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由两个构造板块的汇聚和碰撞造成的，其中纳斯卡板块在称为俯冲的过程中以浅角度推向南美洲板块下方。该项目将解决平板俯冲对大陆变形的影响，大陆变形导致南美洲西缘安第斯山脉急剧隆起。 PI旨在更好地理解导致阿根廷安第斯山脉生长的地质和地球动力学过程，其结果将对理解古代造山过程产生重要影响，例如在塞维尔和拉拉米德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技术研究委员会 (CONICET) 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各个方面。该项目将通过让学生参与高影响力的研究项目和参与跨文化的国际经验，促进本科生的培训；它还将有助于扩大代表性不足的群体对 STEM 的参与。研究结果将纳入研究课程，并通过会议和出版物的演示形式广泛传播。该项目还有可能提高对经历过多次毁灭性历史地震的研究地区地震风险的了解。关于沿着会聚板块边缘的大陆变形的基本控制仍然存在第一级问题，包括薄皮上地壳到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。该项目将整合各种结构和岩石磁技术，以便更好地了解纳扎板块的平板俯冲及其与压倒性南美板块的相互作用所导致的变形的空间和时间变化。该项目将涉及断层、褶皱和裂缝系统的测量和分析；测量磁化率各向异性以表征变形织物；将利用古地磁分析来了解地壳块如何因变形而旋转；并将利用地球物理数据构建地质剖面。这项工作将重点关注五个横断面，这些横断面跨越了正常俯冲到平板俯冲的影响，并穿过阿根廷西北部的厚皮山脉潘皮纳斯带、薄皮Precordillera带和混合模式主科迪勒拉带。该项目将： 量化复杂山地系统（厚皮前陆、薄皮褶皱逆冲带、混合模式带）的垂直轴旋转和应力/应变场的时空变化；为该区域的 3 维运动学演化提供新模型；测试地球动力学模型，预测与从正常俯冲到平板俯冲过渡相关的结构样式、应力模式、旋转和板内缩短率的不同沿走向变化；评估地壳流变、基底弱点和盆地反转对构造趋势、应力折射和变形划分模式的影响；并统计比较根据断层数据、磁性结构分析、地震震源机制和可用的全球定位卫星数据估计的应力/应变方向。支持与该项目相关的国际活动的资金由美国国家科学基金会国际科学与工程办公室提供。

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.