Collaborative Proposal: Relation of Exhumation to Lithsopheric Architecture Along a Steep Continental Margin, Idaho-Oregon

该项目的目的是确定地形隆起、侵蚀和挖掘、预先存在的地质边界以及驱动变形的底层地幔动力学之间的联系。野外区域为爱达荷州西部的鲑鱼河缝合带，是爱达荷州大部分地区下伏的前寒武纪北美洲与俄勒冈州蓝山较年轻（显生宙）增生地体之间的边界。爱达荷岩基只在这条边界的北美一侧形成。碰撞后和持续的变形对该地区不同部位的影响不同，这代表了现有地质构造和/或深层驱动力的差异。各种山脉隆起的时间、速率和数量将与当前的地下几何形状有关——利用地震数据确定——以识别地球的运动。地壳和地幔在区域尺度上抬升了地形。这项工作需要结合地震数据分析，以提供详细的地下结构，以及热年代学，以确定从深处隆起和挖掘岩石的时间，以及当前地形的发展。这项工作横跨三个主要研究领域，包括一个最终的项目综合：1)记录爱达荷州基底亚特兰大叶的挖掘路径，以确定它是否受到年轻岩浆作用的抬升；2)沿横切爱达荷岩基的反查利斯断裂带潜在差别化发掘评价；3)在蓝山进行挖掘的记录，以便将其历史与邻近的北美进行比较。特别值得关注的是，萨蒙河缝合带是否因哥伦比亚河后玄武岩伸展而被重新激活。将热年代学和地震结果与最近的地质学、地质年代学和地球化学研究相结合，可以综合区域构造演化，并可以阐明继承岩石圈结构与活动构造过程之间的关系。佛罗里达大学和弗吉尼亚理工大学的两名研究生和两名本科生直接得到了这项工作的支持。构造综合将涉及所有三所机构的研究生，其中一些由其他来源资助。

The aim of this project is to determine the link between topographic uplift, erosion and exhumation, pre-existing geologic boundaries, and the underlying mantle dynamics that drive deformation. The field area is the Salmon River suture zone of western Idaho, which is the boundary between Precambrian North America underlying most of Idaho and younger (Phanerozoic) accreted terranes of the Blue Mountains in Oregon. The Idaho batholith formed exclusively on the North American side of this boundary. Post-collision and ongoing deformation affect different parts of the region differently, representing differences in pre-existing geologic structure and/or in deep driving forces. The timing, rates, and amounts of uplift of the various mountain ranges will be related to the current subsurface geometry -- determined using seismic data -- to identify motions in the Earth?s crust and mantle that elevated topography on regional scales. The work entails a combination of seismic data analyses, to provide a detailed sub-surface architecture, and thermochronology, to determing the timing of uplift and exhumation of rocks from depth and the development of the current topography.The work spans three main study areas and includes a final project synthesis: 1) Documentation of the exhumation path of the Atlanta lobe of the Idaho batholith to determine if it was uplifted by younger magmatism; 2) Evaluation of potential differential exhumation along the trans-Challis fault zone that cross-cuts the Idaho batholith; and 3) Documentation of exhumation in the Blue Mountains, in order to compare its history to that of adjacent North America. A particular focus is whether the Salmon River suture zone was reactivated by post-Columbia River Basalt extension. The combination of the thermochronology and seismic results with recent geology, geochronology, and geochemistry studies will allow synthesis of a regional tectonic evolution and can illuminate the relationship between inherited lithospheric structures and active tectonic processes.Two graduate and two undergraduate students at the University of Florida and Virginia Tech are directly supported by this work. Tectonic synthesis will involve graduate students at all three institutions, several of whom are funded by other sources.