Tectonic Evolution and Paleoclimatic History of the Basin and Range Province: New Constraints from Clumped-Isotope Thermometry

从中生代中期（大约一百万年前）到现在，北美西部科迪勒拉的地形在一个不同的隆升、挖掘和下降的历史中演变，部分原因是由于北美西部边缘的先收敛后转变运动。在这段时间间隔内，全球气候也发生了许多戏剧性的变化，包括从中生代-古近纪温室到新近纪两极有冰的世界的转变。气候变化在西科迪勒拉构造演化中的作用以及地形对古气候的影响已被广泛讨论。在这个项目中，稳定同位素地球化学的两项尖端技术将用于确定过去的温度和古水文，这将允许重建整个盆地北部和山脉省过去的海拔高度。过去温度和水文的变化将在三个关键的时间间隔内绘制出来——温暖的晚白垩世（大约7000万年前）和早始新世（大约5500万年前），以及相对凉爽的晚中新世（大约1000万年前）。在控制全球气候变化对地球化学记录的影响的同时，通过绘制不同时间片的同位素变化图，可以估计内陆地区过去的海拔高度。这种方法将解决关于北美西部构造史的悬而未决的问题，例如：在晚白垩纪，内华达州西部是否有一个非常高的高原，类似于现在的南美高原？始新世时期内华达山脉以东的地区海拔是低还是高？答案应该在整个地区的温度和同位素水文剖面中很清楚。高程是构造学的一个基本参数。因此，重建过去的海拔高度对于检验用来解释西科迪勒拉构造演化的地球动力学模型至关重要。除了对美国西部构造演化的限制外，这项研究将增加大陆古环境数据的增长体，这些数据对于比较计算机气候模拟的输出是至关重要的。随着新的模拟在更精细的空间尺度上发展，有类似尺度的古气候数据是必不可少的，特别是在地形起伏很大的地区。

From the middle Mesozoic (approximately million year ago) to the present, the topography of the western Cordillera of North America evolved in response to a diverse history of uplift, exhumation, and down-drop, due in part to first convergence and then transform motion along the western margin of North America. This time interval also saw many dramatic changes in global climate, including the transition from a Mesozoic-Paleogene greenhouse to a Neogene world with ice on the poles. The role of climate change in the tectonic evolution of the western Cordillera has been much discussed, as has the influence of topography on paleoclimate. In this project, two cutting-edge techniques from stable isotope geochemistry will be used to determine past temperatures and paleohydrology, which will allow reconstruction of past elevations across the northern Basin and Range Province. Variations in past temperature and hydrology will be mapped during three key time intervals - the warm Late Cretaceous (approximately 70 million years ago) and Early Eocene (approximately 55 million years ago), and the relatively cool Late Miocene (approximately 10 million years ago). By mapping isotopic variations at different time slices, past elevations at interior sites can be estimated while controlling for the effects of global climate change on geochemical records. This approach will address outstanding questions about the tectonic history of western North America, such as: Was there a very high plateau in western Nevada in the Late Cretaceous, analogous to the current South American Altiplano? Was the region east of the Sierra Nevada Mountains at low or high elevation during the Eocene? The answer should be clear in temperature and isotope hydrology profiles across the region.Elevation is a fundamental parameter in tectonics. Reconstructing past elevation is therefore critical for testing geodynamic models that have been proposed to explain the tectonic evolution of the western Cordillera. In addition to constraints on the tectonic evolution of the western U.S., this study will add to the growing body of continental paleoenvironmental data that are critical for comparison to output from computer climate simulations. As new simulations are developed at finer spatial scales, it is essential to have paleoclimatic data at a similar scale, particularly in regions with great topographic relief.