Geodynamic Framework for the Tectonic Trigger of Late Neogene Deformation in Southern Alaska

阿拉斯加南部新近纪晚期变形构造触发的地球动力学框架

• 批准号: 0537995
• 负责人: Magali Billen
• 金额: $ 23万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0537995&HistoricalAwards=false
• 关键词: Geodynamic; Framework; Tectonic; Trigger; Late

Various aspects of Late Neogene tectonics in southern Alaska, such as uplift along a weak transpressional boundary or transfer of plate boundary stresses to the continental interior, have been studied individually at other active margins. The superposition of these processes in southern Alaska provides a unique opportunity to quantify the relative importance and interaction of tectonic driving forces and plate structure using 3-D geodynamic models. This project has two components. The first part focuses on determining how pre-existing structural features (the slab shape, plate boundary coupling, narrow lithospheric-scale weak zones, and regional strength contrasts) interact to transfer and localize deformation in the continental interior. The results from the first part of the project provide the context in which to ask: What triggered the uplift of the Alaska Range 5 to 6 million years ago? This second part of the project tests two hypotheses for the tectonic trigger: a change in Pacific Plate motion or collision of the Yakutat Terrane, a small oceanic plateau that is currently accreting to and subducting in the Aleutian Trench. Predictions from 3-D time-dependent models are compared with the observational constraints on the timing and location of uplift of the Alaska Range and the regional distribution of deformation. This work will provide the first three-dimensional geodynamic model with which to test geologic hypotheses for the recent tectonic evolution of southern Alaska, and makes testable predictions for the onset of deformation in regions surrounding the Alaska Range where there are fewer observational constraints. The theory of plate tectonics assumes that interiors of plates are rigid and relative motion between plates occurs through deformation in a narrow plate boundary region. However, on continental margins that are under compression or extension, the regions of deformation can be broad or narrow, but far from the plate boundary. This study uses the observed deformation in southern Alaska to learn which structures in the continent determine the character of the deformation and will, consequently, broaden understanding of deformation in other convergent margins around the world. Three-dimensional visualization of the results are being integrated into undergraduate courses to teach students how to view and interpret complex three-dimensional structures and in public outreach activities. Planned displays at Denali National Park will incorporate simulation movies from this project.

阿拉斯加南部的新金元构造的各个方面，例如沿弱的转卸边界升高或将板边界应力转移到大陆内部的各个方面。这些过程在阿拉斯加南部的叠加提供了一个独特的机会，可以使用3-D地球动力学模型量化构造驱动力和板结构的相对重要性和相互作用。该项目有两个组件。第一部分的重点是确定预先存在的结构特征（平板形状，板边界耦合，狭窄的岩石圈尺度弱区和区域强度对比）如何相互作用，以在大陆内部的转移和局部变形相互作用。项目第一部分的结果提供了要问的背景：是什么引发了5至600万年前阿拉斯加范围的升高？该项目的第二部分测试了构造触发因素的两个假设：太平洋板块运动的变化或Yakutat Terrane的碰撞是一个小型海洋高原，目前正在阿留申式的沟渠中积聚并俯冲。将来自3-D时间依赖模型的预测与关于阿拉斯加范围隆升的时机和位置的观察性约束和变形的区域分布进行了比较。这项工作将提供第一个三维地球动力学模型，用于测试阿拉斯加南部最近构造的构造演化的地质假设，并为在较少观察力约束的地区围绕阿拉斯加范围的地区的变形开始做出可检验的预测。板块构造的理论假设板的内部是刚性的，板之间的相对运动是通过狭窄板边界区域的变形而发生的。但是，在压缩或延伸的大陆边缘上，变形区域可能是宽或狭窄的，但远离板边界。这项研究使用观察到的阿拉斯加南部的变形来了解非洲大陆的哪些结构决定了变形的特征，因此，将扩大对世界其他收敛缘变形的理解。结果的三维可视化正在整合到本科课程中，以教学学生如何查看和解释复杂的三维结构和公共外展活动。 Denali国家公园的计划展示将结合该项目的模拟电影。