Collaborative Research: Anatomy of a Greenhouse World: The Early Eocene of the Green River Basin, Wyoming

过去环境变化的地质记录提供了对地球自然系统行为的启发性一瞥。 在古代湖泊中形成的沉积物在这方面特别有用，原因有几个：它们对气候变化高度敏感;它们通常包含相对完整的地质档案，空白相对较少;它们可能被用来记录随着时间的推移发生的对人类有意义的变化。 美国西部的绿色河地层提供了一个特别有价值的记录，记录了大约5000万至5300万年前始新世时期的最新地质时期的长期温室条件。 它以其丰富的脊椎动物、昆虫和植物化石组合而闻名，并以拥有世界上最大的苏打灰和油页岩商业矿床而闻名。 该研究项目将重点关注这段时间反复快速变暖事件的证据，通过研究河道如何变化，湖泊内积累的沉积物类型以及古代土壤发育和化学的变化。 同样重要的是，这项研究将根据湖中火山灰的新放射性测定日期、地球磁场变化的年表以及地球自转和轨道周期性振荡驱动的沉积模式，为这些重要矿床建立一个前所未有的准确度和精确度的时间尺度。 该提案的更广泛影响将包括为初中和高中学生开发当地2小时的实地考察，通过在便携式设备上使用创新的数据可视化技术来加强。 早始新世气候适宜期（EECO）是一个全球持续变暖的时期，其原因仍然不完全确定。 绿色河组的湖泊沉积物保存了丰富的和以前未开发的记录，补充了海洋沉积物中所含的记录，并提供了一个机会，以提高早始新世时间尺度的精度和准确性。 该项目是一个综合的、多学科的调查，重点是世界上最丰富和研究最好的古湖泊地层系统之一。本研究将探讨三个主要问题：1。陆地变暖的时间与海洋记录推断的时间以及地球轨道变化的预测模式相比如何？ 放射性同位素测年的最新进展可用于直接测试变暖事件与地球轨道变化的关系，并将太阳系的动态引力模型校准到约1000年。五千万年2.在EECO期间，陆地上的温度、季节性、水文循环和风化是如何演变的？一种假设是，相对于海洋，大陆的变暖被放大，并伴随着全年更稳定的温度，而降水的季节性和强度增加。3.北美西部复杂的构造和岩浆演化如何影响EECO气候信号的保存？ 该研究将测试的假设，反复，逐步排水重组内构造活跃的高地修改的水文平衡和沉积沉积物的始新世湖泊环境和其响应的轨道changes.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

The geologic record of past environmental change offers an illuminating glimpse into the behavior of Earth's natural systems. The deposits formed in ancient lakes are particularly useful in this regard for several reasons: they are highly sensitive to climate change; they often contain relatively complete geologic archives with relatively few gaps; and they can potentially be used to document changes that occurred over time scales meaningful to humans. The Green River Formation in the western U.S. offers an especially valuable record of the most geologically recent period of prolonged greenhouse conditions, which occurred approximately 50-53 million years ago during the Eocene Epoch. It is famous for its rich assemblages of fossil vertebrates, insects, and plants, and for containing the world's largest commercial deposits of soda ash and oil shale. This research project will focus on evidence for repeated rapid warming events during this time, by examining how river courses changed, the types of sediment that accumulated within the lake, and variations in ancient soil development and chemistry. Equally important, this study will build a time scale of unprecedented accuracy and precision for these important deposits, based on new radiometric dates of volcanic ash in the lake, the chronology of changes in the Earth's magnetic field, and sedimentation patterns that were driven by periodic oscillations in the Earth's rotation and orbit. Broader impacts of this proposal will include development of local 2-hour field trips for middle and high school students, enhanced through the use of innovative data visualization technology on portable devices. The Early Eocene Climatic Optimum (EECO) was a time of persistent global warmth, of which the cause remains incompletely determined. Lake deposits of the Green River Formation preserve a rich and previously untapped record that complements that contained in marine sediments, and present an opportunity to advance the precision and accuracy of the Early Eocene timescale. This project is an integrated, multidisciplinary investigation focused on one of the world's richest and best studied systems of ancient lake strata. The research will investigate three principal questions: 1. How did the timing of terrestrial warming compare to that inferred from the marine record, and to predicted patterns of the Earth's orbital variations? Recent advances in radioisotopic dating can be used to directly test the relationship of warming events to Earth's orbital changes, and calibrate dynamic gravitational models of the solar system back to ca. 50 million years. 2. How did temperatures, seasonality, hydrologic cycling, and weathering on land evolve during the EECO? One hypothesis is that warming was amplified on continents relative to the oceans and was accompanied by more equable temperatures year-round, whereas precipitation seasonality and intensity increased. 3. How did the complex tectonic and magmatic evolution of western North America impact the preservation of EECO climate signals? The research will test the hypothesis that repeated, stepwise drainage reorganizations within the tectonically-active uplands modified the hydrologic balance and sedimentary deposits of the Eocene lake environment and its response to orbital changes.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.