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首页> 外文学位 >Mechanisms and Magnitude of Cenozoic Crustal Extension in the Vicinity of Lake Mead, Nevada and the Beaver Dam Mountains, Utah: Geochemical, Geochronological,Thermochronological and Geophysical Constraints.
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Mechanisms and Magnitude of Cenozoic Crustal Extension in the Vicinity of Lake Mead, Nevada and the Beaver Dam Mountains, Utah: Geochemical, Geochronological,Thermochronological and Geophysical Constraints.

机译：内华达州米德湖和比弗坝山附近的新生代地壳扩展机制和幅度：地球化学，地球年代学，热年代学和地球物理约束。

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摘要

The central Basin and Range Province of Nevada and Utah was one of the first areas in which the existence of widespread low-angle normal faults or detachments was first recognized. The magnitude of associated crustal extension is estimated by some to be large, in places increasing original line lengths by as much as a factor of four. However, rock mechanics experiments and seismological data cast doubt on whether these structures slipped at low inclination in the manner generally assumed. In this dissertation, I review the evidence for the presence of detachment faults in the Lake Mead and Beaver Dam Mountains areas and place constraints on the amount of extension that has occurred there since the Miocene.;Chapter 1 deals with the source-provenance relationship between Miocene breccias cropping out close to Las Vegas, Nevada and their interpreted source at Gold Butte, currently located 65 km to the east. Geochemical, geochronological and thermochronological data provide support for that long-accepted correlation, though with unexpected mismatches requiring modification of the original hypothesis. In Chapter 2, the same data are used to propose a refinement of the timing of ~1.45 Ga anorogenic magmatism, and the distribution of Proterozoic crustal boundaries.;Chapter 3 uses geophysical methods to address the subsurface geometry of faults along the west flank of the Beaver Dam Mountains of southwestern Utah. The data suggest that the range is bounded by steeply inclined normal faults rather than a regional-scale detachment fault. Footwall folding formerly ascribed to Miocene deformation is reinterpreted as an expression of Cretaceous crustal shortening. Fission track data presented in Chapter 4 are consistent with mid-Miocene exhumation adjacent to high-angle normal faults. They also reveal a protracted history dating back to the Pennsylvanian-Permian time, with implications for the interpretation of other basement-cored uplifts in the region.;A key finding of this dissertation is that the magnitude of crustal extension in this region has been overestimated. The pre-extensional width was increased by a factor of two across Lake Mead, through a combination of high-angle normal faulting and strike-slip deformation. Data from the transect across the Beaver Dam Mountains suggest substantially less extension, with the difference accommodated for the most part by displacement on the intervening Las Vegas Valley Shear Zone. The Colorado Plateau-Basin and Range transition zone may be a long-lived tectonic boundary where this assumption may be especially ill-suited.
机译：内华达州和犹他州的中部盆地和山脉省是最早认识到广泛存在的低角度法向断层或分离的地区之一。某些人估计与地壳延伸有关的幅度很大，在某些地方原始线长增加了四倍。但是，岩石力学实验和地震数据使人们怀疑这些结构是否以通常假定的方式在低倾角时打滑。在本文中，我回顾了米德湖和比弗水坝山区存在分离断层的证据，并对中新世以来发生的延伸量施加了限制。;第1章探讨了中新世以来的物源-物源关系。中新世角砾岩在内华达州拉斯维加斯附近种植，其解释源于目前位于东部65公里的Gold Butte。地球化学，年代学和热年代学数据为这种长期接受的相关性提供了支持，尽管存在意想不到的不匹配，需要修改原始假设。在第2章中，使用相同的数据提出了〜1.45 Ga人造岩浆作用的时间的精修以及元古代地壳边界的分布。;第3章使用地球物理方法解决了沿西侧的断层的地下几何形状海狸西南犹他州的水坝山。数据表明，该范围以陡峭倾斜的正断层为界，而不是区域尺度的分离断层。以前归因于中新世变形的下盘褶皱被重新解释为白垩纪地壳缩短的一种表达。第4章介绍的裂变径迹数据与中高新世邻近高角度正断层的发掘一致。他们还揭示了一段可追溯到宾夕法尼亚州-二叠纪时期的悠久历史，对该地区其他以地下为核心的隆升的解释具有重要意义。本论文的一个关键发现是该地区地壳扩展的幅度被高估了。 。通过大角度法向断层和走滑变形的组合，整个米德湖的伸展前宽度增加了两倍。来自比弗水坝山脉的横断面数据表明，延伸范围要小得多，而差异主要是通过中间的拉斯维加斯山谷剪切带上的位移来解决的。科罗拉多高原-盆地和山脉过渡带可能是一个长寿的构造边界，在这个构造边界可能特别不合适。

著录项

  • 作者

    Almeida, Rafael V.;

  • 作者单位

    Columbia University.;

  • 授予单位 Columbia University.;
  • 学科 Geology.;Geochemistry.;Geophysics.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 378 p.
  • 总页数 378
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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