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首页> 外文学位 >Deformation processes in orogenic wedges: New methods and application to Northwestern Washington State.
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Deformation processes in orogenic wedges: New methods and application to Northwestern Washington State.

机译：造山楔的变形过程：新方法及其在西北华盛顿州的应用。

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摘要

Permanent deformation records aspects of how material moves through a tectonic environment. The methods required to measure deformation vary based on rock type, deformation process, and the geological question of interest. In this thesis we develop two new methods for measuring permanent deformation in rocks.;The first method uses the autocorrelation function to measure the anisotropy present in two-dimensional photomicrographs and three-dimensional X-ray tomograms of rocks. The method returns very precise estimates for the deformation parameters and works best for materials where the deformation is recorded as a shape change of distinct fabric elements, such as grains. Our method also includes error estimates. Image analysis techniques can focus the method on specific fabric elements, such as quartz grains.;The second method develops a statistical technique for measuring the symmetry in a distribution of crystal orientations, called a lattice-preferred orientation (LPO). We show that in many cases the symmetry of the LPO directly constrains the symmetry of the deformation, such axial flattening vs. pure shear vs. simple shear. In addition to quantifying the symmetry, the method uses the full crystal orientation to estimate symmetry rather than pole figures. Pole figure symmetry can often be misleading. This method works best for crystal orientations measured in samples deformed by dislocation creep, but otherwise can be used on any mineral without requiring information about slip systems.;In Chapter 4 we show how deformation measurements can be used to inform regional tectonic and orogenic models in the Pacific Northwestern United States. A suite of measurements from the Olympic Mountains shows that uplift and deformation of the range is consistent with an orogenic wedge model driven by subduction of the Juan de Fuca plate, and not northward forearc migration of the Oregon block.;The deformation measurements also show that deformation within the Olympic Mountains is essentially two-dimensional. We use this constraint to develop a suite of orogenic deformation models that use slab height and erosion rate data as boundary conditions. We use the models to show that influx of sediments distributed along an accretionary front can greatly reduce deformation required to maintain wedge taper. Due to the two-dimensional nature of deformation in the Olympics, a series of two-dimensional transects across the peninsula provides an approximation for non-elastic deformation across the Peninsula. We show how the shallow slab height and deeper exhumation at the core of peninsula led to the domal structure of the Olympics. This model also explains the counter-clockwise vertical axis rotations north of the peninsula, and clockwise rotations south of the peninsula through horizontal shear, similar to opening a gate. Finally, the horizontal surface velocities predicted by the models suggests that up to 15% of GPS velocities may reflect non-elastic, permanent translation of material towards the rear of the wedge.
机译：永久变形记录了材料如何在构造环境中运动的各个方面。测量变形所需的方法因岩石类型，变形过程和感兴趣的地质问题而异。本文研究了两种测量岩石永久变形的新方法。第一种方法是使用自相关函数测量岩石的二维显微照片和三维X射线断层照片中的各向异性。该方法对变形参数返回非常精确的估计值，并且最适合将变形记录为不同织物元素（例如颗粒）的形状变化的材料。我们的方法还包括误差估计。图像分析技术可以将方法聚焦于特定的织物元素，例如石英颗粒。第二种方法开发了一种统计技术，用于测量晶体取向分布中的对称性，称为晶格优先取向（LPO）。我们表明，在许多情况下，LPO的对称性直接限制了变形的对称性，例如轴向展平与纯剪切与简单剪切。除了量化对称性之外，该方法还使用完整的晶体取向来估计对称性而不是极图。极图对称性经常会产生误导。这种方法最适合于由位错蠕变变形的样品中测量的晶体取向，但在不需要滑移系统信息的情况下，也可以用于任何矿物。在第4章中，我们说明了如何使用形变测量来为区域构造和造山模型提供信息。美国西北太平洋。一组来自奥林匹克山的测量结果表明，该范围的隆升和变形与胡安·德·富卡板块俯冲驱动的造山楔模型一致，而不是俄勒冈块向北前移的结果。奥林匹克山脉内部的变形基本上是二维的。我们使用此约束条件来开发一套造山变形模型，该模型使用板坯高度和侵蚀速率数据作为边界条件。我们使用模型表明，沿增生锋线分布的沉积物涌入可大大减少保持楔形锥度所需的变形。由于奥运会中变形的二维性质，整个半岛上的一系列二维样条线为半岛上的非弹性变形提供了近似值。我们展示了半岛中心的浅层平板高度和更深的掘尸如何导致奥林匹克运动的消极结构。该模型还解释了半岛水平方向沿垂直轴的逆时针旋转，以及水平剪切作用在半岛南部方向沿顺时针的旋转，类似于打开闸门。最后，模型预测的水平面速度表明，高达15％的GPS速度可能反映了材料向楔形物后部的非弹性，永久性平移。

著录项

  • 作者

    Thissen, Christopher J.;

  • 作者单位

    Yale University.;

  • 授予单位 Yale University.;
  • 学科 Geology.;Geophysics.;Continental dynamics.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 244 p.
  • 总页数 244
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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