Collaborative Research: Utilizing Cooling Histories to Determine the Sequence and Rates of Thrusting

合作研究：利用冷却历史来确定推进的顺序和速率

• 批准号: 1524277
• 负责人: Nadine McQuarrie
• 金额: $ 27.81万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1524277&HistoricalAwards=false
• 关键词: Collaborative; Research; Utilizing; Cooling; Histories

This proposal is aimed at understanding the structural, tectonic, and exhumation of a part of the Himalayan orogen in central and western Nepal. The principal investigators are investigating how fault magnitude, geometry and rate are related to uplift and exhumation in convergent margin plate tectonic systems where two continents are colliding. This research will allow the principal investigators to constrain both magnitude and age of faulting and gain insight into the geometry of these faults along a fundamental plate boundary between India and Asia in the Nepalese Himalaya, which will provide fundamental insights into how convergent plate margins evolve through time. This region is the site of large, destructive earthquakes that are a function of both geometry of the faults and the rates at which these faults move; thus, the research has the potential to further understanding in a region of active seismicity. This proposal combines thermochronometry (the age at which minerals cool) with numerical modeling to determine fault magnitude, geometry and rate. Geologic mapping and associated cross sections provide an estimate of fault geometry. This geometry provides a testable path along which rocks were displaced and cooled from the subsurface to the Earth's surface. The principal investigators will test the hypothesis that the geometry of faults controls the first-order pattern of cooling ages that are recorded in rocks, which can then be tested by comparing measured cooling ages to modeled cooling ages using different fault geometries. This approach will provide workflows, methodologies, and examples of how fault geometries, as determined from geologic cross sections, and rates impact predicted cooling ages. In addition to the scientific objectives of the study, the project is contributing to the national well-being and other socially relevant outcomes by providing for training of graduate and undergraduate students in an important STEM discipline, as well a contributing to the broadening of underrepresented groups in the earth sciences. The project it is contributing to the development of research infrastructure at two U.S. university systems, and is promoting international collaboration between U.S., German, and Nepalese scientists. Results from this research will be incorporated into classroom curricula. As part of this project, the principal investigators are developing a series of research and teaching modules that will provide interested graduate students and researchers from other institutions the skills needed to use this research approach for their own field areas and datasets, and allow educators to assign advanced undergraduates and graduate students assignments that teach the systematics of how compressional fault systems form and the relationships between deformation, erosion and deposition. The results of the research will be disseminated through peer-reviewed scientific publications literature and by presentations at professional society meetings; data obtained from the project will be archived in appropriate community supported data repositories. Combining thermochronometry with numerical modeling has an enormous potential to quantify the rates, magnitudes, and timing of deformation and erosion in active, contractional plate tectonic settings. However, the interpretations of thermochronometric data are critically dependent on determining the correct thermal, kinematic, and erosion models. Understanding how fault magnitude, geometry and rate are related to exhumation in compressional systems requires quantitatively linking the geometry and magnitude of fault slip to the distribution and amount of erosion. In this project, the principal investigators suggest that the geometry of fold-thrust belts is best delineated through balanced geologic cross-sections, and they hypothesize that the geometry of a fold-thrust belt, particularly the location and magnitude of ramps in the decollement, control the first-order pattern of cooling ages. To address this hypothesis they will apply a 2 dimensional thermo-kinematic and erosion model to forward modeled balanced cross sections to quantify the cooling history in a thrust belt setting. Balanced cross-sections provide the kinematic sequence of rocks and structures necessary to reproduce the mapped surface geology. The principal investigators will test the validity of this kinematic sequence by assigning ages over which displacement occurs, and use the range of potential velocity vectors to calculate heat transport, erosion, and rock cooling. Matching the measured cooling histories recorded by a suite of thermochronometers to that predicted by the kinematics of a balanced cross-section is an additional support for the validation of the cross section. This work will examine proposed structural geometries, the cooling ages of rocks and their interdependence in central Nepal and far western Nepal. In central Nepal, there is an abundance of geochronologic/thermochronologic data and recent maps and cross section interpretations. In far western Nepal, there are detailed maps and cross section interpretations with a growing body of geochronologic/thermochronologic data. The researchers will capitalize on these established and growing datasets to test our hypothesis by 1) evaluating a range of permissible geometries for balanced-sections (both prior to and following field work), 2) collecting critical field observations (bedding, foliation, cleavage) and necessary thermochronologic samples, 3) establishing the cooling history of duplexes and thrust sheets via a suite of thermochronometers, and 4) modeling the dependence of chronometers on structural geometries, displacement paths and rates. The intellectual merit of this project involves investigating the sensitivity and utility of thermochronometer and kinematic data for calculating the age and rate of thrust motion and associated exhumation. Using this approach in Nepal, the principal investigators can evaluate the range of shortening rates in space and time and determine if long-term shortening rates though the Himalaya are constant or variable. These methods/processes will be transportable to other contractional systems worldwide and will lead to a reevaluation of the kinematics, geometry and rates in orogenic systems.

该提案旨在了解尼泊尔中西部部分喜马拉雅造山带的结构、构造和折返。主要研究人员正在研究断层大小、几何形状和速率与两个大陆碰撞的会聚边缘板块构造系统中的隆升和折返之间的关系。这项研究将使主要研究人员能够限制断层的规模和年龄，并深入了解沿着尼泊尔喜马拉雅山印度和亚洲之间的基本板块边界的这些断层的几何形状，这将为了解汇聚板块边缘如何演化提供基础见解。时间。 该地区是大型破坏性地震的发生地，地震的发生与断层的几何形状和断层移动的速度有关。因此，这项研究有可能进一步了解活跃地震活动区域。该提案将热测时法（矿物冷却的年龄）与数值模型相结合，以确定断层强度、几何形状和速率。地质测绘和相关横截面提供了断层几何形状的估计。 这种几何形状提供了一条可测试的路径，岩石沿着该路径从地下移动并冷却到地球表面。主要研究人员将测试断层几何形状控制岩石中记录的冷却年龄的一阶模式的假设，然后可以通过将测量的冷却年龄与使用不同断层几何形状建模的冷却年龄进行比较来测试这一假设。该方法将提供工作流程、方法和示例，说明从地质横截面确定的断层几何形状和速率如何影响预测的冷却年龄。 除了研究的科学目标外，该项目还通过为研究生和本科生提供重要 STEM 学科的培训，以及扩大代表性不足的群体，为国家福祉和其他社会相关成果做出贡献在地球科学领域。该项目正在为美国两所大学系统的研究基础设施的发展做出贡献，并促进美国、德国和尼泊尔科学家之间的国际合作。这项研究的结果将纳入课堂课程。作为该项目的一部分，主要研究人员正在开发一系列研究和教学模块，这些模块将为来自其他机构的感兴趣的研究生和研究人员提供在自己的领域和数据集上使用这种研究方法所需的技能，并允许教育工作者分配高级本科生和研究生作业，教授挤压断层系统如何形成以及变形、侵蚀和沉积之间关系的系统学。研究结果将通过同行评审的科学出版物文献和专业协会会议上的演讲进行传播；从该项目获得的数据将存档在适当的社区支持的数据存储库中。将热测时法与数值模拟相结合具有量化活跃收缩板块构造环境中变形和侵蚀的速率、幅度和时间的巨大潜力。然而，热测时数据的解释很大程度上取决于确定正确的热、运动学和侵蚀模型。要了解断层大小、几何形状和速率与挤压系统中折返的关系，需要将断层滑动的几何形状和大小与侵蚀的分布和数量定量联系起来。在这个项目中，主要研究人员建议，褶皱逆冲带的几何形状最好通过平衡的地质横截面来描述，他们假设褶皱逆冲带的几何形状，特别是滑脱带中坡道的位置和大小，控制冷却年龄的一级模式。为了解决这一假设，他们将应用二维热运动学和侵蚀模型来正向建模平衡横截面，以量化冲断带设置中的冷却历史。平衡的横截面提供了再现所绘制的表面地质所需的岩石和结构的运动序列。主要研究人员将通过指定位移发生的年龄来测试该运动序列的有效性，并使用潜在速度矢量的范围来计算热传输、侵蚀和岩石冷却。将一套测温仪记录的测量冷却历史与平衡横截面的运动学预测的冷却历史相匹配，是对横截面验证的额外支持。这项工作将研究尼泊尔中部和尼泊尔西部地区拟议的结构几何形状、岩石的冷却年龄及其相互依赖性。在尼泊尔中部，有大量的地质年代学/热年代学数据以及最新的地图和剖面解释。在尼泊尔西部地区，有详细的地图和剖面解释以及越来越多的地质年代学/热年代学数据。研究人员将利用这些已建立的和不断增长的数据集来检验我们的假设：1）评估平衡截面的一系列允许的几何形状（在现场工作之前和之后），2）收集关键的现场观察结果（层理、叶理、解理）和必要的热年代学样本，3）通过一套热计时仪建立双相体和推力片的冷却历史，4）模拟计时仪对结构几何形状、位移路径和费率。该项目的智力价值包括研究热计和运动学数据的灵敏度和实用性，以计算推力运动的年龄和速率以及相关的折返。在尼泊尔使用这种方法，主要研究人员可以评估空间和时间缩短率的范围，并确定喜马拉雅山的长期缩短率是恒定的还是可变的。这些方法/过程将可移植到世界各地的其他收缩系统，并将导致对造山系统的运动学、几何形状和速率的重新评估。