系统，迄今为止世界上最大的洞穴系统，调查通道超过500公里。 这些洞穴是河流沉积物的巨大储存库，记录了过去500万至1000万年来河流的切割历史。 对猛犸洞穴系统沉积物的密集采样将允许详细重建过去500万年来的河流切割和集水侵蚀，这一时间跨度包括几次重大的气候变化。 沿绿色河的长度沿着进行额外的采样，将允许研究同一时间跨度内河流的纵向剖面演变。 这些数据将提供一个前所未有的范围和详细的河流切割和集水侵蚀的记录。 本研究旨在探讨泥沙供应对河流下切的影响，同时测量流域侵蚀（河流泥沙的来源）和河流下切率。 它还应有助于澄清气候变化对河流下切和景观演变的影响。 这项研究应该提供急需的数据来测试和约束河流通过基岩切割的最基本的假设。

9706011 Granger The rate and pattern of river incision through bedrock determines how landscapes evolve in response to their tectonic and climatic environment. Understanding long-term river incision processes is important for understanding landform evolution, patterns of tectonic uplift, the geomorphic record of climate change, and the environmental impacts of land use and dam construction. However, because long-term river incision rates have previously been very difficult to measure, river downcutting rates remain poorly constrained, and theoretical models of river incision remain largely untested. Recently, cosmogenic nuclide techniques have provided new tools for estimating both long-term river incision rates and catchment erosion rates. It is now possible to infer detailed histories of river incision and catchment erosion rate over timescales relevant to river profile evolution. This project uses comogenic 26Al and 10Be in river sediments preserved in caves alongside the Green River, Kentucky, to infer the history of river incision and catchment erosion over the past 5 million years. Because caves provide an environment protected from erosion, cave sediments may be left undisturbed for millions of years. The Green River flows alongside numerous caves, including the Mammoth Cave system, by far the world's largest cave system with over 500 km of surveyed passage. These caves are a vast repository of river sediment, recording the river's incision history over the past 5-10 million years. Intense sampling of the Mammoth Cave system sediments will allow a detailed reconstruction of river incision and catchment erosion over the past 5 million years, a timespan which includes several major climate changes. Additional sampling along the length of the Green River will allow a study of the river's longitudinal profile evolution over the same timespan. These data will provide a record of river incision and catchment erosion unprecedented in its scope and detail. This research is des igned to explore the influence of sediment supply on river incision, by simultaneously measuring both catchment erosion (the source of river sediment) and river downcutting rates. It should also help clarify the influence of climate change on river downcutting and landscape evolution. This study should provide much-needed data to test and constrain the most fundamental hypotheses of river incision through bedrock.