Collaborative Research: Linking sediment dispersal, stratal architecture, and tectonic subsidence mechanisms in the Late Cretaceous Cordilleran Foreland Basin

这一多学科合作项目评估了科迪勒前陆岩石圈的下沉和沉积物沉积对北美西部边缘之下的大洋构造板块俯冲造成的白垩纪下沉的响应作用。这项研究有可能通过结合沉积分析和盆地分析、热年代学和地球动力学模拟来澄清平坦俯冲对上地壳和盆地的影响，从而改变对岩石圈规模过程的理解，从而能够区分地壳加载机制的相对贡献。除了该项目的科学目标外，合作还促进了STEM(科学、技术、工程和数学)教育工作者的发展，扩大了未被充分代表的群体对科学的参与，培训了一名博士后研究员以及研究生和本科生，从而推动了重要的社会成果。阿拉斯加大学的公众宣传努力，以及通过休斯顿大学与当地中学和中学年龄在家上学的学生之间新建立的关系对中学生的教育，有助于提高公众的科学素养和公众对STEM的参与。该项目还支持参与的大学和行业之间建立新的合作伙伴关系，从而有助于提高美国的经济竞争力。尽管长期以来，迁移动力下沉一直被用来解释晚白垩世沉积中心的扩大和迁移，但还没有研究采取高分辨率的大规模方法来表征迁移的时间或方向，或者区分弯曲下沉和动态下沉。然而，挠曲载荷和地壳下载荷留下了不同的前陆盆地沉积，记录了沉积物源区和物源区的折返速率，并具有记录下沉轨迹和速率的特征充填几何。对地层结构、沉积物体积、沉积物来源和沉积产品的详细调查使研究小组能够探索大洋高原平坦俯冲与持续或增强的冲断带折返或早期的基底岩心隆起之间的潜在影响。科迪勒系统提供了一个无与伦比的机会，可以在地球上最古老的弧后前陆盆地系统中确定大洋高原的平坦俯冲效应；因此，这项研究的结果适用于其他大洋-大陆会聚系统。研究小组正在通过整合砂岩成分数据、碎屑温度和地质年代学、高分辨率层序地层学、高分辨率等厚图、地史分析以及正演地层学、挠曲和地球动力学模型来评估观察到的盆地结构变化的机制。新的碎屑年代学和砂岩成分数据是对已发表的年代学和沉积学的补充，以更准确地确定这段时间内沉积物来源和路线的变化。碎屑热年代学描绘了滞后时间的向上剖面变化，与物源折返速率的变化相对应，或引入了新的沉淀物来源。层序地层学、解压等厚图和正演地层学模型允许计算和比较平均泥沙供应，以区分泥沙供应引起的盆地结构变化和可容纳驱动的变化。正在使用详细的等厚图和地史分析重建盆地沉降，这有助于区分地壳载荷和次地壳载荷。最后，弯曲模型和地球动力学模型能够区分加载机制的相对贡献。该项目将首次将碎屑地质和热年代学双重测年、高分辨率层序地层学和能够区分下沉机制的尺度和分辨率的多重建模工作的优势结合起来。作为这种合作的结果，该项目有可能通过澄清平面俯冲对上地壳和盆地的影响来改变对岩石圈尺度过程的理解。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。

This multidisciplinary collaborative project evaluates the role of subsidence of the lithosphere and deposition of sediments in Cordilleran foreland in response to Cretaceous subsidence caused by subduction of an oceanic tectonic plate beneath the western margin of North America. The research has the potential to transform understanding of lithosphere-scale processes by clarifying the effect of flat subduction on the upper crust and basins using a combination of sedimentary and basin analyses, thermochronology and geodynamic modelling to enable discrimination of the relative contributions of crustal loading mechanisms. In addition to the scientific goals of the project, the collaboration is advancing important societal outcomes by contributing to STEM (science, technology, engineering and mathematics) educator development, the broadening of participation of underrepresented groups in science, the training of a postdoctoral researcher and graduate and undergraduate students. Public outreach efforts by the University of Alaska and education of middle school students through newly established relationships between the University of Houston and local middle schools and middle-school aged homeschooled students contributes to increased public scientific literacy and public engagement with STEM. The project also supports the development of a new partnership between the participating universities and industry, thereby contributing to the increased economic competitiveness of the United States.Although migrating dynamic subsidence has long been invoked to explain the broadening and migration of the Late Cretaceous depocenter, no research has taken a high resolution, large-scale approach to characterizing the timing or direction of migration or to discriminate flexural from dynamic subsidence. However, flexural loading and subcrustal loading leave distinct foreland-basin deposits that record sediment source area and source area exhumation rate and have a characteristic fill geometry that records the locus and rate of subsidence. Detailed investigation of stratigraphic architecture, sediment volumes, sediment sources, and depositional products allows the research team to explore the potential influence of flat subduction of an oceanic plateau versus continued or enhanced thrust belt exhumation or incipient basement-cored uplifts. The Cordilleran system presents an unparalleled opportunity to establish the effect of flat subduction of an oceanic plateau in the best dated retroarc foreland basin system on the planet; thus, the results of this investigation are applicable to other ocean-continent convergent systems. The research team is evaluating mechanisms for observed changes in basin architecture by integrating sandstone compositional data, detrital thermo- and geochronology, high-resolution sequence stratigraphy, high-resolution isopach maps, geohistory analysis, and forward stratigraphic, flexural, and geodynamic modelling. New detrital geochronology and sandstone compositional data are supplementing published geochronology and sedimentology to more accurately identify changes in sediment provenance and routing during this time. Detrital thermochronology is delineating up-section changes in lag time, corresponding to changes in source exhumation rates, or introduction of a new sediment source. Sequence stratigraphy, decompacted isopach maps, and forward stratigraphic modelling allow calculation and comparison of the average sediment supply to discriminate changes in basin architecture due to sediment supply from accommodation-driven changes. Reconstruction of basin subsidence is being accomplished using detailed isopach maps and geohistory analysis, which facilitates discrimination of crustal loads from a subcrustal load. Finally, flexural and geodynamic modelling enables discrimination of the relative contributions of loading mechanisms. This project will combine, for the first time, the strengths of detrital geo- and thermochronological double-dating, high-resolution sequence stratigraphy, and multiple modeling efforts at a scale and resolution capable of discriminating the mechanisms for subsidence. As a result of this collaboration, this project has potential to transform the understanding of lithosphere-scale processes by clarifying the effect of flat subduction on the upper crust and basins.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.