TIMING OF COOLING AND EXHUMATION OF LARAMIDE UPLIFTS INFORMS MODELS OF FLAT-SLAB SUBDUCTION

该项目旨在确定共同构成美国西部内陆落基山脉的主要山脉的抬升年龄。在地质文献中，这些山脉被称为“拉莱米隆起”，以怀俄明州拉勒米市和县的名字命名，该市和县位于这些隆起明显发育的地区。拉拉米德山脉的抬升时间知之甚少，但对于评估东太平洋盆地和北美板块西部地区构造板块的形状和运动方向至关重要。这项工作对公众来说很重要，原因有几个：(A)落基山脉是西部山区的决定性景观，200多年来一直激励着作家、艺术家、企业家、移民和科学家；然而，地质学家没有达成共识来解释这些山脉的起源。(B)由于其高海拔和南北朝向，这一壮观的景观影响了整个美国的生态和气候。(C)拉拉米德地区对美国具有巨大的经济重要性，蕴藏着具有重要战略意义的地下水、矿产和碳氢化合物资源。(D)虽然拉拉米勒隆起不再“活跃”，但该项目的成果将有助于了解当今地球上类似构造过程仍然活跃的地区(例如南美洲西部和阿拉斯加南部)的地震灾害。最后，一批本科生和研究生将在这个项目的背景下接受培训。这个项目的主要目标是确定蒙大拿州、怀俄明州和犹他州的拉莱姆隆起的挖掘时间。这对于了解拉拉米德造山的构造和地球动力学模型是至关重要的，通常认为拉拉米德造山是由平板俯冲作用造成的。这些模型在很大程度上依赖于拉莱姆隆起的时空模式。大洋高原和无震脊的平板式俯冲是区域高原隆升、弧形岩浆作用的终止和上覆板块地震活动的重要地球动力学现象。该项目将采用多组分测年方法，包括磷灰石裂变径迹和(U-Th-Sm)/He热年代学，当与热运动学模拟和沉积记录相结合时，将限制拉拉米德地区的冷却和侵蚀历史。隆起事件的时间和分布的区域模式将为美国西部的板块构造模型提供约束。通过这项研究获得的知识将被输出到其他活跃的和古老的平板构造体系，如阿拉斯加南部、中美洲和阿根廷西部。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project intends to determine the ages of uplift of the major mountain ranges that together constitute the Rocky Mountains of the western interior United States. These ranges are referred to in the geological literature as "Laramide uplifts", after the city and county of Laramie, Wyoming, which is situated in the region where these uplifts are notably developed. The timing of uplift of the Laramide ranges is poorly understood, but critical for assessing the shape and movement direction of tectonic plates in the eastern Pacific basin and western regions of the North American plate. This work is important to the public for several reasons: (a) The Rocky Mountains are the definitive landscape of the mountain west, a landscape that has inspired writers, artists, entrepreneurs, emigrants, and scientists for more than 200 years; yet, no consensus exists among geologists to explain the origins of these mountains. (b) By virtue of its high elevation and north-south orientation, this spectacular landscape impacts the ecology and climate of the entire U.S. (c) The Laramide region is of enormous economic importance to the U.S., containing strategically important groundwater, mineral, and hydrocarbon resources. (d) Although the Laramide uplifts are no longer "active", results of this project will useful for understanding seismic hazards in regions on Earth today where similar tectonic processes are still active (for example, western South America and southern Alaska). Finally, a group of undergraduate and graduate students will be trained in the context of this project.The primary objective of this project is to determine the timing of exhumation of Laramide uplifts in Montana, Wyoming and Utah. This is essential to inform tectonic and geodynamic models of the Laramide orogeny, which is generally attributed to flat-slab subduction. Such models rely heavily on spatio-temporal patterns of Laramide uplift. Flat-slab subduction of oceanic plateaus and aseismic ridges are important geodynamic phenomena in convergent margins, with respect to regional plateau uplift, termination of arc magmatism, and active seismicity in the overriding plate. This project will apply a multi-component dating approach, including apatite fission track and (U-Th-Sm)/He thermochronology, which, when combined with thermo-kinematic modeling and the record of sedimentation, will constrain the cooling and erosion histories of the Laramide region. Regional patterns in timing and distribution of uplift events will provide constraints for plate tectonic models of the western U.S. Knowledge gained by this research will be exportable to other active and ancient flat-slab tectonic systems such as southern Alaska, Central America and western Argentina.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.