Collaborative Research: Determining the 3D Kinematic Evolution of the Wyoming Laramide, Implications for Processes of Foreland Deformation

前陆变形主要集中在形成不同取向基底拱的地球动力学过程、基底变形及其向盖层转移的机制、与板块边缘应力的关系等方面。该项目将整合怀俄明州Laramide构造的构造、各向异性磁化率（AMS）和古地磁研究，以测试各种前陆变形的构造模型。可测试的模型包括应力方向的时间变化（可能与平板俯冲有关），应力和断层方向的空间变化（可能与基底各向异性有关），以及沿不同取向构造的剪切分量的变化。该项目的结果将进一步提供有关怀俄明州前陆构造圈闭、裂缝系统和断层模式的数据，这将提高对油气储集层和潜在二氧化碳封存地点的了解。最后，这项合作研究将与正在进行的其他造山带的古地磁和构造研究相结合，以比较不同环境下的造山过程，并将产生大量数据集，用于运动学和力学分析中使用的各种应变和古应力方法的统计比较。本次调查的重点将放在怀俄明州前陆显示一系列趋势和变形风格的关键构造上，以及两个地层水平（三叠纪红层和侏罗纪石灰岩），这些地层水平暴露良好，携带原始残余磁化，并包含多种应变标志。通过测量和分析小断层系统的特征来估计古应力模式，通过AMS组构和方解石孪晶分析来估计应变方向，通过钻取定向岩心进行古地磁分析来量化垂直轴旋转的时间和震级。对于选定的暴露良好的表面，将对断裂模式特征进行量化，以测试与褶皱和断层力学的关系。通过整合多个数据集，可以减少每个数据集的局限性。至关重要的是，古地磁数据将与变形结构（小断层、AMS、方解石孪晶和裂缝）和横截面/三维恢复相结合，以量化古应力/应变的垂直轴旋转和时空变化。该项目将在以往研究的基础上提供一个广泛的数据库，以便严格测试拉腊胺前陆变形的运动学模型和力学过程。

First-order outstanding questions regarding foreland deformation center on geodynamic processes that form diverse orientations of basement arches, mechanisms of basement deformation and its transfer to the sedimentary cover, and relationships to plate margin stresses. This project will integrate structural, anisotropy of magnetic susceptibility (AMS), and paleomagnetic studies of Laramide structures in Wyoming to test various tectonic models of foreland deformation. Testable models include, temporal changes in stress directions (possibly associated with flat-slab subduction), spatial variations in stress and fault orientations (potentially associated with basement anisotropy), and varying components of shear along differently oriented structures. Results of this project will further provide data on structural traps, fracture systems, and fault patterns within the Wyoming foreland, which will improve understanding of hydrocarbon reservoirs and potential sites for carbon dioxide sequestration. Finally, this collaborative investigation will be merged with ongoing paleomagnetic and structural studies of other orogens to compare processes of mountain building in different settings, and will generate large data sets for statistical comparisons of various strain and paleostress methods used in kinematic and mechanical analysis.The focus of this investigation will be on key structures that display a range of trends and deformation styles in the Wyoming foreland, and on two stratigraphic levels (Triassic redbeds and Jurassic limestone) that are well exposed, carry primary remanent magnetizations, and contain multiple strain markers. Characteristics of minor fault systems will be measured and analyzed to estimate paleostress patterns, strain orientations will be estimated from AMS fabrics and calcite twin analysis, and oriented cores will be drilled for paleomagnetic analysis to quantify timing and magnitudes of vertical-axis rotations. Characteristics of fracture patterns will be quantified for selected well-exposed surfaces to test relationships to fold and fault mechanics. By integrating multiple data sets, limitations of each set will be reduced. Critically, paleomagnetic data will be combined with deformation fabrics (minor faults, AMS, calcite twins, and fractures) and cross sections/3-D restorations to quantify both vertical-axis rotations and spatial-temporal changes in paleostress/strain. This project will provide an expansive data base, building on previous studies, in order to critically test kinematic models and mechanical processes of Laramide foreland deformation.