Jura-Cretaceous Sinistral Displacement of Terranes Along the Northern Cordilleran Margin

北美地质学最具争议的方面之一是，在晚白垩世-古近纪，由于北美和原始太平洋构造板块之间的汇聚和平移，从加利福尼亚州延伸到阿拉斯加的岩石在多大程度上沿着大陆边缘被南移和北移。一些关系表明流动性有限--地质特征仍保持在它们形成的地方附近。相比之下，其他数据集表明，阿拉斯加、不列颠哥伦比亚省、华盛顿州和俄勒冈州大部分地区的数千公里运输岩石首先向南移动到墨西哥纬度，然后向北移动到目前的位置。整个海岸运输的不确定性阻碍了我们重建北美西部的地质演化和了解位于这些地区的重要能源和矿产资源的起源(和未来的发现)的能力。这个项目的重点是确定从华盛顿州西北部延伸到阿拉斯加南部的断层系统所容纳的南向运动量。除了该项目的科学目标外，该奖项还通过在一个重要学科培训学生来支持重要的社会成果，该学科有助于发展一支多元化的、具有全球竞争力的STEM劳动力队伍。该研究项目还涉及与不列颠哥伦比亚省地质调查局的研究人员合作。该项目涉及对断层系统进行野外和实验室分析，这些断层系统可能容纳了长达1600公里的岩石组合南移。调查人员将进行详细的结构分析，以确定已识别断层上的位移量，绘制已识别断层之间的区域图以评估连续性，并收集将限制运动发生时间的样本。实地研究将把重点放在不列颠哥伦比亚省沿海的断层上，因为这些断层是断层中最著名的部分-它们延伸到阿拉斯加和华盛顿的范围没有受到很好的限制。该项目的科学目标包括：1)检验假设，即这两条断层中的每一条都记录了大约800公里的晚侏罗世-早白垩世左行运动；(2)评估岛状和山间构造地层地体被早白垩世缝合带分隔的替代解释；(3)利用这些新信息来评估目前的科迪勒古地理模型；以及(4)将左行断裂建立为斜向俯冲期间在活动岩浆弧内活动的剪切带的世界级例子。现场和实验室分析将主要由亚利桑那大学的本科生进行，以努力提供机会学习前沿地区的地质制图技术，并在亚利桑那大学激光计时中心(亚利桑那大学)使用最先进的仪器进行地质年代学和地球化学分析。每个学生都将充分参与野外和实验室研究，以便他们能够准备一份手稿出版，其中包括详细的区域地质图，关键构造/侵入关系的描述，大型地质年代学和地球化学数据集，以及广泛意义的解释。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

One of the most controversial aspects of North American geology concerns the degree to which rocks extending from California to Alaska have been transported south and then north along the continental margin due to convergence and translation between the North American and ancestral Pacific tectonic plates during Late Cretaceous-Paleogene time. Some relationships suggest limited mobility - geologic features remain close to where they formed. In contrast, other data sets suggest thousands of kilometers of transport - rocks in much of Alaska, British Columbia, Washington, and Oregon first moved south to the latitude of Mexico, and then moved back north to their present positions. The uncertainty in coast-wide transport hinders our ability to reconstruct the geologic evolution of western North America and to understand the origin (and future discovery) of important energy and mineral resources located in these regions. This project focuses on determining the amount of southward motion accommodated on fault systems that extend from northwestern Washington to southern Alaska. In addition to the scientific goals of the project, the award is supporting important societal outcomes by training students in an important discipline that is contributing to the development of a diverse, globally competitive STEM workforce. The research project also involves collaboration with researchers from the British Columbia Geological Survey.This project involves field and laboratory analysis of fault systems that may have accommodated up to 1600 km of southward motion of rock assemblages. The investigators will conduct detailed structural analyses to determine the amounts of displacement on recognized faults, map areas between recognized faults to evaluate continuity, and collect samples that will constrain when motion occurred. Field studies will focus on faults in coastal British Columbia given that these are the best-known segments of the faults - their extensions into Alaska and Washington are not well constrained. The scientific objectives of the project include: 1) testing the hypotheses that each of these two fault record approximately 800 kilometers of Late Jurassic-Early Cretaceous sinistral motion, (2) evaluating the alternative interpretation that the Insular and Intermontane tectonostratigraphic terranes are separated by an Early Cretaceous suture zone, (3) using this new information to evaluate current models for Cordilleran paleogeography, and (4) establishing the sinistral faults as world-class examples of shear zones operating within an active magmatic arc during oblique subduction. Field and laboratory analyses will be conducted in large part by undergraduate students at the University of Arizona in an effort to provide opportunities to learn techniques of geologic mapping in a frontier area, and to perform geochronologic and geochemical analyses using state-of-the-art instruments at the Arizona LaserChron Center (University of Arizona). Each student will be sufficiently engaged in the field and laboratory studies that they will be able to prepare a manuscript for publication that includes detailed and regional geologic maps, descriptions of critical structural/intrusive relations, large geochronologic and geochemical data sets, and interpretations of broad significance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.