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Formation of amphitheater-headed canyons.

机译：圆形剧场为首的峡谷的形成。

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摘要

The amphitheater headwalls of some bedrock canyons have been used to infer the environmental conditions and erosion processes responsible for shaping the surfaces of Earth and Mars. Morphologic identification of process is hampered, however, because we lack basic field observations and quantitative models of erosion and sediment-transport in bedrock canyons. Herein I describe five related efforts to identify erosion and transport processes through field observations and measurements of canyons on Earth, and to develop quantitative models for some of these processes. First, I present a compilation of new observations and those of others, and conclude that, despite assertions that amphitheater form is due to groundwater-seepage erosion, the evidence to support this hypothesis is ambiguous or nonexistent for most bedrock canyons. A detailed examination of two prominent examples, the Kohala valleys in Hawai'i and Box Canyon in Idaho, has revealed no evidence for seepage erosion. Instead, field observations and topographic analyses of the Kohala valleys suggest that they likely formed by waterfall plunge-pool erosion following large-scale slumping of Kohala Volcano. In addition, sediment transport measurements and dating indicate that Box Canyon owes its origin to large-scale flooding that occurred about 45 thousand years ago. To better quantify erosion and transport processes, a mechanistic model is presented to predict the conditions under which coarse sediment is mobilized in rivers and streams over a wide range of channel-bed slopes. Lastly, I present a model for abrasion of bedrock riverbeds by impacting particles carried in bedload and suspended load.
机译：一些基岩峡谷的圆形剧场顶壁已被用于推断环境条件和侵蚀过程，这些过程和侵蚀过程负责塑造地球和火星的表面。但是，由于缺乏基本的野外观察以及基岩峡谷中侵蚀和泥沙输送的定量模型，因此无法对过程进行形态学识别。在这里，我描述了五项相关的工作，这些工作通过实地观察和对地球上峡谷的测量来识别侵蚀和运输过程，并为其中一些过程开发定量模型。首先，我提出了一些新观测值和其他观测值的汇总，并得出结论，尽管断言圆形剧场的形成是由于地下水渗流侵蚀所致，但对于大多数基岩峡谷来说，支持这一假说的证据是模棱两可的或不存在的。对两个著名的例子，夏威夷的科瓦拉山谷和爱达荷州的博克斯峡谷的详细检查没有发现渗流侵蚀的证据。相反，对科哈拉山谷的野外观测和地形分析表明，它们很可能是由科哈拉火山大规模塌陷后瀑布下的瀑布潭侵蚀形成的。此外，沉积物的运输测量和年代测定表明，Box Canyon的起源是大约45,000年前发生的大规模洪水。为了更好地量化侵蚀和运输过程，提出了一种机械模型来预测在大范围河床河床斜坡上河流和溪流中动员粗沙的条件。最后，我提出了一种通过影响床荷和悬浮荷重中的颗粒来磨损基岩河床的模型。

著录项

  • 作者

    Lamb, Michael Patrick.;

  • 作者单位

    University of California, Berkeley.;

  • 授予单位 University of California, Berkeley.;
  • 学科 Physical Geography.;Geology.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 312 p.
  • 总页数 312
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 自然地理学;地质学;
  • 关键词

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