Collaborative Research: Testing Models of Mesozoic Arc Collision and Accretion in the Northwest U.S. Cordillera, Eastern Oregon, Using Sedimentary Provenance and Basin Analysis

尽管有丰富的研究历史，但对美国西部科迪勒拉侏罗纪地壳变形的板块构造背景和区域控制仍然知之甚少。已有研究推测侏罗纪科迪勒拉边缘为非碰撞的安第斯型弧沟系统，但俄勒冈州东部和内华达州西北部新出现的构造和地层数据与晚三叠世至晚侏罗世大型碰撞盆地的长期弧弧碰撞和生长模式一致。俄勒冈州东部的蓝山省为评估弧碰撞在科迪勒构造中的作用提供了一个极好的试验场。该地区含有古生代和中生代岩石，代表了两个被肢解的岩浆弧、一个介于其间的大洋俯冲杂岩和一个被称为“Izee盆地”的厚厚的沉积重叠组合。Izee盆地地层记录了晚三叠世至晚侏罗世时期影响俄勒冈州及其周边地区的构造过程和事件。这项研究正在检验一种新的假说，即蓝山省是经过长期的弧-弧碰撞、弧形地体的融合、大型海洋碰撞盆地的生长，最后这些地体向北美西部逆冲和初始吸积而形成的。PI正在通过对晚三叠世至晚侏罗世地层、沉积物源和盆地演化的详细研究来检验碰撞盆地假说。主要的假设对页岩中的微量元素和钕同位素特征、古砂岩中的碎屑锆石年龄群体和骨架矿物学以及沉积岩中的区域地层关系做出了具体的预测。综合物源和地层分析将提供有关盆地演化和造山的新信息，使我们能够区分构造假说，并评估弧碰撞和吸积在侏罗纪科迪勒造山中的作用。这项研究解决了长期存在的问题，即中生代时期导致北美西部大陆地壳生长和组装的边界条件和驱动力。该项目正在为俄勒冈大学和华盛顿州大学的研究生和本科生的培训和教育做出贡献。学生直接参与现场和实验室方法、研究方法和关键问题的解决，随着他们进入研究生和本科论文阶段。所有参与者都积极参与与古生物学家、构造地质学家、岩石学家和地球物理学家的合作，他们正在努力破译蓝山的构造演化。区域。这为科学发现创造了新的机会，通过多学科研究以及大学、美国地质调查局和国家机构的广泛专业人员和学生之间的相互合作。

The plate-tectonic setting and regional controls on Jurassic crustal deformation in the western U.S. Cordillera remain poorly understood, despite a rich history of research related to this question. Some studies have inferred a non-collisional Andean-type arc-trench system for the Jurassic Cordilleran margin, but emerging structural and stratigraphic data from eastern Oregon and NW Nevada are consistent with a model for protracted arc-arc collision and growth of a large collisional basin during Late Triassic to Late Jurassic time. The Blue Mountains Province of eastern Oregon provides an excellent testing ground for evaluating the role of arc collision in Cordilleran tectonics. This region contains Paleozoic and Mesozoic rocks that represent two dismembered magmatic arcs, an intervening oceanic subduction complex, and a thick sedimentary overlap assemblage known as the "Izee basin". Izee basinal strata contain a record of tectonic processes and events that affected Oregon and surrounding areas during Late Triassic to Late Jurassic time. This research is testing a a new hypothesis that the Blue Mountains Province evolved by protracted arc-arc collision, amalgamation of arc terranes, growth of a large marine collisional basin, and finally thrusting and initial accretion of these terranes to western North America. The PIs are testing the collisional-basin hypothesis through a detailed study of Late Triassic to Late Jurassic stratigraphy, sedimentary provenance, and basin evolution. The leading hypothesis makes specific predictions about trace-element and Neodymium-isotopic signatures in shales, detrital zircon age populations and framework mineralogy in ancient sandstones, and regional stratigraphic relationships in sedimentary rocks. Integrated provenance and stratigraphic analysis will provide new information about basin evolution and mountain building that will allow us to discriminate between tectonic hypotheses and evaluate the role of arc collision and accretion in Cordilleran mountain building during Jurassic time. The research addresses long-standing questions about the boundary conditions and driving forces that led to the growth and assembly of continental crust in western North America during Mesozoic time. The project is contributing to the training and education of graduate and undergraduate students at the University of Oregon and Washington State University. Students are directly involved in field and laboratory methods, research methodology, and critical problem solving as they progress toward graduate and undergraduate theses. All participants are actively engaged in collaborations with paleontologists, structural geologists, petrologists and geophysicists, who are working to decipher the tectonic evolution of the Blue Mountains. region. This is creating new opportunities for scientific discovery through multidisciplinary research and mutual cooperation among a wide range of professionals and students at universities, the U.S. Geological Survey, and state agencies.