通过现场数据和模拟沙盒建模相结合的办法探索出了一条凸槽结的运动史
Summary
Kinematic histories of fold-thrust belts are typically based on careful examinations of high-grade metamorphic rocks within a salient. We provide a novel method of understanding fold-thrust belts by examining salient-recess junctions. We analyze the oft-ignored upper crustal rocks using a combined approach of detailed fault analysis with experimental sandbox modeling.
Abstract
Within fold-thrust belts, the junctions between salients and recesses may hold critical clues to the overall kinematic history. The deformation history within these junctions is best preserved in areas where thrust sheets extend from a salient through an adjacent recess. We examine one such junction within the Sevier fold-thrust belt (western United States) along the Leamington transverse zone, northern Utah. Deformation within this junction took place by faulting and cataclastic flow. Here, we describe a protocol that examines these fault patterns to better understand the kinematic history of the field area. Fault data is supplemented by analog sandbox experiments. This study suggests that, in detail, deformation within the overlying thrust sheet may not directly reflect the underlying basement structure. We demonstrate that this combined field-experimental approach is easy, accessible, and may provide more details to the deformation preserved in the crust than other more expensive methods, such as computer modeling. In addition, the sandbox model may help to explain why and how these details formed. This method can be applied throughout fold-thrust belts, where upper-crustal rocks are well preserved. In addition, it can be modified to study any part of the upper crust that has been deformed via elastico-frictional mechanisms. Finally, this combined approach may provide more details as to how fold-thrust belts maintain critical-taper and serve as potential targets for natural resource exploration.
Introduction
褶皱冲断带是由salients（或段），其中在毗邻salients推力纸张由凹槽或横向区1,2,3脱钩的。从突出到凹陷的过渡可能会明显复杂，涉及到结构的多方面的套件，可以存放重要线索褶皱冲断带的发展。在本文中，我们仔细检查一个凸槽交界处，使用多尺度的现场数据和沙箱模型的组合，以更好地了解变形如何容纳褶皱冲断带之内。
中央犹他州段和利明横向区域的交界处是理想的天然实验室用于研究凸凹接合部有几个原因（ 图1）。首先，将段内露出的岩石继续，不中断，进入横向区4。所以，变形图案可以连续跟踪和穿过结比较。小号的Econd，岩石基本上是单矿物，所以在故障模式的变化是不是单元内的非均质性的结果，而是反映了总体折叠和研究区域4内推压。第三，elastico-摩擦机制，如碎裂流，辅助变形整个场区，允许的尺度故障模式4直接比较。最后，总的输送方向保持沿着段和横向区域的长度连续的;因此，在缩短方向的变化不影响保留变形图案4。所有这些因素最小化的可能已影响到沿区段和横向区域中的变形的变量数。作为结果，我们推测，保留结构形成，主要是因为在底层基底几何学5的变化。
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图1.索引图的例子。美国西部的塞维尔褶皱冲断带，呈现出大salients，段凹陷和横向的区域。由图2中方框区域（从伊斯马特·和Toeneboehn 7修改）表示。 请点击这里查看更大的版本这个数字。
折叠和中央犹他州段和横利明顿区域内逆冲，发生在深度<15公里处， 即 elastico-摩擦制度，其中主要的变形发生由露头尺度范围内（<1米）断层和碎裂流4,6 。由于推力板的运输和折叠发生主要是由elastico-摩擦的机制，我们预测了详细的故障分析可提供进一步洞察利明顿的横向区域，次的运动历史 Ë底层地下室几何。为了检验这一假设，我们已收集并分析中央犹他州段的北部分内和整个利明横向区（ 图2）中的岩石保存故障模式。
图2.宏观尺度地形图的实施例。在图1中方框区域的上色浮雕地形图。4区域是由白色实线分开。元古宙球童峡谷石英岩（PCC）之间的床上用品的接触，相互元古代石英岩（PCM）和寒武纪Tintic石英岩（CT）所示。虚线显示山脉在此区域内的趋势。站点位置显示有编号的黑色方块。一阶线理都用实灰线（从伊斯马特·和Toeneboehn 7修改）。ftp_upload / 54318 / 54318fig2large.jpg“目标=”_空白“>点击此处查看该图的放大版本。
沙箱进行了实验来比较，和补充，故障数据。阿推块沙箱模型，额叶和倾斜坡道，被用来帮助我们保留在结构的分析，和周围的横向利明顿区（ 图3），7。这种方法的目标是四倍：1）确定尺度故障模式是一致的，2）确定所述沙箱模型支持并解释现场数据，3）确定如果沙箱模型提供在不属于结构的更多细节在现场观察到的，和4）评价该组合场实验方法是否是有用和容易复制。
图3的推块M实施例奥德尔。照片空沙箱模式。南部斜坡额叶（SFR），斜斜坡（OR），北斜前方（NFR），以及四个区域（1-4）被标记（由伊斯马特·和Toeneboehn 7修改）。 请点击此处查看大图这个数字。
Protocol
Representative Results
Discussion
在塞维尔褶皱冲断带的中部犹他州段，其北界，在利明顿的横向区域作为理想的天然实验室，研究凸槽结（ 图1）。沿着这条交界处，输送方向保持恒定，并且推力片是跨过该结不间断，所以唯一变量是底层地下室几何5。
这里，我们提出通过组合与推块沙箱模型，它复制场区的大型几何现场收集多尺度故障数据以分析这种类型的凸凹结的方法。沙箱模型?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
We thank Erin Bradley and Liz Cole for their assistance in the field. Field work, thin-section preparation and material for the sandbox model was supported by Franklin & Marshall College’s Committee on Grants.
Materials
| fiberboard | Any | NA | |
| finishing lacquer | Any | NA | |
| epoxy | Epoxy technology | Parts A and B: 301-2 2LB | best if warmed to 80º – 125º. If warming is not possible, it will cure fine, it will just take 1 week, rather than 1 day. |
| ramp wood-pine | Any | NA | |
| painters tape | Any | NA | |
| rabbit joints | Any | NA | |
| countersunk fasteners | Any | NA | |
| sand paper | Any | NA | |
| play sand | Any | NA | best if homogenous grain size, ~0.5mm |
| food coloring | Any | NA | best to use one color and a dark color |
| plastic mesh/grid | Any | NA | |
| square cross oins | Any | NA | |
| crank screw | Any | NA | |
| crank handle | Any | NA | |
| sheet metal | Any | NA | |
| dividers bars | Any | NA |
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