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

9706011格兰杰河流切割基岩的速度和模式决定了景观如何随着其构造和气候环境的变化而演变。了解长期的河流切割过程对于了解地貌演变、构造抬升模式、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，由于以前很难测量长期的河流切割率，河流切削率仍然没有得到很好的约束，河流切割的理论模型在很大程度上仍然没有得到检验。最近，宇宙核素技术为估计长期河流切割率和流域侵蚀率提供了新的工具。现在可以推断与河流剖面演变相关的时间尺度上河流切割和集水区侵蚀率的详细历史。该项目使用保存在肯塔基州格林河沿岸洞穴中的河流沉积物中的同源26Al和10Be来推断过去500万年来河流切割和集水区侵蚀的历史。由于洞穴提供了免受侵蚀的环境，洞穴沉积物可能会在数百万年内保持不受干扰。绿河流经许多洞穴，包括猛犸象洞穴系统，这是迄今为止世界上最大的洞穴系统，有超过500公里的勘测通道。这些洞穴是河流沉积物的巨大储存库，记录了过去500-1000万年来河流的切割历史。对猛犸象洞穴系统沉积物的密集采样将使人们能够详细重建过去500万年来的河流切割和集水区侵蚀，这一时间跨度包括几个主要的气候变化。沿绿河长度的额外采样将允许在相同的时间跨度内研究河流的纵向剖面演变。这些数据将提供前所未有的河流切割和集水侵蚀的记录，其范围和细节都是前所未有的。本研究旨在通过同时测量流域侵蚀(河流泥沙的来源)和河流下切率，来探讨来沙对河流切割的影响。它还应该有助于澄清气候变化对河流削减和景观演变的影响。这项研究应该提供急需的数据，以检验和约束河流切割穿过基岩的最基本假设。

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.