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.

阿拉斯加南部晚第三纪构造的各个方面，例如沿着弱压扭边界的隆升或板块边界应力向大陆内部的转移，在其他活动边缘已被单独研究。这些过程在阿拉斯加南部的叠加提供了一个独特的机会，量化的相对重要性和相互作用的构造驱动力和板块结构使用3-D地球动力学模型。该项目有两个组成部分。第一部分的重点是确定如何预先存在的结构特征（板片形状，板块边界耦合，狭窄的岩石圈规模的弱区，区域强度对比）相互作用，转移和本地化的变形在大陆内部。该项目第一部分的结果提供了一个问题的背景：是什么引发了500万到600万年前阿拉斯加山脉的隆起？该项目的第二部分测试了构造触发的两个假设：太平洋板块运动的变化或雅库塔特地体的碰撞，雅库塔特地体是一个小的海洋高原，目前正在阿留申海沟中增生和俯冲。从3-D的时间依赖性模型的预测进行了比较的时间和位置的隆起的阿拉斯加山脉和变形的区域分布的观测约束。这项工作将提供第一个三维地球动力学模型，以测试地质假说最近的构造演化的阿拉斯加南部，并作出可测试的预测开始变形的阿拉斯加山脉周围地区，那里有较少的观测限制。板块构造理论假设板块内部是刚性的，板块之间的相对运动是通过狭窄的板块边界区域的变形发生的。然而，在处于挤压或伸展状态的大陆边，变形区可宽可窄，但远离板块边界。这项研究使用在阿拉斯加南部观察到的变形，了解大陆的结构决定了变形的特点，因此，将扩大对变形的理解在世界各地的其他收敛边缘。结果的三维可视化正在被纳入本科课程，以教学生如何查看和解释复杂的三维结构，并在公共宣传活动中。计划在德纳利国家公园的展览将包括这个项目的模拟电影。