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

厄瓜多尔在建造安第斯山脉的过程中记录了与俯冲有关的岩浆作用和构造环境。这项研究将讨论构造旋回和洋壳的吸积在调节沿大洋-大陆俯冲边缘的岩浆作用、地壳增厚和盆地沉降期中的作用。该项目将把跨越几个沉积盆地的区域导线的结果与安第斯山脉最窄的厄瓜多尔境内的岩浆活动记录结合起来。将使用一系列分析技术来确定盆地发展、沉积物来源和过去的排水系统的重大转变的时间，并识别地壳增厚的时期、岩浆源的变化以及洋壳吸积的影响。这项研究将提供对海洋-大陆俯冲板块边界沿线的地质过程和地质灾害的见解，提供将通过改进风险评估和基础设施规划而造福社会的信息。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野外课程和实地考察机会。在过去十年中，关于科迪勒洋陆板块边界的构造演化出现了相互竞争的观点，包括安第斯山脉的地质史，安第斯山脉是科迪勒会聚系统的全球原型。争论主要源于对科迪勒系统不同区域(弧前与弧后)和不同组成部分(盆地与岩浆弧与褶皱冲断带)的不同侧重点的对比。该项目将采用沉积盆地分析、同位素地球化学、岩石学和铀-铅地质年代学等分析技术，以确定盆地演化和弧岩浆活动的潜在耦合幕式阶段，这些阶段可能与内部驱动的造山作用(包括逆冲作用、高通量岩浆作用和地壳/岩石圈根部的堆积然后下沉)或外部驱动的构造过程有关，其中包括波动的板片动力学(俯冲变浅与变陡和相关的快速与减弱缩短和下沉的旋回)和大洋地体的增生作用。厄瓜多尔有一个重要但被低估的记录，即在整个安第斯边缘一直被认为是不间断的新生代缩短、增厚和隆升期间，构造平静或可能的伸展。这种起伏不定的造山模式可能会支配许多大洋-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制度产生影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.