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，可能导致新的海洋盆地的形成。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，沿着新墨西哥州的格兰德河和加州湾。裂谷地区往往集中自然资源（例如，碳氢化合物，金属，地热），并可能与重大的地震灾害。因此，理解形成裂谷结构和景观的过程在基础和社会层面上都是至关重要的。该项目专门研究两个关键裂谷过程的敏感性：断层生长和岩浆活动对地形应力的敏感性，地形应力是地壳中由于地形起伏而产生的力。已知这种应力会影响构造板块碰撞的大陆变形（例如，台湾，喜马拉雅山），但很少有人知道他们对大陆裂谷的影响。这些应力受到河流和冰川的侵蚀作用以及盆地和低地沉积物的重量的强烈调制。这项研究将结合联合收割机的数值模型和实地观察，以评估这种活跃的表面过程如何影响断层的发展和裂谷期间火山活动的空间范围。它将支持一个早期的职业科学家以及少数民族研究生。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解决了在整个造山带（100？1000公里）。然而，很少的工作已经做了伸展环境中，岩浆过程是板块边界演化的一个组成部分，和相当大的地形增长的规模，个别正常的断层边界范围（10？100公里）。本研究的目的是耦合现有的裂谷模型与现实的景观演化参数化，以揭示地形增长和构造岩浆变形之间的反馈在深度。具体而言，该项目将首先使用景观演化模型记录全球裂谷中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，正断层下盘的总起伏、主要汇水盆地的形态和上盘块体的沉积充填。然后，我们将实现这些校准的景观模型作为一个长期的构造模型，断层可以自发形成和岩浆侵入体响应环境应力场的上边界条件。大量的数值模拟将使以下假设得以检验：（1）下盘的剥蚀和上盘的沉积是使半地堑能够容纳与断层上地壳厚度相当的错距的必要条件;（2）地垒的形成是由低效的地表过程促进的，它保持了断层附近的地形起伏并有利于地形应力的积累;（3）表层岩体的有效再分布使岩浆活动集中于裂谷轴部。将把模型输出与断层增长和火山就位的实地观测进行系统比较，以确定地表过程对大陆裂谷的构造-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.