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

北美地质学最有争议的方面之一是，由于晚白垩世-古近纪时期北美和太平洋构造板块之间的会聚和平移，从加州到阿拉斯加的岩石沿着大陆边缘向南然后沿着向北迁移的程度。一些关系表明有限的流动性-地质特征仍然接近它们形成的地方。相比之下，其他数据集显示，阿拉斯加、不列颠哥伦比亚省、华盛顿和俄勒冈州的岩石先是向南移动到墨西哥的纬度，然后又向北移动到现在的位置。沿岸运输的不确定性阻碍了我们重建北美西部地质演化的能力，也阻碍了我们了解这些地区重要能源和矿产资源的起源（和未来发现）。该项目的重点是确定从华盛顿西北部延伸到阿拉斯加南部的断层系统所容纳的向南运动量。除了该项目的科学目标外，该奖项还通过在一个重要学科中培训学生来支持重要的社会成果，该学科有助于发展多元化，具有全球竞争力的STEM劳动力。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的合作，该项目涉及对断层系统的实地和实验室分析，这些断层系统可能容纳了长达1 600公里的岩石组合向南运动。调查人员将进行详细的结构分析，以确定已识别断层的位移量，绘制已识别断层之间的区域以评估连续性，并收集将在运动发生时进行约束的样本。实地研究将侧重于沿海不列颠哥伦比亚省的断层，因为这些断层是最著名的断层段--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）检验这两个断层中的每一个都记录了大约800公里的晚侏罗世-早白垩世左旋运动的假设，（2）评估岛屿和山间构造地层断层被早白垩世缝合带分开的替代解释，（3）利用这些新信息评估目前的科迪勒纳古地理模型，（4）确立左旋断裂为斜向俯冲过程中活动岩浆弧内剪切带的世界级范例。野外和实验室分析将主要由亚利桑那大学的本科生进行，以提供机会学习在前沿地区绘制地质图的技术，并在亚利桑那大学的亚利桑那激光年代中心使用最先进的仪器进行地质年代学和地球化学分析。 每个学生将充分参与实地和实验室研究，他们将能够准备出版手稿，其中包括详细的区域地质图，关键结构/侵入关系的描述，大型地质年代学和地球化学数据集，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准。

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.