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

加利福尼亚州的内华达山脉高山有多久了？这个问题是揭开北美地质史最持久的挑战之一。许多研究认为，内华达山脉在白垩纪晚期(约6500万至1亿年前)达到高海拔，随后经历了有限的地表海拔上升。一系列相反的研究认为，始新世(约3500万至5500万年前)内华达山脉海拔低，地势弱，始新世后与上新世地壳根部剥离有关的地表抬升脉冲导致了该山脉的现代抬升。这些不同的观点体现了北美构造演化的根本不同理论。解释内华达山脉自始新世以来一直是一个持续高地势的地区的主要证据来源是稳定同位素和叶形古海拔测量技术。然而，最近的一系列大气动力学研究对这些解释提出了挑战。这些研究表明，目前用于解释降水同位素比替代记录的框架是基于关于大气的假设，这些假设对内华达山脉通常不适用，或者没有适当考虑到古气候变化。该项目的目标是融合地球动力学研究、大气动力学和古气候模拟的最新方法，以显著改进对内华达山脉古测高数据的解释，从而促进对该山脉表面高程历史的了解。该项目将在一系列大气条件下严格评估内华达山脉周围的气团轨迹以及相关的降水同位素和焓分布。这些数据将来自水同位素大气环流模型对始新世至今的古气候情景的模拟，以及这段时间内北美西部一系列拟议的地形环境。其结果将改善对整个新生代内华达山脉地形的定量约束，特别是对晚新生代地表隆起的潜力。拟议的研究是一种新的跨学科构造方法，利用现代大气模拟技术，并将它们应用于最长期存在的地质学问题之一--内华达山脉的地表隆起历史。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。将开发一套解释古高程测量代理记录的新技术，这些技术将在世界各地的各种环境中使用。一旦在内华达山脉有限的背景下得到证实，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，并在古气候记录中解开混合的海拔/气候信号。这项研究的结果将引起大气科学界的兴趣，因为它将增进我们对几种古气候情景下静态稳定性的了解，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界产生重要影响。

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.