Collaborative Research: The great Alaskan escape room: Has Northern Cordilleran escape tectonics fluctuated with time and why?

合作研究：伟大的阿拉斯加逃生室：北科迪勒拉逃生构造是否随时间波动？为什么？

• 批准号: 2218920
• 负责人: Sean Regan
• 金额: $ 14.92万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2218920&HistoricalAwards=false
• 关键词: Collaborative; Research; great; Alaskan; escape

The proposed research will address how plate tectonics causes fragments of continents to “chip off” and move along the continental margin to a new location, often thousands of kilometers away from where they formed. This process has been termed tectonic escape and has played an essential role in shaping the mountainous terrain in western North America over the last ~100 million years. Professors Waldien and Regan will study this tectonic phenomenon by unraveling the geologic evolution and uplift history of the Ahklun Mountains in western Alaska because this region is the northernmost extent of continental fragments that have moved northward along western North America. The study will test the hypothesis that magmatism and uplift in the Ahklun Mountains is related to temporal fluctuations in the amount of tectonic escape over the last ~70 million years. Due to the remote location and inherent relationship between rural communities and the western Alaska landscape, the project will be used to train first-generation college student geologists from first-people communities in Alaska and South Dakota (locations of host institutions). All personnel working on the project will participate in public outreach presentations at Wood-Tikchick State Park emphasizing the relationship between the bedrock geology and the unique landscape of western Alaska.Escape tectonics is commonly evoked in collisional systems to aid in orogenic space limitations by translating crustal material away from collisional indenter(s). In accretionary orogens however, strike-slip deformation develops in response to oblique relative plate motion and results in the translation of forearc slivers. If persistent over prolonged time, the accumulated strike-slip displacement may manifest as forearc escape. Accretionary orogens present a challenge to classical models of escape tectonics because the obliquity of relative plate motion and the broad wavelength geometry of strike-slip faults can change over the duration of orogenesis, thus the proportion of plate motion taken up as escape may vary greatly through time. The 3-year project intends to test the long-proposed model of Cordilleran escape tectonics by documenting the Cretaceous-Cenozoic offset and deformation history along the southwestern terminal onshore segment of the Denali fault system in the Ahklun Mountains of western Alaska. Key questions addressed by the study will include: 1) Do reactivated suture zone faults in the Ahklun Mountains and associated extensional magmatism together represent a partitioned obliquely convergent margin that was active during an escape regime? 2) Do structures inherited from the assembly of the Cordillera focus strike-slip and/or shortening during the downscaling of escape? 3) Is the transition out of a primary escape tectonics regime recorded by the uplift/exhumation of the Ahklun mountains? and 4) Does the timing of reduced escape tectonics correspond with suggested Paleocene-Eocene oroclinal bending of southern Alaska? PIs Waldien and Regan will pursue answers to these questions by employing regional geologic mapping, structural analysis, petrography, thermochronology, geochronology, and geochemistry in a series of focus areas within the Ahklun Mountains to 1) determine the timing of and cause of magmatism and rock exhumation in the Ahklun Mountains, 2) identify offset markers that may be used to restore Denali fault strike-slip displacement at different time intervals, and 3) couple the fault restoration and timing of exhumation/magmatism to regional tectonic processes operating at the scale of the orogen. Results from this study will test whether tectonic escape was steadfast or fluctuated along the Cretaceous-Cenozoic Denali fault system and identify the tectonic scenario(s) associated with transitions among primarily indentation, rotation, and escape regimes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

拟议的研究将解决板块构造如何导致继续的碎片“切碎”，并沿着连续的边缘移动到一个新位置，通常距离它们形成的地方数千公里。这一过程被称为构造逃生，在过去的大约1亿年中，在北美西部的山区地形中发挥了至关重要的作用。 Waldien教授和Regan教授将通过揭开阿拉斯加西部Ahklun山脉的地质进化和隆升历史来研究这种构造现象，因为该地区是沿北美西部向北移动的连续碎片的最大范围。该研究将检验以下假设：艾哈卢山脉中的岩浆和隆升与过去〜7000万年的构造逃逸量的暂时波动有关。由于农村社区与阿拉斯加西部景观之间的偏僻地点和继承关系，该项目将用于培训来自阿拉斯加和南达科他州第一人民社区的第一代大学学生地质学家（东道国的地点）。所有从事该项目的人员将参加伍德 - 锡克奇州立公园的公共外展演讲，强调基岩地质与西阿拉斯加西部独特景观之间的关系。在碰撞系统中，通常会引起埃斯卡普构造学的唤起，以通过将外壳材料转换为collasional collisional intenter（S）。然而，在增生的牛根中，滑滑变形响应于倾斜的相对板运动，并导致前臂​​载玻片的翻译。如果在长时间的时间内持续存在，则累积的滑移位移可能表现为前臂逃生。增生性牛根对逃生构造的经典模型提出了挑战，因为相对板运动的斜率和走滑断层的宽波长几何形状可能会在造口的持续时间内发生变化，因此，随着时间的推移，逃生的板运动比例可能会发生很大变化。这项为期三年的项目旨在通过记录沿西部阿拉斯加Ahklun山脉的Denali断层系统的西南终端沿西南航站楼的白垩纪 - 甲基苯二酚的偏移和变形历史来测试山脉逃生构造的长期模型。研究解决的关键问题将包括：1）Ahklun山脉中的重新激活的缝合区断层和相关的延伸岩浆作用共同代表一个在逃生状态期间活跃的倾斜倾斜边缘？ 2）在逃生降低降低期间，从山脉焦点滑滑的组装和/或缩短的结构是否？ 3）是否通过Ahklun山脉的隆起/挖掘记录的主要逃生构造制度过渡？ 4）减少的逃生构造的时间是否与阿拉斯加南部南部的形成古新世临床弯曲相对应？ PIS Waldien和Regan将通过采用区域地质映射，结构分析，岩石学，热量教学，地球学学和地球化学的区域地质映射和地球化学区域中的一系列焦点区域来追求这些问题的答案时间间隔和3）将挖掘/岩浆作用的断层恢复和时机与以造山量的规模运行的区域构造过程。这项研究的结果将测试沿白垩纪 - 甲状腺元素故障系统的构造逃生是坚定的还是波动的，并确定与主要凹痕，旋转和逃生方案之间过渡相关的构造场景。该奖项反映了NSF的法定任务，并通过评估了基金会的智力效果，以诚实地支持了基金会的诚实支持。