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 公里长的迪纳利断层是阿拉斯加的一个主要活动断层系统，它限制了地壳块体，这些块体以水平方式滑过彼此。该断层在过去6500万年里有着悠久而复杂的历史。由于其复杂且弯曲的几何形状，断层的某些部分的块体运动与断层走向倾斜，从而形成盆地、褶皱带和冲断带。在这个项目中，来自普渡大学、雪城大学和阿拉斯加大学的研究小组正在研究该断层的一部分，以更好地了解控制这些地壳块变形的因素。他们特别感兴趣的是确定断层相对两侧块体的强度或断层的几何形状是否控制变形。世界各地有许多像德纳里断层这样的大型活动断层系统，了解这些断层系统的行为非常重要，因为许多断层系统都能够产生重大地震，例如 2002 年德纳里断层上发生的 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向阿拉斯加美洲原住民社区进行推广，以及通过本科生和研究生培训培养具有全球竞争力的 STEM 劳动力，使代表性不足的少数群体充分参与 STEM。滑动运动和倾斜收敛是走滑断层的共同特征。沿这些压断层的变形部分受到所施加应力的倾斜度和断层几何形状（走向和倾角的变化）以及断层在岩石圈和地壳尺度上的流变对比的控制。这些压断层区域提供了关于如何适应应变的见解，以及当地壳块体沿着不同倾斜度的区域平移时，由冲断带和前陆盆地定义的广阔区域如何沿着走滑断层系统演化的见解。中东部迪纳利断层段总体上具有简单的几何形状，其走向和倾角持续约 120 公里，位于两个强度对比较大的复合地体之间，并有新生代垂直构造历史记录。因此，它是研究这两种不同边界条件对沿该活动走滑断层系统变形历史的影响的天然实验室。该项目将研究断层几何形状相对于断层岩石圈强度对比对德纳利断层东角变形不均匀性的重要性。该地区的迪纳利断层从走滑为主转变为压断带。关于如何沿着该压断层系统适应应变和发生变形的相互竞争的假设（强度与几何形状）将通过整合热年代学、地质年代学、结构和盆地分析研究来测试。德纳利断层北部和南部的碎屑（现代河流沉积物和地层）和基岩热年代学（钾长石 40Ar/39Ar、磷灰石裂变径迹和磷灰石 (U-Th)/He）将跟踪德纳利断层北部和南部折返的空间和时间模式。与沿断层的盆地发育相结合，作为变形过程的代理和记录器。 40Ar/39Ar 和裂变径迹年代学、孢粉学和镜质体反射率将描绘盆地沉降、反转、热史和缩短率的时间。对砾岩和砂样本中的碎屑进行 40Ar/39Ar 和 U-Pb 地质年代学研究将有助于深入了解古排水模式和沿断层盆地沉积物源的位移。总之，这些综合数据将对两个常见边界条件在沿大陆走滑断层系统的异质变形模式中的相对贡献产生重要的新约束。