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

裂谷是大陆被拉伸并最终分裂的过程，可能导致形成一个新的海洋盆地。活跃的裂谷作用目前正在北美的大部分地区进行，例如在盆地和山脉省，沿着新墨西哥州的里约热内卢格兰德河，以及在加利福尼亚湾。裂谷区通常集中自然资源（例如碳氢化合物、金属、地热），并可能与重大地震危险有关。因此，了解形成裂缝建筑和景观的过程在基础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裂陷过程的敏感性：断层生长和岩浆活动对地形应力的影响，地形应力是由于地形起伏的积累而在地壳中产生的力。这种应力已知会影响构造板块碰撞的大陆变形（如台湾、喜马拉雅山），但对它们对大陆裂谷的影响知之甚少。这些应力受到河流和冰川的侵蚀作用以及在盆地和低地积聚的沉积物的重量的强烈调节。本研究将结合数值模型和实地观测来评估这种活跃的地表过程如何影响断裂发育和裂谷期间火山活动的空间范围。它将支持一名早期职业科学家和一名少数民族研究生。这项研究的成果将作为科学推广活动的一部分广泛分发，并为教育工作者和荒野保护区提供材料。许多实地和理论研究已经在整个造山带的尺度上解决了表面过程和应变局部化之间的反馈(100？1000公里)。然而，在伸展环境中所做的工作很少，在伸展环境中，岩浆作用是板块边界演化的一个组成部分，并且在单个正断层边界范围(10？100公里)。本研究的目的是将现有的裂谷模型与景观演化的现实参数化相结合，以揭示地形生长与深部构造-岩浆变形之间的反馈。具体而言，该项目将首先使用景观演化模型记录全球裂谷的质量再分配效率的全部范围，该模型允许与可观测数据进行直接比较，例如，正常断层下盘的总起伏、主要汇水盆地的形态以及上盘块的沉积充填。然后，我们将这些校准的景观模型作为一个长期构造模型的上边界条件，在这个模型中，断层可以自发形成，岩浆侵入对环境应力场做出反应。大量的数值模拟将验证以下假设：(1)下盘的剥蚀和上盘的沉积对于允许半地堑容纳与断裂的上地壳厚度相称的偏移是必不可少的；(2)低效率的地表作用促进了地垒的形成，从而保持了地形起伏，有利于断层附近地形应力的积累；(3)地表物质的有效再分配将岩浆活动集中在裂谷轴上。将系统地将模型输出与断层生长和火山侵位的实地观测进行比较，以确定地表过程对大陆裂谷构造-岩浆演化的贡献。

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.