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100万年前）到现在，北美西部科迪勒拉山脉的地形演变响应于不同的历史隆起，折返，下降，部分原因是第一次收敛，然后转换运动沿着北美西部边缘。在这段时间里，全球气候也发生了许多戏剧性的变化，包括从中生代-古近纪的温室转变为新第三纪的两极结冰世界。气候变化在西科迪勒拉山脉构造演化中的作用已被广泛讨论，地形对古气候的影响也是如此。在该项目中，将使用稳定同位素地球化学的两种尖端技术来确定过去的温度和古水文学，这将有助于重建整个北方盆地和山脉省过去的海拔高度。过去的温度和水文变化将在三个关键时间段进行测绘-温暖的晚白垩世（约7000万年前）和早始新世（约5500万年前），以及相对凉爽的晚中新世（约1000万年前）。通过绘制不同时间片的同位素变化图，可以估计内部站点过去的海拔高度，同时控制全球气候变化对地球化学记录的影响。这种方法将解决悬而未决的问题，北美西部的构造历史，如：有一个非常高的高原在西部内华达州在晚白垩世，类似于目前的南美高原？始新世时，内华达州山脉以东的地区是处于低海拔还是高海拔？这个问题的答案在该地区的温度和同位素水文剖面图中应该是清楚的。海拔是构造的一个基本参数。因此，重建过去的海拔是至关重要的测试地球动力学模型，已提出解释西科迪勒拉的构造演化。除了对美国西部构造演化的限制外，这项研究将增加不断增长的大陆古环境数据，这些数据对于与计算机气候模拟的输出进行比较至关重要。由于新的模拟是在更精细的空间尺度上开发的，因此必须有类似尺度的古气候数据，特别是在地形起伏较大的地区。

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.