Collaborative Research: Internal and external drivers of orogenic episodicity in the Ecuadorian Andes

厄瓜多尔拥有安第斯山脉形成期间与俯冲有关的岩浆活动和构造环境的重要记录。 这项研究将探讨构造旋回和洋壳增生在控制岩浆活动、地壳增厚和沿着洋-陆俯冲边缘盆地沉降等事件中的作用。 该项目将把穿越几个沉积盆地的区域研究结果与厄瓜多尔（安第斯山脉的最西端）的岩浆活动记录结合起来。 将采用一系列分析技术来确定盆地发展、沉积物来源和过去的水系发生重大变化的时间，并识别地壳增厚的时期、岩浆活动来源的变化以及增生洋壳的影响。 这项研究将深入了解沿着大洋-大陆俯冲板块边界的地质过程和地质灾害，提供信息，通过改进风险评估和基础设施规划造福社会。 该项目还将在国际学习经验的框架内促进新的学术合作，这将促进美国和厄瓜多尔研究人员之间的长期合作，包括开发共享的本科生和研究生地球科学实地考察课程和实地考察机会。在过去的十年中，竞争的观点已经出现在科迪勒西亚海洋-大陆板块边界的构造演化，包括安第斯山脉的地质历史，安第斯山脉是全球安第斯山脉会聚系统的原型。 争论主要源于对科迪勒拉体系的不同区域（弧前与弧后）和不同组成部分（盆地与岩浆弧与褶皱冲断带）的对比强调。 该项目将结合分析技术，如沉积盆地分析、同位素地球化学、岩石学和U-Pb地质年代学，以确定可能与内部驱动造山过程有关的盆地演化和弧岩浆活动的潜在耦合幕式阶段（包括俯冲、高通量岩浆作用和地壳/岩石圈根的堆积和沉降），或外部驱动的构造过程，包括波动的板块动力学（俯冲变浅与变陡的周期以及相关的快速与减少的缩短和沉降）和海洋沉积物增生。 厄瓜多尔包含了一个重要但未被充分认识的构造静止或可能的伸展记录，长期以来一直被认为是不间断的新生代缩短，增厚和沿着整个安第斯山脉边缘的隆起。 这种起伏的造山运动模式可能决定着许多大洋-大陆会聚边缘的结构和地层演化，并对俯冲和碰撞系统的构造机制产生影响。该奖项反映了NSF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。

Ecuador contains an important record of subduction-related magmatism and tectonic environments during the building of the Andes Mountains. This research will address the roles of tectonic cycles and the accretion of oceanic crust in regulating episodes of magmatism, crustal thickening, and basin subsidence along ocean-continent subduction margins. The project will integrate results from a regional traverse across several sedimentary basins with the record of magmatism across Ecuador, the narrowest segment of the Andes. A range of analytical techniques will be employed to determine the timing of major shifts in basin development, sediment sources, and past drainages, and to recognize periods of crustal thickening, changes in sources of magmatism, and the influence of accreted oceanic crust. The study will provide insights into the geologic processes and geohazards along ocean-continent subduction plate boundaries, offering information that will benefit society by improving risk assessment and infrastructure planning. The project will also catalyze new academic collaborations within the framework of international learning experiences that will facilitate longer term collaborations between US and Ecuadorian researchers, including development of shared undergraduate and graduate geoscience field-course and field-trip opportunities.Over the past decade, competing perspectives have emerged on the tectonic evolution of Cordilleran ocean-continent plate boundaries, including the geologic history of the Andes, the global archetype for Cordilleran convergent systems. Debate largely originates from contrasting emphases on different regions (forearc vs. retroarc) and different components (basins vs. magmatic arc vs. fold-thrust belt) of Cordilleran systems. This project will incorporate analytical techniques, such as sedimentary basin analysis, isotope geochemistry, petrology, and U-Pb geochronology, to identify potentially coupled episodic phases of basin evolution and arc magmatism that may be linked to internally driven orogenic processes (including underthrusting, high-flux magmatism, and buildup then foundering of crustal/lithospheric roots), or externally driven tectonic processes including fluctuating slab dynamics (cycles of subduction shallowing vs. steepening and associated rapid vs. diminished shortening and subsidence) and oceanic terrane accretion. Ecuador contains an important yet underappreciated record of tectonic quiescence or possible extension during what has been long regarded as uninterrupted Cenozoic shortening, thickening, and uplift along the entire Andean margin. Such a fluctuating pattern of mountain building may govern the structural and stratigraphic evolution of many ocean-continent convergent margins, with implications for the tectonic regimes of subduction and collisional systems.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.