Hypsometric History of the North American Continental Interior and Implications for Mantle Dynamics

北美大陆内部的高度历史及其对地幔动力学的影响

• 批准号: 1450181
• 负责人: Rebecca Flowers
• 金额: $ 29.68万
• 依托单位: University of Colorado at Boulder
• 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: 2015-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1450181&HistoricalAwards=false
• 关键词: Hypsometric; History; North; American; Continental

The project represents an interdisciplinary study aimed at understanding the thickness, spatial extent, and evolution of long-eroded sections of the Phanerozoic stratigraphic record across the continental interior in order to understand cryptic variations in paleoelevation of the Earth's surface and how variations in the properties of the mantle have influenced its history. It has long been recognized that cryptic elevation changes in the continental interior have occurred through the geologist past, but such changes are difficult to reconcile by conventional plate tectonic models in which deformation is largely related to processes at or near plate margins. The principal investigators posit that variations in vertical motion of the Earth's crust, termed dynamic topography, are related to the interaction of the Earth's lithosphere with convection deep within the mantle. The project will involve a combination of thermochronology, geologic age constraints, and 3D modeling to test hypotheses related to how mantle dynamics of the Earth's mantle affects surface processes. The project represents a fundamental contribution to furthering understanding of how deformation of the Earth's crust may be linked with processes deep within the planets interior. In addition scientific goals of the research, the project is contributing to research infrastructure; is supporting the research efforts of a faculty member who is a member of an underrepresented group in the geosciences; is contributing to the training of a Ph.D. student in a STEM (Science, Technology, Engineering, and Mathemathics) discipline; is supporting the involvement of an undergraduate student intern from the University of Colorado's Research Experiences in Solid Earth Science for Students (RESESS), which is a program that promotes diversity within the Earth Sciences; and is providing for international collaboration between U.S. and Australian scientists. Cryptic epeirogenic elevation change in continental interiors is not easily accounted for by plate margin tectonism, suggesting that fundamental aspects of geodynamics and continental evolution are not yet understood. Nevertheless, this problem has received comparatively little attention in geologic investigations. Dynamic topography, produced by vertical motion of the Earth's surface in response to normal traction generated by mantle convection, provides an attractive explanation for aspects of the North American interior surface history that otherwise are not easily explained by tectonic processes. However, despite the increasing sophistication and diversity of dynamic modeling efforts, it remains challenging to definitively test these models. There is now enormous demand for geologic constraints to better calibrate dynamic models and discriminate between their different predictions. The multistep approach to be employed in this study is characterized by 1) thermochronology data acquisition at a scale appropriate to deduce regional trends, 2) reconstruction of the regional burial, unroofing and elevation change history by coupling of thermochronologic and geologic constraints, 3) comparison of this surface history with the vertical motion predictions of a 3D dynamic model of thermochemical convection, and 4) experimentation with reasonable modifications to the dynamic model to evaluate the sensitivity of the fit to different parameters. This study is framed around two key hypotheses concerning mantle dynamic controls on the surface evolution of the North American interior that emerged from previous work. The proposed will expand these past efforts spatially across a broader region of the continent as well as temporally into the Cretaceous. Hypothesis 1: Mantle flow associated with supercontinent evolution was an important control on the Paleozoic-early Mesozoic hypsometric history of the North American interior. Hypothesis 2: Cretaceous burial was more substantial across the entire central U.S. than recognized previously, which is key for accurately calibrating dynamic models of Farallon slab evolution.

该项目是一项跨学科研究，旨在了解整个大陆内部古生代地层记录的长期侵蚀部分的厚度、空间范围和演变，以了解地球表面古高程的神秘变化以及地幔性质的变化如何影响其历史。长期以来，人们一直认为大陆内部的神秘海拔变化发生在地质学家的过去，但这种变化很难用传统的板块构造模型来调和，在传统的板块构造模型中，变形主要与板块边缘或附近的过程有关。主要研究人员认为，地壳垂直运动的变化，称为动态地形，与地球岩石圈与地幔深处对流的相互作用有关。该项目将涉及热年代学，地质年龄限制和3D建模的组合，以测试有关地球地幔的地幔动力学如何影响表面过程的假设。该项目为进一步了解地壳变形如何与行星内部深处的过程联系起来做出了根本性贡献。除了研究的科学目标外，该项目还为研究基础设施做出贡献;支持一名教师的研究工作，该教师是地球科学中代表性不足的群体的成员;为培养博士生做出贡献。该项目为STEM（科学、技术、工程和数学）学科的一名学生提供支持;支持科罗拉多大学学生固体地球科学研究经验项目（RESESS）的一名本科生实习生的参与，该项目旨在促进地球科学的多样性;并为美国和澳大利亚科学家之间的国际合作提供支持。 在大陆内部的神秘造陆高程变化是不容易占板块边缘构造，这表明地球动力学和大陆演化的基本方面还没有被理解。然而，这个问题在地质调查中受到的关注相对较少。动态地形，地球表面的垂直运动产生的地幔对流产生的正常牵引，提供了一个有吸引力的解释方面的北美内部表面的历史，否则不容易解释的构造过程。然而，尽管动态建模工作的复杂性和多样性不断增加，但对这些模型进行最终测试仍然具有挑战性。现在有巨大的需求地质约束，以更好地校准动态模型和区分他们的不同预测。本研究采用的多步骤方法的特点是：1）在适当的尺度上获取热年代学数据，以推断区域趋势，2）通过耦合热年代学和地质约束，重建区域埋藏、去顶和高程变化历史，3）将该地表历史与热化学对流的三维动态模型的垂直运动预测进行比较，以及4）对动态模型进行合理修改的实验，以评估拟合对不同参数的灵敏度。这项研究是围绕两个关键的假设，从以前的工作中出现的北美内陆的表面演变地幔动力学控制。该计划将在空间上将这些过去的努力扩展到更广泛的大陆区域，并在时间上扩展到白垩纪。假设1：与超大陆演化相联系的地幔流动对北美大陆内部古生代-早中生代的地壳厚度变化历史具有重要的控制作用。假设二：白垩纪的埋藏在整个美国中部比以前认识到的要多，这是准确校准法拉隆板块演化动力学模型的关键。