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Geomorphology of laterally advected fault blocks in convergent orogens.

机译：会聚造山带横向平移断层块的地貌。

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摘要

Although the kinematics of bedrock in tectonically active mountain ranges commonly includes large horizontal components, few studies have addressed what the effect of this motion might be on geomorphology. Using a 2-D landscape evolution model, I investigate the role of lateral bedrock motion in steady-state topography developed on fault-bend folds and on extruding plateau margins. The first study, of fault-bend fold topography, examines the role that lateral bedrock motion has on the longitudinal profile shapes of detachment-limited streams. The primary effect is that streams on the fold that flow in the direction of lateral advection have greater steepness and concavity indices than streams that flow the opposite direction. This results from the fact that steady-state erosion rate is a function of bedrock velocity as well as topographic slope and aspect. Erosion rates are greater on a given surface sloping in the direction of advection than on a similar surface facing the opposite direction. Similarly, steeper slopes facing in the direction of advection must erode at faster rates than gentler slopes. This effect is enhanced at faster bedrock velocities, at intermediate fault dips, for thinner hanging walls, and for lower erosion coefficients. Because stream profiles set the relief structure of most mountain ranges, the cross-sectional asymmetry of their range-scale topography results from this mechanism. Hillslope diffusion does not strongly influence this asymmetry at the common length-scales of mountain range half-widths and for reasonable diffusivities. Model results compare favorably to active fault-bend fold topography in the Siwalik Hills, Nepal. The second study shows how topography, such as transversely oriented valleys and ridges, can be advected across the crest of a fault-bend fold. This advection results in a cross-correlation between elevations on the two sides of the mountain range, promoted by the same conditions listed above. The third study demonstrates how lateral advection of an extruding plateau margin, where bedrock motion is limited to a block bounded by an upper normal fault and a lower thrust fault, creates convexo-concave detachment-limited stream longitudinal profiles that are shown to be consistent with observations of trans-Himalayan streams as they cross the Higher Himalaya.
机译：尽管在构造活跃的山脉中，基岩的运动学通常包括较大的水平分量，但很少有研究探讨这种运动可能对地貌的影响。使用二维景观演化模型，我研究了横向基岩运动在断层弯曲褶皱和挤压高原边缘发育的稳态地形中的作用。断层弯曲褶皱地貌的第一项研究考察了横向基岩运动对有限分离流的纵向剖面形状的影响。主要效果是，沿横向对流方向流动的褶皱上的水流比沿相反方向流动的水流具有更大的陡度和凹度指数。这源于以下事实：稳态侵蚀速率是基岩速度以及地形坡度和坡度的函数。在对流方向上倾斜的给定表面上的腐蚀速率要比在相反方向上的相似表面的腐蚀速率更大。同样，面对平流方向的较陡坡必须比较缓的坡以更快的速度侵蚀。在基岩速度更快，断层中间倾斜，悬壁更薄以及侵蚀系数更低的情况下，这种效果会增强。由于河流剖面确定了大多数山脉的浮雕结构，因此，这种机理导致了其山脉尺度地形的横截面不对称性。在常见的山峰半宽长度尺度上以及合理的扩散率下，山坡扩散不会强烈影响这种不对称性。模型结果与尼泊尔Siwalik Hills的活动断层弯曲褶皱地形相比具有优势。第二项研究表明如何在断层弯曲褶皱的顶峰上平移地形，例如横向的山谷和山脊。该平流导致山脉两侧海拔之间的互相关，这由上面列出的相同条件所促进。第三项研究表明，挤压基岩边缘的横向平流如何将基岩运动限制在一个由上法向断层和下推力断层界定的块体上，从而产生凸凹分离限制的河流纵向剖面，该剖面与喜马拉雅山脉横穿喜马拉雅山高流时的观测。

著录项

  • 作者

    Miller, Scott Ruthardt.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Geology.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 155 p.
  • 总页数 155
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;
  • 关键词

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