Collaborative Research: Three-Dimensional Kinematic History of the Wyoming Salient: Implications for Development of Curved Orogens

合作研究：怀俄明凸起的三维运动学历史：对弯曲造山带发育的影响

• 批准号: 0408653
• 负责人: W.A. Yonkee
• 金额: --
• 依托单位: Weber State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0408653&HistoricalAwards=false
• 关键词: Collaborative; Research; Three; Dimensional; Kinematic

Most mountain belts display varying degrees of curvature over a range of scales, recording complex, three-dimensional deformation histories. However, despite their ubiquitous occurrence, few examples exist where deformation histories and processes responsible for orogenic curvature have been adequately quantified from geologic evidence. These histories are embedded in regional structural trends, paleomagnetic directions, mesoscopic structures, and grain-scale fabrics of deformed rocks. The Utah-Idaho-Wyoming salient of the Sevier orogenic belt is an ideal location to study processes that produce curvature over a range of scales. Regional trends of major thrust faults and folds curve through 90 degrees from the north to south end of the salient, with additional local curvature near cross-strike transfer zones. Rocks in the salient also carry multiple paleomagnetic components and display systematic suites of mesoscopic and microscopic structures (including cleavage, minor folds, minor fault networks, and deformed fossils), providing a record of rotations and internal strain within individual thrust sheets. Initial studies in the Wyoming salient reveal both primary pre-thrusting and secondary syn-folding paleomagnetic components that record complex rotation histories related to thrust curvature. Initial studies also reveal broadly consistent regional strain patterns, with widespread layer-parallel shortening at high angles to thrust trends, minor tangential extension parallel to thrust trends, and minor wrench shear. Calcite-twin strains, which accumulated during early layer-parallel shortening prior to large-scale thrusting, provide another reference frame that records locally significant rotations. Ongoing work is focused on combined paleomagnetic and structural studies of three 'swaths' located in the southern, central, and northern frontal parts of the salient, and on two stratigraphic levels (Jurassic Twin Creek Limestone and redbeds of the Triassic Ankareh Formation) that are well exposed, carry multiple magnetizations, and contain multiple strain markers. Analysis of slip lineation data from major thrust faults and construction of two-dimensional cross sections indicate that thrust transport directions change overall from ENE in the northern part to ESE in the southern part of the salient, and fault slip magnitude decreases toward the north and south ends of the salient. Three-dimensional cross sections, constrained by abundant seismic data, and incorporating new strain and rotation data from this study, are being constructed to develop a robust kinematic model of the salient. The model will be used to identify controlling mechanisms responsible for mountain belt curvature, including variations in stratigraphic thicknesses, strength changes along faults, motion of indentors, and foreland buttress effects. This investigation addresses several fundamental questions concerning the evolution of mountain belts. (1) What are the relations between rotations, strain, changes in thrust fault slip, and salient curvature? (2) What are the consequences of incorporating strain and rotation data into three-dimensional models of orogenic belts? (3) What factors are most important in developing curved mountain belts and how can these factors be best identified? Ultimately, findings from the Wyoming salient will be compared with similar ongoing studies of other curved mountain belts, providing an array of viable models for the development of curved orogens. Lastly, inclusion of strain and rotation data into three-dimensional restorable deformation models should improve our general understanding of hydrocarbon accumulations in fold-thrust belts.

大多数山带在一系列尺度上显示出不同程度的曲率，记录复杂的三维变形历史。 但是，尽管出现了无处不在的情况，但很少有例子是从地质证据中充分量化了导致造山曲率的变形历史和过程的例子。 这些历史嵌入了区域结构趋势，古磁方向，介观结构和变形岩石的晶尺度织物中。 Sevier造山带的犹他州 - 爱和异教徒的显着性是研究在一系列尺度上产生曲率的理想场所。 从突出的北端到南端的90度的主要推力断层和折叠曲线的区域趋势，在跨撞式转移区域附近额外的局部曲率。 显着的岩石还携带多种古磁成分，并显示介观和显微镜结构的系统套件（包括裂解，较小的折叠，次要断层网络和变形的化石），提供了单个推力板内的旋转和内部应变的记录。 怀俄明州显着的初步研究揭示了主要的预防和二级合成的古磁成分，这些成分记录了与推力曲率相关的复杂旋转历史。 最初的研究还揭示了广泛一致的区域应变模式，并以高角度到推力趋势的广泛层平行缩短，平行于推力趋势的小切向切向延伸和较小的扳手剪切。 在大规模推力之前，在早期层平行的缩短过程中积累的方解石双重菌株提供了另一种参考框架，以记录局部重要的旋转。正在进行的工作集中于位于显着的南部，中部和北部额叶的三个“缠绕”的古磁和结构研究，以及两个地层层次（侏罗纪双溪石灰岩和三叠纪Ankareh形成的侏罗纪双溪石灰岩和红床），这些含量很好地暴露，携带多个磁磁标记。 分析来自重大推力断层的滑移线数据和二维横截面的构建表明，推力传输方向从北部的ENE到显着的南部的ESE变化，并且断层滑移幅度降低了向突出的北端和南端。 由大量地震数据限制，并结合了本研究的新菌株和旋转数据的三维横截面，以开发出强大的显着运动学模型。 该模型将用于识别负责山带曲率的控制机制，包括地层厚度的变化，断层沿断层的强度变化，固定器的运动以及前陆支撑效应。 这项调查解决了有关山带演变的几个基本问​​题。 （1）旋转，应变，推力断层滑动的变化和显着曲率之间有什么关系？ （2）将应变和旋转数据纳入三维造山带模型的后果是什么？ （3）哪些因素在开发弯曲的山带方面最重要，如何最好地确定这些因素？ 最终，将怀俄明州显着的发现与对其他弯曲山带进行的类似研究进行比较，为弯曲的Ogens的发展提供了一系列可行的模型。 最后，将应变和旋转数据纳入三维可再生变形模型，应提高我们对折叠式带状带中碳氢化合物积累的一般理解。