Collaborative Research: Investigating Controls on Temporal-spatial Heterogeneous Deformation Along a Transpressive Strike-slip Fault System: The Eastern Denali Fault Corner

合作研究：研究沿挤压走滑断层系统时空非均质变形的控制：东迪纳利断层角

• 批准号: 1550034
• 负责人: Kenneth Ridgway
• 金额: $ 19.77万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1550034&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Controls; Temporal

The 2,000 km long Denali Fault is a major active fault system in Alaska that bounds crustal blocks, which slide past each other in a horizontal fashion. The fault has a long and complicated history over the past 65 million years. Due to its complex and curved geometry, there are portions of the fault where the motion of the blocks is oblique to the fault trend resulting in the formation of basins and fold and thrust belts. In this project, a research team from Purdue University, Syracuse University, and the University of Alaska are studying a portion of this fault to better understand the factors that control how these crustal blocks deform. They are particularly interested in determining whether the strength of the blocks on opposite sides of the fault or the geometry of the fault controls deformation. There are many large active fault systems like the Denali around the world and it is important to understand how these behave since many are capable of generating significant earthquakes such as the 2002 magnitude 7.9 earthquake on the Denali Fault. Additional desired societal outcomes of the study include full participation underrepresented minorities in STEM through support of Native American students and researchers and outreach to Alaskan Native American communities plus development of a globally competitive STEM workforce through undergraduate and graduate student training.Transitional zones between primarily strike-slip motion and oblique convergence are a common feature along strike-slip faults. Deformation along these transpressive faults is controlled in part by both the obliquity of the applied stress and fault geometry (variation in strike and dip), and rheologic contrasts across the faults on the lithospheric- and crustal-scale. These transpressive fault regions offer insight into how strain is accommodated and also how the broad zones defined by thrust belts and foreland basins evolve along strike-slip fault systems as crustal blocks are translated along regions of varying obliquity. The east-central Denali fault segment has a generally simple geometry of unvarying strike and dip for about 120 km, lies between two large composite terranes of contrasting strength, and has a documented history of vertical tectonics during the Cenozoic. Thus, it serves as a natural laboratory to study the affect of these two distinct boundary conditions on the history of deformation along this active strike-slip fault system. This project will examine the importance of fault geometry relative to contrasts in lithospheric strength across faults on the heterogeneity of deformation along the eastern corner of the Denali fault. The Denali fault in this region changes from dominantly strike-slip to a transpressive regime. The competing hypotheses (strength vs. geometry) on how strain is accommodated and deformation occurs along this transpressive fault system will be tested by integrating thermochronology, geochronology, structural, and basin analysis studies. Detrital (modern river sediment and from strata) and bedrock thermochronology (K-feldspar 40Ar/39Ar, apatite fission-track and apatite (U-Th)/He) north and south of the Denali fault will track spatial and temporal patterns of exhumation in conjunction with basin development along the fault as proxies and recorders for deformational processes. 40Ar/39Ar and fission track tephrachronology, palynology, and vitrinite reflectance will delineate timing of basin subsidence, inversion, thermal history, and shortening rates. 40Ar/39Ar and U-Pb geochronology on clasts from conglomerate and sand samples will provide insight into paleo-drainage patterns and displacement of sediment sources from basins along the fault. Together, these integrated data will yield important new constraints on the relative contributions two common boundary conditions play in heterogeneous deformation patterns along a continental strike-slip fault system.

2,000公里长的德纳里断层是阿拉斯加的一个主要活动断层系统，它界定了地壳块体，这些块体以水平方式相互滑动。该断层在过去的6500万年里有着漫长而复杂的历史。由于其复杂和弯曲的几何形状，有部分断层的块体运动是倾斜的断层趋势，导致盆地和褶皱和冲断带的形成。在这个项目中，来自普渡大学、锡拉丘兹大学和阿拉斯加大学的一个研究小组正在研究这个断层的一部分，以更好地了解控制这些地壳块体如何变形的因素。他们特别感兴趣的是确定断层两侧的块体强度或断层的几何形状是否控制变形。世界上有许多像德纳里这样的大型活动断层系统，重要的是要了解这些断层系统的行为，因为许多断层系统能够产生重大地震，如2002年德纳里断层上的7.9级地震。该研究的其他预期社会成果包括通过支持美洲原住民学生和研究人员以及与阿拉斯加美洲原住民社区的联系，充分参与STEM中代表性不足的少数民族，以及通过本科生和研究生培训发展具有全球竞争力的STEM劳动力。主要走滑运动和斜向会聚之间的过渡区是沿着走滑断层的共同特征。沿着这些逆冲断层的变形部分受控于外加应力和断层几何形状（走向和倾角的变化）以及岩石圈和地壳尺度上断层之间的流变对比。这些逆冲断层区域提供了对应变如何被调节以及由逆冲带和前陆盆地限定的广阔区域如何随着地壳块体沿着不同韧性区域平移而沿着走滑断层系统演化的深入了解。Denali中东部断层段具有大致简单的几何形状，走向和倾角不变，约120公里，位于两个强度对比明显的大型复合断层之间，并且在新生代期间具有有记录的垂直构造历史。因此，它作为一个天然的实验室，研究这两个不同的边界条件的影响，变形历史的沿着这个活动的走滑断层系统。该项目将研究断层几何形状相对于岩石圈强度对比的重要性，断层对迪纳利断层沿着东角变形的不均匀性。该地区的德纳里断层从走滑为主的转换机制。将通过整合热年代学、地质年代学、构造和盆地分析研究来测试关于应变如何适应和变形如何沿沿着该逆冲断层系统发生的相互竞争的假设（强度与几何形状）。德纳里断层以北和以南的碎屑（现代河流沉积物和地层）和基岩热年代学（钾长石40 Ar/39 Ar、磷灰石裂变径迹和磷灰石（U-Th）/He）将跟踪折返的空间和时间模式，并与沿着断层的盆地发展一起作为变形过程的代理和记录器。40 Ar/39 Ar和裂变径迹年代学、孢粉学和镜质体反射率将描述盆地沉降、反转、热历史和缩短速率的时间。砾岩和砂岩碎屑的~（40）Ar/~（39）Ar和U-Pb年代学研究，将为研究古水系格局和沉积物源从沿着断裂盆地的迁移提供重要信息。总之，这些综合数据将产生重要的新的约束的相对贡献，两个共同的边界条件发挥非均质变形模式沿着大陆走滑断层系统。