Collaborative Research: Interrelations Between Foreland Deformation and Flat-slab Subduction: Integrated Analysis of the Sierras Pampeanas to Cordillera of the South-central Andes

南美洲西部的现代地形是两个构造板块会聚和碰撞的结果，其中纳斯卡板块在一个称为俯冲的过程中以浅角度被推入南美洲板块之下。该项目将探讨板块俯冲在产生大陆变形方面的影响，这种变形导致沿着南美洲西部边缘的安第斯山脉急剧隆起。PI旨在更好地了解导致阿根廷安第斯山脉增长的地质和地球动力学过程，其结果将对了解古代造山过程产生重要影响，例如在Sevier和Laramide造山运动期间形成美国西部落基山脉的构造过程。该项目涉及与阿根廷国家科学和技术研究理事会的阿根廷地球科学家及其学生进行重要的科学合作，他们将参与该项目的所有方面。该项目将通过学生参与高影响力的研究项目和参与跨文化的国际经验，为本科生的培训做出贡献;它还将有助于扩大STEM中代表性不足的群体的参与。研究结果将纳入研究课程，并将通过会议介绍和出版物广泛传播。该项目也有可能提高对研究区域地震风险的理解，该研究区域经历了多次毁灭性的历史地震。关于大陆变形沿着会聚板块边缘的基本控制，一级问题仍然存在，包括薄皮上地壳与厚皮下地壳变形的原因和相互作用，预先存在的地壳弱点的影响，以及与俯冲动力学的关系。该项目将综合各种结构和岩石磁性技术，以便更好地了解纳扎板块的平板俯冲及其与上覆的南美板块的相互作用所造成的变形的时空变化。该项目将涉及测量和分析断层、褶皱和断裂系统;测量磁化率各向异性以确定变形组构的特征;将利用古地磁分析了解地壳块体如何因变形而旋转;并将利用地球物理数据绘制地质剖面。这项工作将集中在五个断面，跨越正常的平板俯冲的影响，并穿越厚皮Sierras Pampeanas，薄皮Precordillera，和混合模式的主科迪勒拉带阿根廷西北部。该项目将：量化复杂山地系统中应力/应变场的垂直轴旋转和时空变化（厚皮前陆、薄皮褶皱冲断带、混合模式带），为该区三维运动学演化提供了新的模式;测试地球动力学模型，预测不同的结构样式，应力模式，旋转，和板内缩短率有关的过渡从正常到平板俯冲，评估地壳流变学的影响，基底的弱点，盆地反转模式的结构趋势，应力折射，变形分区;并统计比较从断层数据，磁组构分析，地震震源机制，和可用的全球定位卫星数据。基金，以支持与这一项目有关的国际活动正在提供的NSF办公室，国际科学与工程.

The modern-day topography of western South America results from the convergence and collision of two tectonic plates wherein the Nazca Plate is being shoved at a shallow angle beneath the South American plate in a process called subduction. This project will address the effects of flat-slab subduction in producing the continental deformation that has resulted in the dramatic uplift of the Andes along the western margin of South America. The PIs seek to provide better understanding of the geologic and geodynamic processes that have resulted in the growth of the Argentine Andes, and their results will have important implications for the understanding of ancient mountain building processes, such as the tectonic processes that formed the Rocky Mountains of the western United States during the Sevier and Laramide orogenies. The project involves a significant scientific collaboration with Argentinian geoscientists from the Argentina National Council of Scientific and Technical Research (CONICET) and their students, who will be involved in all facets of the project. The project will contribute to the training of undergraduate students through involvement of students in high-impact research projects and participation in cross-cultural international experiences; it will also contribute to the broadening of participation of underrepresented groups in STEM. Results of the research will be incorporated into research curricula and will be widely disseminated through presentations at meetings and publications. The project also has the potential to improve understanding of seismic risks in the study region that has experienced multiple devastating historic earthquakes. First-order questions persist regarding fundamental controls of continental deformation along convergent plate margins, including causes and interactions of thin-skin upper crustal to thick-skin lower crustal deformation, influences of pre-existing crustal weaknesses, and relations to subduction dynamics. This project will integrate a variety of structural and rock magnetic techniques in order to better understand the spatial and temporal changes in deformation that have resulted from flat slab subduction of the Naza plate and its interaction with the overriding South American plate. The project will involve the measurement and analysis of faults, folds, and fracture systems; measurements of the anisotropy of magnetic susceptibility to characterize deformation fabrics; will utilize paleomagnetic analysis to understand how crustal blocks have rotated due to deformation; and will use construction of geological cross-sections utilizing geophysical data. The work will focus on five transects that span the effects of normal to flat-slab subduction, and which cross the thick-skin Sierras Pampeanas, thin-skin Precordillera, and mixed mode Principal Cordillera belts of northwest Argentina. The project will: quantify both vertical-axis rotations and spatial-temporal changes in stress/strain fields across a complex mountain system (thick-skin foreland, thin-skin fold-thrust belt, mixed mode belt); provide a new model for the 3-dimensional kinematic evolution of the region; test geodynamic models that predict different along-strike variations in structural style, stress patterns, rotations, and intraplate shortening rates related to a transition from normal to flat-slab subduction; evaluate effects of crustal rheology, basement weaknesses, and basin inversion on patterns of structural trend, stress refraction, and deformation partitioning; and statistically compare stress/strain directions estimated from fault data, magnetic fabric analysis, earthquake focal mechanisms, and available global positioning satellite data.Funds to support the international activities associated with this project are being provided by the NSF Office of International Science and Engineering.