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

从中生代中生代(大约百万年前)到现在，北美西部科迪勒拉的地形演化是对不同的隆升、折返和下降历史的响应，部分原因是首先汇聚，然后沿着北美西缘转换运动。这段时间间隔也见证了全球气候的许多戏剧性变化，包括从中生代-古近纪温室过渡到两极有冰的新近纪世界。气候变化在科迪勒拉西部构造演化中的作用以及地形对古气候的影响一直是人们讨论的重点。在该项目中，将使用稳定同位素地球化学的两项尖端技术来确定过去的温度和古水文，这将使重建整个北部盆地和山脉省过去的海拔高度成为可能。过去温度和水文的变化将在三个关键时间间隔内绘制出来--晚白垩世温暖(约7000万年前)和始新世早期(约5500万年前)，以及相对凉爽的中新世晚期(约1000万年前)。通过绘制不同时间片上的同位素变化图，可以估计内陆地区过去的海拔，同时控制全球气候变化对地球化学记录的影响。这种方法将解决有关北美西部构造史的悬而未决的问题，例如：在晚白垩世，内华达州西部是否有一个非常高的高原，类似于现在的南美洲高原？始新世时，内华达山脉以东的地区是处于低海拔还是高海拔？答案应该在整个地区的温度和同位素水文剖面上是明确的。海拔是构造学的一个基本参数。因此，重建过去的高程对于检验地球动力学模型至关重要，这些模型被提出用来解释西部科迪勒拉的构造演化。除了对美国西部构造演化的限制外，这项研究还将增加越来越多的大陆古环境数据，这些数据对于与计算机气候模拟的结果进行比较至关重要。随着新的模拟在更精细的空间尺度上发展，拥有类似尺度的古气候数据是至关重要的，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.