Collaborative Research: RUI: Continental-Scale Study of Jura-Cretaceous Basins and Melanges along the Backbone of the North American Cordillera-A Test of Mesozoic Subduction Models

合作研究：RUI：北美科迪勒拉山脊沿线汝拉-白垩纪盆地和混杂岩的大陆尺度研究——中生代俯冲模型的检验

• 批准号: 2346567
• 负责人: Devon Orme
• 金额: $ 18.48万
• 依托单位: Montana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2346567&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Continental; Scale

The geologic processes that formed the North American Cordillera, mountains that extend from western Mexico to Alaska, are disputed. These mountain ranges and neighboring basins (such as the Sierra Nevada and Great Valley basin within California) are conventionally interpreted to have formed due to eastward subduction of an oceanic plate beneath the western margin of the North American continent. Recent studies challenge this model and propose that much of the western Cordillera formed as an archipelago above westward subduction of an oceanic plate far from the margin of North America. In this alternative model, the archipelago became part of the Cordillera when the North American continent collided with the archipelago. This continental-scale study will test these models along four east-west transects across the western Cordillera in central Alaska, SE Alaska, British Columbia, and California. The project will provide support for four PIs, two of whom are female, the PhD work of three graduate students, and each PI’s commitment to provide undergraduate students with authentic field and laboratory experiences. The research methods are ideal for training undergraduate students to think across a range of spatial and temporal scales in the context of field observations and quantitative analyses, and undergraduate students will benefit from near-peer mentoring by graduate students. The researchers will also lead a multi-day field trip for Native American students centered on the connections between geologic processes that formed western North America and the homelands of Indigenous communities. The research addresses the fundamental problem of determining subduction polarity along ancient convergent margins. This project will couple the study of mélange belts with basin strata, and integrate the results along the hypothesized continental-scale suture within the North American Cordillera. This collaborative project will evaluate 1) the age and provenance of mélange belts, 2) the basins’ structural and sedimentological configuration (including inboard and outboard contacts), 3) the timing of basin formation and subsequent collapse, and 4) basin and mélange provenance comparison in the context of east-dipping versus west-dipping subduction. Analysis of the basin strata and adjacent mélange belts using detrital zircon analysis (U-Pb, Lu-Hf, and trace element geochemistry), sandstone petrography, and whole-rock Sm-Nd isotopic analysis and trace-element geochemistry will provide a continental-scale test of proposed models to better understand the Mesozoic development of the North American Cordillera. This project will also refine methods for establishing the geometry and timing of convergent margin systems in other orogens, particularly pre-Mesozoic systems for which tomographic information is not available.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.

形成北美科迪勒拉山脉的地质过程是有争议的，这些山脉从墨西哥西部延伸到阿拉斯加。这些山脉和邻近的盆地（如内华达州山脉和加州境内的大峡谷盆地）通常被解释为是由于北美大陆西部边缘下的海洋板块向东俯冲而形成的。最近的研究挑战了这一模型，并提出西科迪勒拉山脉的大部分地区是在远离北美边缘的海洋板块向西俯冲的过程中形成的群岛。在这个替代模型中，当北美大陆与群岛相撞时，群岛成为科迪勒拉山脉的一部分。这个大陆规模的研究将测试这些模型沿沿着四个东西向的横断面横跨西部科迪勒拉在阿拉斯加中部，阿拉斯加东南部，不列颠哥伦比亚省，和加州。该项目将为四名PI提供支持，其中两名是女性，三名研究生的博士工作，以及每个PI为本科生提供真实的实地和实验室经验的承诺。研究方法是理想的训练本科生认为在一系列的空间和时间尺度的背景下，实地观察和定量分析，和本科生将受益于近同行的指导研究生。研究人员还将带领美洲原住民学生进行为期多日的实地考察，重点是形成北美西部和土著社区家园的地质过程之间的联系。这项研究解决了确定沿着古会聚边缘俯冲极性的基本问题。该项目将把混杂岩带的研究与盆地地层结合起来，并将结果沿北美科迪勒拉山脉内的假设大陆尺度缝合线进行沿着整合。该合作项目将评估1）混杂岩带的年龄和物源，2）盆地的结构和沉积学配置（包括内侧和外侧接触），3）盆地形成和随后坍塌的时间，以及4）在东倾和西倾俯冲背景下的盆地和混杂岩物源比较。 使用碎屑锆石分析（U-Pb、Lu-Hf和微量元素地球化学）、砂岩岩相学、全岩Sm-Nd同位素分析和微量元素地球化学对盆地地层和邻近混杂岩带进行分析，将为所提出的模型提供一个大陆规模的测试，以更好地了解北美科迪勒拉的中生代发展。该项目还将改进其他造山带中收敛边缘系统的几何形状和时间确定方法，特别是断层成像信息不可用的前中生代系统。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进行评估，被认为值得支持。