Shortening, extension, and drainage reorganization in the Andean fold-thrust belt and broken foreland basin of northern Patagonia, Argentina

南美洲的安第斯山脉是沿会聚板块构造边界造山的关键位置，在那里，一个上覆的大陆板块在一个俯冲的海洋板块之上变形。虽然安第斯山脉的造山通常与大陆地壳的区域碰撞和缩短有关，但最近的研究指出了伸展变形的重要例子。该研究项目将研究巴塔哥尼亚安第斯山脉北部地壳变形的长期历史，在那里，缩短和伸展之间的交替似乎影响了地形、侵蚀、河流排水系统和沉积盆地的形成。该项目将利用多种分析技术，包括沉积盆地分析、地质年代学和构造地质学，以确定阿根廷南部巴塔哥尼亚盆地的年龄、持续时间和沉积过程。该项目将有助于确定地壳内部和地表的过程，这些过程影响由缩短和伸展变形产生的沉积盆地的形成。这项研究将对了解海洋-大陆板块边界的基本地质过程和相关地质灾害产生影响，并以信息的形式提供社会效益，使风险评估和基础设施规划得以改进。此外，该项目将促进学术界和工业界科学家之间的国际科学合作，并为本科生和研究生提供国际研究和培训机会。该项目将解决关于安第斯山脉的一个新兴争论，即延伸在长期以来被认为是沿着广泛的俯冲边缘不间断的缩短、增厚和隆起过程中所起的作用。在挤压应力和拉张应力之间波动的造山系统可能控制着安第斯型汇聚系统的构造和地层演化，这是由于板块运动学（回退/后退vs前缘推进）和俯冲-板块动力学（板块变浅vs变陡）在更大范围内的变化所驱动的机械耦合的边缘范围变化。本项目将重点研究巴塔哥尼亚北部安第斯褶皱冲断带和破碎前陆地区的一个未被充分研究的区域，该区域不仅包含白垩-新生代缩短和前陆盆地演化的证据，还包含安第斯岩浆弧不规则进退过程中伸展盆地发育和水系重组的证据。研究小组将对阿根廷南部的一个东西向样带进行沉积/构造盆地分析和恢复，包括加强沉积和变形记录，确定盆地边界结构的年代，新的U-Pb年代地层和物源限制，以及修订沉降和岩浆历史。研究结果将整合多个盆地系统，以确定南安第斯山脉缩短、伸展和停滞阶段的盆地成因、不整合发育、沉积物路径和排水重组模式。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Andes Mountains of South America are a key location for mountain building along convergent plate tectonic boundaries where an overriding continental plate is deformed above a subducting oceanic plate. Although Andean mountain building is generally associated with regional collision and shortening of continental crust, recent studies point to important examples of extensional deformation. This research project will address the long-term history of crustal deformation in the northern Patagonian Andes, where alternations between shortening and extension appear to have influenced the generation of topography, erosion, river drainage systems, and sedimentary basins. The project will utilize a variety of analytical techniques, including sedimentary basin analysis, geochronology, and structural geology to determine the age, duration, and depositional processes within the Patagonian basin of southern Argentina. The project will help define processes within the Earth's crust and at the surface that influence the formation of sedimentary basins produced by both shortening and extensional deformation. The study will have implications for understanding the fundamental geologic processes and associated geohazards along ocean-continent plate boundaries, offering societal benefits in the form of information that will enable improved risk assessment and infrastructure planning. In addition, the project will initiate international scientific collaborations between academic and industry scientists and support international research and training opportunities for undergraduate and graduate students.The project will address an emerging debate for the Andes regarding the role of extension during what has been long regarded as uninterrupted shortening, thickening, and uplift along an extensive subduction margin. An orogenic system that fluctuates between compressional and extensional stresses may govern the structural and stratigraphic evolution of Andean-type convergent systems, due to both margin-wide changes in mechanical coupling driven by plate kinematics (rollback/retreating vs. advancing margin) and more-regional changes in subducting-slab dynamics (slab shallowing vs. steepening). This project will focus on an understudied segment of the Andean fold-thrust belt and broken foreland region of northern Patagonia, which contains evidence of not only Cretaceous-Cenozoic shortening and foreland basin evolution but also extensional basin development and drainage reorganization during irregular advance and retreat of the Andean magmatic arc. The research team will conduct a sedimentary/structural basin analysis and restoration of a regional east-west transect in southern Argentina, that will include an enhanced depositional and deformational record, dating of basin-bounding structures, new U-Pb chronostratigraphic and provenance constraints, and revised subsidence and magmatic histories. The results will enable integration across several basin systems in order to identify the patterns of basin genesis, unconformity development, sediment routing, and drainage reorganization during contrasting phases of shortening, extension, and stasis in the southern Andes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.