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.

该项目代表了一项跨学科研究，旨在理解整个大陆内部幻生地层记录的长期修饰部分的厚度，空间范围和演变，以了解地球表面的神秘性差异以及架子的特性中的变化如何影响其历史。长期以来，人们已经认识到，大陆内部的神秘高度变化是通过地质学家的过去发生的，但是这种变化很难通过常规的板块构造模型来调和，其中变形与板缘或附近的过程很大程度上相关。主要研究人员认为，地壳的垂直运动的变化称为动态地形，与地球岩石圈与地幔深处的对流的相互作用有关。该项目将涉及热量学，地质年龄限制和3D建模的结合，以测试与地球地幔的地幔动力学如何影响表面过程有关的假设。该项目代表了进一步了解地壳变形如何与行星内部深处的过程联系在一起的基本贡献。此外，研究的科学目标，该项目为研究基础设施做出了贡献。正在支持地球科学中代表性不足的教职员工的研究工作；有助于培训博士学位。 Stem（科学，技术，工程和数学）学科的学生；正在支持科罗拉多大学固体地球科学研究经验（Resess）的本科生实习生的参与，该计划是一项促进地球科学中多样性的计划；并提供了美国和澳大利亚科学家之间的国际合作。 板缘构造不容易解释大陆室内室内的隐性自我生成升高变化，这表明尚未了解地球动力学和大陆进化的基本方面。然而，这个问题在地质研究中受到了相对较少的关注。由地球表面的垂直运动产生的动态形态是响应于地幔对流产生的正常牵引力的，为北美内部表面历史的各个方面提供了一个有吸引力的解释，否则否则就无法轻易通过构造过程来解释。但是，尽管动态建模工作的复杂性和多样性越来越多，但确定测试这些模型仍然具有挑战性。现在，人们对地质限制有很大的需求，以更好地校准动态模型并区分其不同的预测。本研究中要采用的多步态方法的特征是1）在适当推论区域趋势的规模上采集数据的特征，2）重建区域埋葬，不盖和高程变化历史的历史，通过热力学和地质学约束的耦合，将表面历史与垂直运动的垂直动态模型比较，3）修改动态模型以评估拟合对不同参数的灵敏度。这项研究围绕着关于北美内部表面演变的地幔动态控制的两个关键假设，这些假设是从先前的工作中出现的。拟议的将在整个大陆的更广阔地区以及时间上扩展到过去的这些努力。假设1：与超大陆进化相关的地幔流是对北美内部古生代 - 美味的中生代催眠病史的重要控制。假设2：在整个美国中部，白垩纪埋葬比以前所认识的要实质性更高，这对于准确校准Farallon平板演化的动态模型是关键。