Collaborative Research: RUI: Provenance and Paleomagnetic Analysis of the Ochoco Basin: A Window into Late Cretaceous Paleogeography

合作研究：RUI：奥乔科盆地的物源和古地磁分析：了解晚白垩世古地理的窗口

• 批准号: 1450974
• 负责人: Kathleen Surpless
• 金额: $ 15.09万
• 依托单位: Trinity University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2018-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1450974&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Provenance; Paleomagnetic

The western margin of the North American continent developed through the process of accretion of distinct tectonic terranes of diverse origin due to the oblique subduction of the Farallon plate beneath the North American plate during the Mesozoic. A consequence of this process has been the proposed translation of accreted terranes northward through time to their present-day locations. The extent to which this process has occurred and the proposed timing and magnitude of translation has been an ongoing controversy that has been debated with the geologic community for many years. The goal of this research is address this long-standing scientific controversy using a combination of independent techniques that involve determining the provenance of Late Cretaceous sedimentary rocks from the Blue Mountains and related areas in east-central Oregon using isotopic dating methods, combined with analysis of the paleomagnetic signature contained within those rocks. The provenance analysis will contribute information regarding the potential origin of those rocks with those of similar age elsewhere in North America and the paleomagnetic signature will contribute information regarding the paleolatitude at which these rocks formed. These data will contribute to a better understanding of the geologic evolution of the western North American plate margin. In addition to the research objectives of the proposed study, the project is contributing to the training of ten undergraduate students from two universities and a graduate student in an important STEM discipline and the broadening of participation of underrepresented groups in the earth sciences. The students will be involved in a collaborative team environment that will help them develop analytical and problem solving skills that will make them more competitive for and better prepared to succeed in graduate programs and careers; such training will contribute to important national priorities in terms of STEM research and education. Results of the research will be used in classroom curricula, and the principal investigators and their students will contribute information that will be shared with the National Park Service John Day Fossil Beds National Monument. Results of the research will be disseminated through presentations at professional society meetings and through the peer-reviewed scientific literature; the data will be archived and made available through web-based community databases.The North American Cordilleran margin developed through terrane accretion throughout Mesozoic time, with oblique deformation resulting in dextral translation of many terranes. Significant questions regarding the timing and magnitude of proposed translation remain unresolved, and these uncertainties hinder further understanding of the Cretaceous paleogeography and tectonic history of this margin. The proposed project will utilize complimentary approaches to address some of these questions through study of Late Cretaceous sedimentary rocks of the Blue Mountains in east-central Oregon. The principal investigators propose to integrate detailed provenance analysis with extensive paleomagnetic analysis of Late Cretaceous clastic sedimentary rocks of the Mitchell Inlier and related sedimentary rocks elsewhere in the Blue Mountains to test if these sedimentary rocks were part of a single Ochoco basin system deposited on the Blue Mountains, or if the Mitchell Inlier was a separate forearc sliver, with a tectonic history distinct from the rest of the Blue Mountains and other Late Cretaceous sediments. If there was one large Ochoco basin that was linked to the Blue Mountains during deposition, then our robust paleomagnetic analysis of sedimentary rocks, combined with detailed provenance analysis, will better constrain the paleolatitude of the combined Ochoco basin and Blue Mountains using independent and complimentary data sets. Alternatively, our results may suggest that the Mitchell Inlier and possibly a subset of smaller sedimentary inliers were separate from the Blue Mountains during Cretaceous time, requiring the presence of now-covered large-scale fault system(s) between Mitchell and the Blue Mountains and limiting the amount of dextral translation accommodated on shear zones east of the Blue Mountains. The study will provide robust constraints on the paleolatitude of these Cretaceous rocks, and also provide a test of existing tectonic models and the predictions of these models with respect to potential correlations between Ochoco rocks, the Hornbrook Formation, and other Cretaceous basins. The project will directly address a long-standing debate in Cordilleran tectonics regarding the magnitude and timing of terrane translation by combining provenance and paleomagnetic analysis of well-bedded sedimentary rocks to reconstruct Late Cretaceous paleogeography. The Late Cretaceous sedimentary rocks in the Blue Mountains region provide an ideal opportunity to test several ideas proposed for the paleogeography and tectonic affinity of the Blue Mountains and related terranes using independent and complimentary methods. Furthermore, the large paleomagnetic dataset obtained will allow the application of three independent methods for evaluation and correction for paleomagnetic inclination error in magnetite-bearing clastic sediments. Finally, determining the well-constrained paleogeography of marginal basins such as we propose here will better enable the evidence of uplift and denudation obtained from thermochronology of detrital minerals of a given basin to be tied to a specific location within the North American Cordillera, potentially fostering critical advances in our understanding of the North American Cordillera.

北美大陆的西部边缘是由于中生代期间在北美板块下方的法拉隆板块的倾斜俯冲而产生的各种起源的不同构造地层的过程。这一过程的结果是，随着时间的推移，拟议的塑造台境的拟议翻译到当今的地点。这一过程的发生程度以及提议的时机和翻译规模一直是一个持续的争议，与地质社区辩论了很多年。这项研究的目的是使用独立技术的结合来解决这一长期存在的科学争议，这些技术涉及确定俄勒冈州东部俄勒冈州蓝山脉和相关区域的白垩纪晚期沉积岩石的出处，并结合了对这些岩石中包含的古磁标志的分析。出处分析将贡献有关这些岩石与北美其他地方相似年龄的潜在起源的信息，而古磁性签名将贡献有关这些岩石形成的古显着性的信息。这些数据将有助于更好地理解北美板块边缘的地质演化。除了拟议的研究的研究目标外，该项目还为来自两所大学的十个本科生和一名重要的茎学科研究生的培训做出了贡献，并扩大了地球科学中代表性不足的群体的参与。学生将参与一个协作团队的环境，这将帮助他们发展分析和解决问题的技能，从而使他们更有竞争力，并准备好在研究生课程和职业中取得成功；这种培训将在STEM研究和教育方面有助于国家的重要优先事项。该研究的结果将用于课堂课程，主要研究人员及其学生将贡献与国家公园服务约翰·戴化石床国家纪念碑共享的信息。研究结果将通过专业社会会议上的演讲以及经过同行评审的科学文献来传播；数据将通过基于Web的社区数据库进行存档和提供。北美山脉的边缘通过整个中生代时间通过地层增生而发展，并具有倾斜的变形，导致许多底层的右旋翻译。关于拟议翻译的时间和大小的重大问题仍未解决，这些不确定性阻碍了对这个边缘的白垩纪古地理和构造历史的进一步理解。拟议的项目将通过研究俄勒冈州东部的蓝山脉后期的白垩纪沉积岩来解决这些问题中的一些问题。首席研究人员建议将详细的出处分析与米切尔（Mitchell）近端的白垩纪碎屑沉积岩石的大量古磁分析整合在一起，米切尔（Mitchell蓝色山脉和其他晚白垩纪沉积物。如果有一个与蓝山脉相关的大型Ochoco盆地，那么我们对沉积岩的强大古磁分析，结合了详细的出处分析，将更好地限制使用独立和互补数据集的Ochoco盆地和蓝山的古质量。另外，我们的结果可能表明，米切尔（Mitchell）陷入困境和可能的一部分较小的沉积物嵌入式体在白垩纪时间与蓝山分开，需要在米切尔（Mitchell）和蓝山脉（Mitchell）和蓝山脉之间存在现已覆盖的大规模断层系统，并限制了在蓝色山脉东部的剪切Zones上容纳的脱氧量的量。这项研究将对这些白垩纪岩石的古色性提供牢固的约束，并为现有的构造模型提供了测试，以及这些模型在Ochoco Rock，Hornbrook形成和其他白垩纪盆地之间的潜在相关性方面的预测。该项目将通过将出处和古磁性沉积岩的生态磁性分析结合到重建白垩纪后期古地理的典范中，直接解决脐带构造的长期辩论。蓝山地区的晚白垩统沉积岩石提供了一个理想的机会，可以使用独立和免费方法来测试蓝山和相关地层的古地理和构造亲和力提出的几个想法。此外，获得的大型古磁数据集将允许使用三种独立的方法进行评估和校正，以纠正含磁铁矿的碎屑沉积物中的古磁性倾斜度误差。最后，确定在这里提出的边缘盆地的良好受限的古地理学将更好地证明，从给定盆地的碎屑矿物的热量矿物学获得的升高和剥夺的证据可以与北美尸体内的特定位置相关，从而有潜在地促进了我们对北美山脉的理解的重要进步。