Collaborative Research: Quantifying the Sensitivity of Rifting Processes to Erosion and Sedimentation

合作研究：量化裂谷过程对侵蚀和沉积的敏感性

• 批准号: 1650244
• 负责人: Mark Behn
• 金额: $ 21.85万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-02-01 至 2018-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1650244&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantifying; Sensitivity; Rifting

Rifting is the process by which continents get stretched and ultimately break apart, potentially leading to the formation of a new ocean basin. Active rifting is currently underway throughout large extents of North America, for example within the Basin and Range Province, along the Rio Grande River in New Mexico, and in the Gulf of California. Rifting areas often focus natural resources (e.g., hydrocarbons, metals, geothermal heat) and can be associated with significant seismic hazards. Understanding the processes that shape rift architecture and landscapes is therefore essential on both a fundamental and societal level. This project specifically investigates the sensitivity of two key rifting processes: fault growth and magmatic activity to topographic stresses, which are forces in Earth's crust due to the build-up of topographic relief. Such stresses are known to affect continental deformation where tectonic plates collide (e.g., Taiwan, the Himalayas), but little is known regarding their influence on continental rifting. These stresses are strongly modulated by the erosive action or rivers and glaciers, and the weight of sediments accumulating in basins and lowlands. This study will combine numerical models and field observations to assess how such active surface processes influence fault development and the spatial extent of volcanic activity during rifting. It will support an early-career scientist as well as a minority graduate student. The products of this study will be widely distributed as part of scientific outreach initiatives, and provide material for educators and wilderness conservation areas.Numerous field and theoretical studies have addressed the feedbacks between surface processes and strain localization in convergent margins at the scale of entire orogens (100?1000 km). However, very little work has been done in extensional settings, where magmatic processes are an integral part of plate boundary evolution, and sizeable topography grows at the scale of individual normal fault-bounded ranges (10?100 km). The goal of this study is to couple existing rifting models with a realistic parameterization of landscape evolution in order to uncover feedbacks between topography growth and tectono-magmatic deformation at depth. Specifically, the project will first document the full range of mass redistribution efficiency in rifts worldwide using a landscape evolution model that allows direct comparison with observables, e.g., the total relief of normal fault footwalls, the morphology of their major catchment basins, and the sedimentary infill of the hanging wall block. We will then implement these calibrated landscape models as an upper boundary condition in a long-term tectonic model where faults can form spontaneously and magmatic intrusions respond to the ambient stress field. A large suite of numerical simulations will enable tests of the following hypotheses: (1) Denudation of the footwall and deposition on the hanging wall are essential in allowing half-grabens to accommodate offsets commensurate with the thickness of the faulted upper crust; (2) Horst formation is promoted by inefficient surface processes, which preserve relief and favor the build up of topographic stresses near the fault; and (3) Efficient redistribution of surficial masses focuses magmatic activity to the rift axis. Model outputs will be systematically compared with field observations of fault growth and volcanic emplacement to identify the contribution of surface processes to the tectono-magmatic evolution of continental rifts.

裂谷是大陆被延伸并最终破裂的过程，可能导致形成新的海洋盆地。目前正在整个北美大型范围内的活动裂谷正在进行中，例如在盆地和山脉省内，新墨西哥州的里奥格兰德河沿线以及加利福尼亚海湾。裂谷区域通常集中于自然资源（例如碳氢化合物，金属，地热热），并且可能与重大的地震危害有关。因此，了解塑造裂谷建筑和景观的过程在基本和社会层面上都是必不可少的。该项目专门研究了两个关键的裂缝过程的敏感性：断层生长和岩浆活动对地形应力，它们是地壳中的力量，这是由于地形浮雕的积累。已知这种应力会影响大陆变形，而构造板碰撞（例如台湾，喜马拉雅山脉），但关于它们对大陆裂纹的影响鲜为人知。这些应力是通过侵蚀作用，河流和冰川的强烈调节，以及在盆地和低地积累的沉积物的重量。这项研究将结合数值模型和现场观测，以评估这种主动表面过程如何影响断层发育和裂谷过程中火山活动的空间范围。它将支持早期职业科学家以及少数研究生。这项研究的产品将作为科学外展计划的一部分进行广泛分布，并为教育工作者和荒野保护区提供材料。杂货领域和理论研究已经解决了整个Orogens（100？1000公里）的表面过程和融合边缘的应变定位之间的反馈。但是，在扩展设置中，很少完成工作，在岩浆过程中，岩浆过程是板边界进化的组成部分，并且在单个正常断层构造的范围（10？100 km）的规模上增长了相当大的地形。这项研究的目的是将现有的裂谷模型与景观演化进行现实的参数化，以发现地形增长与深度构造魔术变形之间的反馈。具体而言，该项目将首先使用景观演化模型来记录全球裂谷中的全部质量再分配效率，该模型允许直接比较可观察到的，例如，正常故障脚壁的总浮雕，其主要集水盆地的形态，其主要集水区的形态以及悬挂墙块的沉积物。然后，我们将在长期的构造模型中实施这些校准的景观模型作为上边界条件，在长期构造模型中，断层可以自发形成，而岩浆入侵响应环境应力场。一大堆数值模拟将实现以下假设的测试：（1）对脚壁的剥离和悬挂壁上的沉积对于允许半grabens适应与断层上皮的厚度相称的偏移； （2）HORST的形成是通过效率低下的表面过程来促进的，该过程可以保留浮雕并有利于在断层附近的地形应力增加； （3）有效的表面质量重新分布将岩浆活性聚焦于裂谷轴。模型输出将与故障生长和火山层面的现场观察系统进行系统的比较，以确定地表过程对大陆裂谷的构造量化演变的贡献。