Cenozoic Migration of Topography in the North American Cordillera Recorded in Coupled Basin-Detachment Systems

本课题组正在对北部盆地、山脉及邻近落基山脉内的盆地-变质核复核对进行古高程研究，以重建该地区新生代的海拔历史，并检验有关伸展动力的相互矛盾的假说。基于这些假设的构造模型可以广泛地与三种相互竞争的地表隆起和伸展机制联系起来：(1)黄石热点羽流在岩石圈底部的撞击，(2)地幔岩石圈的分层，(3)重力势能梯度驱动的浮力相关流动。这些模型中的每一个都预测了不同的、可测试的地形响应。利用稳定同位素方法重建了蒙大拿、内华达和犹他州变质岩心杂岩及其邻近盆地的新生代古海拔历史。这项古海拔测量研究将提供一套独特的约束条件，结合地球物理和地质数据集，将更好地理解北部盆地和山脉以及北美科迪勒拉新生代扩张背后的驱动力。本研究项目建立在先前对美国西部变质岩心复合体和山间盆地的古高程研究的基础上，这些研究表明，北美西部的地形发展具有时空变化的历史，地表隆起随时间向南迁移。在地球上的所有大陆上都有巨大的山脉。然而，这些山脉是如何形成的，仍然是地球科学中难以捉摸的问题之一。了解山脉的地形历史对于评估不同的构造模式以及确定山脉的生长如何影响气候变化至关重要。对于新生代（地球历史的最后6500万年）来说尤其如此，因为有人提出，大型新生代山带的构造，如喜马拉雅/西藏和北美西部的科迪勒拉山脉，改变了地球的气候。本文利用稳定同位素古高程法研究了美国西部科迪勒拉地区的新生代地形和气候历史，并对该地区已提出的构造模式进行了评价。它将提供关于美国西部山脉如何形成的新见解，以及山脉生长与气候之间联系和反馈的关键信息。

This research group is conducting a paleoaltimetry study of basin-metamorphic core complex pairs within the northern Basin and Range and contiguous Rocky Mountains in order to reconstruct the Cenozoic elevational history of this region and to test competing hypotheses of the driving forces for extension. Tectonic models based on these hypotheses can be broadly associated with three competing surface uplift and extension mechanisms: (1) impingement of the Yellowstone hot spot plume at the base of the lithosphere, (2) delamination of mantle lithosphere, and (3) buoyancy-related flow driven by gradients in gravitational potential energy. Each of these models predicts distinct and testable topographic responses. Cenozoic paleoelevation history is being reconstructed for metamorphic core complexes and adjacent basins in Montana, Nevada, and Utah using stable isotope methods. This paleoaltimetry study will provide a unique set of constraints, which combined with geophysical and geologic data sets, should yield a better understanding of the driving forces behind Cenozoic extension in the northern Basin and Range and the North American Cordillera. This research project builds upon previous paleoelevation studies of metamorphic core complexes and intermontane basins in the western United States that suggest a history of spatially and temporally varying topographic development of western North America with surface uplift migrating southward with time.Large mountain ranges are found on all the Earth's continents. How these mountain ranges grow, however, remains one of the more elusive questions in earth sciences. Understanding the topographic history of mountain ranges is critical for evaluating different tectonic models as well as determining how the growth of mountains affects climate change. This is particularly true for the Cenozoic (last 65 million years of Earth's history) because it has been proposed that the construction of the large Cenozoic mountain belts, such as the Himalaya/Tibet and western North America Cordillera, have altered the Earth's climate. This study examines the Cenozoic topographic and climate history of the western U.S. Cordillera using stable isotope paleoaltimetry and evaluates the tectonic models that have been proposed for this region. It will provide new insights regarding how the American western mountain ranges formed as well as critical information on the links and feed-backs between growth of mountain ranges and climate.