Geomorphic and geochronologic study in and near Grand Canyon: Testing landscape responses to climate change and exploring the paleo-longitudinal profile of the Colorado River

景观对气候变化的响应和高架地形的切割是地貌学中基本但尚未完全理解的问题。 大峡谷景观包含了这两个更大的过程的一个异常保存完好和暴露的记录。 我们更大的研究小组正在进行的工作表明，米兰科维奇规模的气候变化的强烈景观响应已被叠加在长期的切口率约150米/我在大峡谷东部，和可变的切口率沿着大峡谷的长度可能与第四纪断层。 我们的详细测绘和初步定年的第四纪地层在东部大峡谷导致了一个新的概念模型旱地气候的反应，包括复杂的联系和之间的相位关系的山坡，支流，和主干科罗拉多河在中晚更新世气候变化。 一幅相对活跃和空间可变的区域切割的画面正在出现，它暴露了景观对气候变化反应的丰富记录。 我们提出的研究，结合光激发光，在现场宇宙成因核素，和U-系列测年与详细的现场地貌研究的壮观的山坡和冲积地层在头部，内部，并在大峡谷的终端的三个关键位置。 我们在大峡谷东部的实地考察和地质年代学研究，导致了两个研究重点和相关的假设，我们提出解决。 首先是当地流域对气候的反应。我们的工作概念模型的景观对气候的响应在大峡谷东部（包括在最近提交给GSA公报的手稿）比以前的模型更具体和详细。 它强调了旱地的独特反应，并与全球变暖预测的变化相关。 我们建议通过调查预测的时间海侵加积和切口向下和向上移动的支流，我们假设这是负责支流和主干科罗拉多河加积和切口的意外反相，来测试和完善这个模型。我们的工作假设是，这种反相位一方面是由与当地沉积物供应的产生和沉积信号向下传递到集水区有关的滞后时间引起的，另一方面是由基准面下降信号向上传播的延迟引起的，这是由于当地大量的沉积supply.is通过详细的沉积学、地层学，特别是地质年代学研究来检验。第二个研究重点是科罗拉多河沿着其区域剖面的基岩下切。 我们建议在两个新的研究地点，沿科罗拉多河的长度沿着的关键点，以补充我们现有的数据在东部和西部的大峡谷的长期切口率测定。 沿科罗拉多450 km横断面的冲积层、存款成分和下切率沿着的比较是记录河流的长剖面演变和测试假设的knickzones或通过河流系统的下切波的基本条件，以响应活动的飓风-托罗韦普断层带或更古老的排水捕获区的新构造作用力。 壮观的保存和曝光的完整的山坡支流mainstem第四纪地层在三个研究地点，结合使用三个互补的地质年代学方法，将阐明当地景观和大陆规模的河流之间的复杂联系，以及它们对气候和构造扰动的反应。 此外，这项研究将提供一个启发性的比较三种断代方法，并将有助于完成这个著名地区的景观演变的新兴理解。 我们的研究人员和来自不同机构的学生的参与，开始科学家的培训，以及通过国家公园服务向公众传达结果的框架，确保拟议的研究将产生广泛的影响。

The response of landscapes to climate change and the incision of elevated terrain are fundamental yet incompletely understood issues in geomorphology. The Grand Canyon landscape contains an unusually well-preserved and exposed record of both of these greater processes. Ongoing work by our larger research group indicates that strong landscape responses to Milankovich-scale climate changes have been superimposed on longer-term incision rates of ~150 m/my in eastern Grand Canyon, and that variable incision rates along the length of Grand Canyon can be related to Quaternary faulting. Our detailed mapping and initial dating of the Quaternary stratigraphy in eastern Grand Canyon has resulted in a new conceptual model for dryland responses to climate that includes complex linkages and out-of-phase relations between hillslopes, tributary streams, and the mainstem Colorado River during middle-late Pleistocene climate changes. A picture is emerging of regional incision that is relatively active and spatially variable, and that exposes a rich record of landscape responses to climate change. We propose research that combines optically-stimulated luminescence, in situ cosmogenic nuclide, and U-series dating with detailed field-geomorphic research on the spectacular hillslope and alluvial stratigraphy at three key locations at the head, within, and at the terminous of Grand Canyon. Our fieldwork and geochronology in eastern Grand Canyon has led to two research emphases and related hypotheses we propose to address. First is local catchment responses to climate. Our working conceptual model of landscape responses to climate in eastern Grand Canyon (included in a manuscript recently submitted to GSA Bulletin) is more specific and detailed than previous models. It highlights the unique responses of drylands and is pertinent to the changes predicted with global warming. We propose to test and refine this model by investigating the predicted time-transgressive aggradation and incision moving down and up tributary streams, which we hypothesize is responsible for the unexpected antiphasing of tributary and mainstem Colorado River aggradation and incision. Our working hypothesis.that such antiphasing is caused on one hand by a lag time associated with the production of local sediment supply and the passing of that sedimentary signal down the catchment, and on the other hand by a delay in the progression of the signal of base-level fall up the catchment due to locally great sediment supply.is testable via detailed sedimentologic, stratigraphic, and especially geochronologic study. The second research emphasis is the bedrock incision of the Colorado River along its regional profile. We propose to add long-term incision rate determinations at two new study sites at key points along the length of the Colorado River to complement our existing data in eastern and western Grand Canyon. Comparison of the alluvial stratigraphy, deposit composition, and incision rates along this 450-km transect of the Colorado are basic to recording the river.s long-profile evolution and testing for hypothesized knickzones or waves of incision passing through the fluvial system in response to neotectonic forcing at the active Hurricane-Toroweap fault zone or much older drainage capture. The spectacular preservation and exposure of the complete hillslope-tributary-mainstem Quaternary stratigraphy at the three study sites, in combination with the use of three complimentary geochronologic methods, will elucidate the complex linkages between the local landscape and a continental-scale river and their responses to climatic and tectonic perturbations. In addition, this research will provide an enlightening comparison of the three dating methods, and will help complete the emerging understanding of landscape evolution of this famous area. Our involvement of researchers and students from diverse institutions, training of beginning scientists, and framework for communicating results to the public via the National Park Service insure that the proposed research will have broad impact.