CAREER: Paleotopography using Clumped Isotopes in the Basin and Range: Refining the Three Dimensional Evolution of a Continental Extensional Province

美国西部的盆地和山脉省可能是当今地球上暴露得最好、最容易接近的大陆内伸展省的例子。尽管各种各样的地质和地球物理证据表明，自中新世中期以来，该地区经历了大约200%的东西延伸，但盆地和山脉今天被典型（30公里）厚度的大陆地壳所覆盖，但其平均海拔（1-1.5公里）大大高于基于简单地球物理计算的预期。盆地和山脉的大陆地壳是如何在整个新生代进化到今天的特征的，这是一个悬而未决的问题，它直接关系到远离板块边界的扩散大陆变形的性质，以及导致地壳拉伸和变薄而不破裂以产生新的海洋盆地的过程。各种构造模型被用来解释盆地和山脉的演化，但地质观测结果无法区分这些模型。这些模型之间的一个潜在区别是它们对美国西部古海拔历史的预测。利用湖相碳酸盐的团块同位素来测定古温度计的最新进展，提供了一种从地质记录中确定古温度的新方法，从而间接地确定了碳酸盐形成的古海拔。通过应用这些新方法测量盆地和山脉一套低海拔、近海平面的湖相碳酸盐岩与同期湖相碳酸盐岩之间的温差，本项目将为盆地和山脉在整个新生代演化过程中地形的时空演化提供新的约束条件，从而解决盆地和山脉构造演化的几个关键问题，包括：(1)伸展前盆地和山脉是否为高原？(2)如果存在高原，其空间范围是多大？(3)晚新生代伸展期盆地和山脉的高程是如何变化的？(4)晚新生代有哪些大幅度伸展活动？这项研究将通过与自然历史展览博物馆和密歇根大学3d实验室合作，开发和制作一部关于板块构造的全穹顶天文馆电影，纳入针对大底特律地区初中生的教育和推广计划。初中早期是许多学生开始对科学失去兴趣的时候。这个教育项目将把从这个项目中收集到的研究数据，以及从其他正在进行的国家科学基金会项目（如Earthscope）中收集到的丰富的地质和地球物理数据，整合成一部完全沉浸式的电影，讲述地球的历史、推动板块构造的过程、与板块边界相关的危险，以及我们可以应用于研究现代板块运动的技术。该电影将被纳入每年有3000 - 6000名学生参加的展览博物馆的地球科学推广日，旨在让学生将科学视为一个活跃和不断发展的研究领域。通过开发新的和引人入胜的方式来展示地球科学，展示发现的兴奋元素和社会相关性，吸引了许多研究地球的人，该项目旨在提高学生在中学及以后对STEM科目的参与。

The Basin and Range province of the western United States is perhaps the best exposed and most accessible example of an intracontinental extensional province on Earth today. Although a variety of lines of geological and geophysical evidence indicate that this region has experienced approximately 200% east-west extension since middle Miocene time, the Basin and Range is underlain today by continental crust of typical (30 km) thickness, but that lies at an average elevation (1-1.5 km) substantially higher than one would expect based on simple geophysical calculations. How the continental crust of the Basin and Range has evolved throughout Cenozoic time to have the characteristics that it has today is an outstanding question that bears directly on the nature of diffuse continental deformation, far away from plate boundaries, and the processes that lead the crust to stretch and thin without rupturing to create new oceanic basins. A variety of tectonic models have been invoked to explain the evolution of the Basin and Range, but the geologic observations that would allow one to discriminate between these models are unresolved. One potential discriminant between these models is the predictions each makes for the paleoelevation history of the western United States. Recent advances in the development of paleo-thermometers, using clumped isotopes in lacustrine carbonates, offers a new approach to determining paleotemperatures from the geologic record, and thus, indirectly the paleoelevations at which the carbonates formed. By applying these new methods to measure the temperature differences between a suite of low-elevation, near sea-level lacustrine carbonates, and coeval lacustrine carbonates in the Basin and Range, this project will develop new constraints on the temporal and spatial evolution of topography across the Basin and Range throughout its Cenozoic evolution, and thus address several key questions about the tectonic evolution of the Basin and Range, including: (1) Was the Basin and Range a high-standing plateau prior to extension?; (2) What was the spatial extent of such a plateau, if it existed?; (3) How did the elevation of the Basin and Range change during late Cenozoic extension?; and (4) What processes accommodated large-magnitude extension in late Cenozoic time?This research will be incorporated into an education and outreach program directed at early middle-school-aged students in the Greater Detroit area through the development and production of a full-dome planetarium movie on plate tectonics, in collaboration with the Exhibit Museum of Natural History and the 3DLabs at the University of Michigan. Early in middle school is the time when many students begin to lose interest in science. This educational project will incorporate the research data gathered from this project, along with the wealth of geological and geophysical data being collected from other ongoing NSF projects, such as Earthscope, into a fully immersive film on the history of the Earth, the processes that drive plate tectonics, the hazards associated with plate boundaries, and the technology we can apply to study modern plate motions. This movie will be incorporated into outreach days on earth sciences at the Exhibit Museum, which reach 3,000-6,000 students annually, and which are designed to get students to think of science as an active and evolving field of study. By developing new and engaging ways of presenting earth science that demonstrate the elements of excitement of discovery and societal relevance that draw in so many who study the earth, the project aims to increase the participation of students in STEM subjects through middle school and beyond.