EAR-PF: Unravelling climate and tectonic signatures using a landscape evolution modelling framework to interpret stable isotope and thermochronology records

当地质学家使用岩石回到过去了解地球过去的样子时，要区分气候和构造(即造山)的相互竞争的影响可能是一件具有挑战性的事情。例如，在巴塔哥尼亚北部的安第斯山脉，科学界之前注意到了一些观测结果，表明该地区在中新世时期变得更加寒冷和干燥。但是，很难知道这种明显的寒冷气候是因为巴塔哥尼亚北部安第斯山脉在中新世处于高海拔(导致当地气候变冷)，还是当地环境对全球气候变化做出了反应。这个博士后奖学金有两个主要部分。在第一部分中，Pi Havranek将使用三种不同的地球化学工具，所有这些工具都是在过去15-20年内开发的，每一种工具都可以揭示中新世北巴塔哥尼亚安第斯山脉气候和构造系统的不同方面。由于Pi Havranek打算使用的工具是如此之新，对这些类型的数据的解释一直是相互独立的。为了能够一起解释它们，皮哈夫拉内克将创建一个景观演变模型。这类模型旨在描述地貌(如山脉)随时间变化的方式。该模型将能够根据不同的假设气候和构造情景来预测地球化学数据应该是什么。然后就有可能评估哪一种假设最适合所有的地球化学数据。这个项目的最终目标是阐明哪个先出现，是使巴塔哥尼亚北部安第斯山脉得以生长的寒冷气候，还是使当地气候变冷的山脉隆起。如果成功，这种方法可能会推广到世界各地。作为与该项目相关的实地工作的一部分，PiHavranek将为拉普拉塔大学的学生主持一个关于稳定同位素地球化学的短期课程。为了使这个项目使用的现场和实验室环境更容易进入，Pi Havranek将制作一系列关于这些空间的视频参观。通过爱达荷州大学向上跳跃三人激励计划招募的两名高中生将帮助评估这些视频，并使广大观众能够接触到它们。地球科学界很早就认识到，气候和构造通过侵蚀和景观演变相互联系和反馈。在地质时间尺度上，构造可以通过硅酸盐风化来调节气候，气候可以通过控制风化和侵蚀的程度来影响地壳深部的过程。要弄清岩石记录中观察到的主要驱动因素--气候或构造--尤其具有挑战性。例如，如果古环境随着时间的推移而冷却，这种冷却可能是由地表抬升或全球气候冷却驱动的。许多地球化学家开发的替代工具都是针对气候和构造问题而开发的，这些问题要么针对过去的气候条件，要么针对岩石挖掘的速度。此外，地球化学替代数据经常被孤立地解释，以独立地约束气候和构造历史，而不考虑它们的同时演化。在这个项目中，目的是共同解释巴塔哥尼亚安第斯山脉(阿根廷丘布特省)北部帕索德尔萨波盆地的气候和构造历史。位于阿根廷安第斯山脉破碎前陆的Paso del Sapo盆地提供了一个独特的机会，可以开发一个整合热年代学、稳定同位素地球化学和景观演化模拟的框架，因为那里有很好的地质背景记录，并且存在明确的、可验证的构造和气候假说。Pi Havranek将使用碳酸盐块状同位素测温和火山玻璃稳定同位素地球化学创造古气候记录，以及2)使用低温热年代学(碎屑磷灰石(U-Th)/He)进行折返。然后，Pi Havranek将创建一个能够预测稳定同位素地球化学和低温热年代学数据的景观演化模型。这个模型将被用来检验之前提出的关于帕索德尔萨波盆地的构造和气候假说。该项目将为未来稳定同位素和热年代学的耦合研究提供一个可靠的框架。该项目将支持：1)在拉普拉塔大学实施稳定同位素地球化学短期课程；2)创建可访问的地球科学教育视频；3)通过爱达荷州大学的三人激发向上跳跃计划指导两名高中生。该项目由地球科学博士后奖学金计划和既定的激励竞争研究计划(EPSCoR)共同资助。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。

When geologists use rocks to go back in time to understand what Earth was like in the past, it can be challenging to pull apart the competing effects of climate and tectonics (i.e. mountain building). For example, in the Northern Patagonian Andes, the scientific community has previously noted observations that indicate the region got colder and drier during the Miocene Epoch. But, it is hard to know if that apparent cold climate is because the Northern Patagonian Andes were at high elevations in the Miocene (causing the local climate to be cold) or if the local environment was responding to changes in global climate. There are two major portions of this postdoctoral fellowship. In the first part, PI Havranek will use three different geochemistry tools, all of which were developed in the last 15 – 20 years, that can each shed light on different aspects of the climate and tectonics system of the Northern Patagonian Andes in the Miocene. Because the tools PI Havranek intends to use are so new, the interpretation of these kinds of data has always been done separately from each other. To be able to interpret them together, PI Havranek will create a landscape evolution model. These kinds of models are intended to describe the ways that landforms (like mountain ranges) change through time. The model will be capable of predicting what the geochemical data should be based on different hypothesized climate and tectonic scenarios. Then it is possible to evaluate which hypothesis best fits all of the geochemical data. The final goal of this project is to shed light on which came first, a cold climate that enabled the growth of the Northern Patagonian Andes, or the uplift of a mountain range that locally cooled the climate. If successful, this kind of approach could be extended to different places around the world. As a part of the field work associated with this project, PI Havranek will lead a short course on stable isotope geochemistry for students at Universidad de La Plata. To make both the field sites and laboratory settings used for this project more accessible, PI Havranek will produce a series of video tours of those spaces. Two high-school students, recruited through the University of Idaho Upward Bound TRIO-INSPIRE program will help assess the videos and make them accessible to a wide range of viewers.The geoscience community has long recognized that climate and tectonics are inextricably linked and feedback on each other via erosion and landscape evolution. Over geologic timescales, tectonics can modulate climate through silicate weathering, and climate can influence deep-crustal processes by controlling the extent of weathering and erosion. It is particularly challenging to disentangle the primary driver, climate or tectonics, of observations in the rock record. For example, if a paleoenvironment cooled over time, that cooling could be driven by either surface uplift or by cooling of the global climate. Many of the proxy tools geochemists have developed to target questions about climate and tectonics target either past climatic conditions or rates of rock exhumation. Furthermore, geochemical proxy data are frequently interpreted in isolation to independently constrain either climatic and tectonic histories without considering their concurrent evolution. In this project, the aim is to co-interpret the climatic and tectonic history of the Paso del Sapo Basin in the Northern Patagonian Andes (Chubut Province, Argentina). The Paso del Sapo basin in the Broken Foreland of the Argentine Andes provides a unique opportunity to develop a framework for integrating thermochronology, stable isotope geochemistry, and landscape evolution modeling because there is a well-documented geologic context, and clear, testable tectonic and climatic hypotheses exist. PI Havranek will create a record of 1) paleoclimate using carbonate clumped isotope thermometry and volcanic glass stable isotope geochemistry and 2) exhumation using low temperature thermochronology (detrital apatite (U-Th)/He). Then, PI Havranek will create a landscape evolution model capable of predicting both stable isotope geochemistry and low temperature thermochronology data. This model will be used to test previously proposed tectonic and climatic hypotheses of the Paso del Sapo Basin. This project would provide a proven framework for future coupled stable isotope and thermochronology studies. The project will support: 1) the implementation of a stable isotope geochemistry short course at Universidad de La Plata; 2) the creation of accessible geoscience education videos; and 3) mentorship of two high school students through the University of Idaho TRIO-INSPIRE Upward Bound Program.This project is jointly funded by the Earth Sciences Postdoctoral Fellowship program and the Established Program to Stimulate Competitive Research (EPSCoR).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.