Collaborative Research: Improved Cenozoic Paleoelevation Estimates for the Sierra Nevada, California: Linking Geodynamics and the Atmospheric Sciences

加州的内华达州山脉有多久了？这个问题是解开北美地质历史的最持久的挑战之一。许多研究认为，内华达州山脉在白垩纪晚期（约6500万至1亿年前）达到高海拔，随后经历了有限的表面海拔上升。一系列相反的研究认为，始新世（约3500万至5500万年前）的内华达州山脉海拔低，地形起伏弱，始新世后的地表隆起脉冲与上新世地壳根的分层有关，导致了该山脉的现代海拔。这些不同的观点体现了北美大地构造演化的根本不同理论。解释内华达州山脉自始新世以来一直是一个持续高地形区域的主要证据来源是稳定同位素和叶状古测高技术。然而，最近的一系列大气动力学研究挑战这些解释。这些研究表明，目前的框架解释降水同位素比值的代理记录是基于对大气的假设，一般不适用于塞拉利昂内华达州或不考虑适当的古气候变化。该项目的目标是将来自地球动力学研究、大气动力学和古气候建模的最新方法相结合，以大幅改善对内华达州山脉古高度数据的解释，从而促进对该山脉地表高程历史的理解。该项目将严格评估内华达州山脉周围的气团轨迹以及一系列大气条件下的相关降水同位素和焓分布。这些将来自于套件的水同位素启用大气环流模型模拟的古气候情景，从始新世到现在，并为一系列拟议的地形设置北美西部在此期间。其结果将是改善定量约束的地形上的整个新生代的内华达州，特别是对晚新生代的地表隆起的潜力。拟议的研究是一个新的，跨学科的方法构造，利用现代大气建模技术，并将其应用于最持久的地质问题之一，表面隆起的历史上的内华达州。虽然这种方法利用了动力气象学和同位素地球化学技术，但其结果将直接影响我们对北美地质演化的理解。将开发一套解释古测高代用记录的新技术，这些技术将在世界各地广泛使用。一旦在内华达州的有限范围内得到证实，这些技术可以应用于其他地区和时间间隔，以更好地解释隆升历史和解开混合海拔/气候信号在古气候记录。这项研究的结果将是感兴趣的大气科学界，因为它将推进我们的知识的静态稳定性在几个古气候情景，并将阐明地形和气候之间的非线性相互作用。因此，这项研究将对固体地球和气候变化社区产生重要影响。

How long have California's Sierra Nevada Mountains been high? This question is one of the most persistent challenges in unraveling the geological history of North America. Many studies argue that the Sierra Nevada reached high elevation by the Late Cretaceous (about 65 to 100 million years ago) and experienced subsequent limited surface elevation increases. An opposing array of studies argue that the Eocene (about 35 to 55 million years ago) Sierra Nevada had low elevation and weak relief and that a post-Eocene pulse of surface uplift linked to the Pliocene delamination of a crustal root led to the modern elevation of the range. These divergent views embody fundamentally different theories of North American tectonic evolution. The primary sources of evidence for the interpretation that the Sierra Nevada have been a region of persistent high topography since the Eocene are stable isotope and leaf-shape paleoaltimetry techniques. However, a series of recent atmospheric dynamics studies challenge these interpretations. These studies show that current frameworks for interpreting proxy records of precipitation isotopic ratios are based on assumptions about the atmosphere that are not generally valid for the Sierra Nevada or that do not take proper account of paleoclimate variation. The goal of this project is to merge the latest methods from geodynamical studies, atmospheric dynamics, and paleoclimate modeling, to substantially improve interpretations of paleoaltimetric data from the Sierra Nevada and thereby advance understanding of the surface elevation history of the range. The project will rigorously evaluate air parcel trajectories around the Sierra Nevada and associated precipitation isotopic and enthalpy distributions for a range of atmospheric conditions. These will be derived from suites of water-isotope enabled atmospheric General Circulation Model simulations of paleoclimate scenarios from the Eocene through the present, and for a range of proposed topographic settings for western North America over that interval. The result will be improved quantitative constraints on the topography of the Sierra Nevada throughout the Cenozoic and in particular on the potential for Late Cenozoic surface uplift.The proposed study is a new, interdisciplinary approach to tectonics that leverages modern atmospheric modeling techniques and applies them to one of the most persistent problems in geology, the surface uplift history of the Sierra Nevada. While the approach draws on dynamical meteorology and isotope geochemistry techniques, the results will directly impact our understanding of the geological evolution of North America. A suite of new techniques for interpreting paleoaltimetry proxy records that will be of use in a wide range of settings around the world will be developed. Once proven in the limited context of the Sierra Nevada, these techniques can be applied to other regions and time intervals to better interpret uplift histories and disentangle the mixed elevation/climate signals in paleoclimate records. The results of this study will be of interest to the atmospheric sciences community because it will advance our knowledge of static stability in several paleoclimate scenarios and will elucidate the nonlinear interactions between topography and climate. This study will thus have important implications for both the solid earth and climate change communities.