Quaternary and Late Neogene Growth of the Cucomungo Canyon Restraining Bend and Associated Deformation Rates, Death Valley-Fish Lake Valley Fault System, Western Great Basin

西部大盆地死亡谷-鱼湖谷断层系库科蒙戈峡谷第四纪和新近纪晚期的抑制弯曲和相关变形率的生长

• 批准号: 1318727
• 负责人: John Geissman
• 金额: $ 39.74万
• 依托单位: University of Texas at Dallas
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1318727&HistoricalAwards=false
• 关键词: Quaternary; Late; Neogene; Growth; Cucomungo

This research project extends deformation rate estimates for the Death Valley-Fish Lake Valley transcurrent fault system, western Great Basin, to the last 5 million years with a stepwise resolution of 100,000 and possibly 10,000 years. The work will focus on a major restraining bend in the Death Valley-Fish Lake Valley fault system that formed as lateral displacement along the Death Valley-Fish Lake Valley fault was transferred to local shortening and uplift. The primary objectives are: (1) determination of deformation rates; (2) assessment of the role of discrete versus distributed deformation mechanisms; and (3) characterization of the three-dimensional geometry and evolution of structures and possible vertical-axis rotation during formation of the restraining bend. The project involves integration of detailed geologic mapping, structural analysis, stratigraphic characterization, geochronology, and magnetostratigraphic-paleomagnetic analysis. Field and laboratory studies will define the three-dimensional geometry, tectonic evolution, and mechanisms of deformation active during the formation of this major contractional structure. Assessment of deformation rates over different time intervals utilizes a robust chronostratigraphic framework and determination of aggregate and incremental displacements from deformation models. By combining high-precision 40Ar/39Ar age data for numerous key stratigraphic intervals (e.g. specific tephra layers and volcaniclastic deposits) with a magnetic polarity stratigraphy that can be correlated with the astrochronologically-tuned Neogene geomagnetic polarity timescale, temporal resolutions of 100,000 and possibly 10,000 years will be obtained. Combining this temporal information with field relations involving synorogenic strata and three-dimensional structural models allows resolution of incremental displacements of 100 to 1,000 meters during growth of the structure. With these displacement and timing ranges, the displacement and growth of the restraining bend provides rate determinations comparable to those for late Quaternary surface displacements.Accurate estimates of the rates of a broad range of geologic processes are critical to understanding the evolution of the Earth's surface over different time scales. The deformation of continents through the formation of faults and the release of seismic energy as earthquakes, in what is known as the earthquake cycle, is becoming better understood over durations of tens to tens of thousands of years and such information provides important insights into whether or to what degree earthquake activity remains the same through geologic time. Unfortunately, the ability to estimate deformation rates on major fault systems becomes more poorly resolved with the passage of time, mainly due to the obscuring effects of younger deformation and the inability to measure offset of well-dated marker units across faults. The capacity to estimate deformation rates over durations of tens of thousands and hundreds of thousands of years in most parts of the world remains elusive for periods of geologic time ranging from hundreds of thousands and millions of years. Enhanced understanding the earthquake cycle over durations of millions of years requires unraveling Earth's history over different time scales, and can be addressed only in rare instances where geologic structures are well preserved and provide the capacity to date geologic events with high- precision. The anticipated results of this research project will quantify the progressive development of a part of a major geologic fault system exposed within the broad, currently seismically active region that is the boundary between the eastern Sierra Nevada and the western Great Basin in the western US Cordillera. The Death Valley-Fish Lake Valley fault system has been active for several millions of years and records tens of kilometers of horizontal displacement. When compared to well determined contemporary and latest Quaternary deformation rate estimates established geodetically and from offset geomorphic features, the results of this study will help tie active tectonic to long-term deformation processes.

该研究项目将大盆地西部死亡谷-鱼湖谷横向断层系统的变形速率估计扩展到过去500万年，逐步分辨率为10万，可能为1万年。这项工作将集中在一个主要的限制弯曲在死亡谷-鱼湖谷断层系统，形成横向位移沿着死亡谷-鱼湖谷断层被转移到局部缩短和隆起。主要目标是：（1）确定变形速率;（2）评估离散变形机制与分布式变形机制的作用;（3）表征三维几何形状和结构演变，以及在约束弯曲形成期间可能的垂直轴旋转。该项目包括详细的地质测绘、构造分析、地层特征、地质年代学和磁性地层学-古地磁学分析的综合。野外和实验室研究将确定三维几何形状，构造演化，以及在这个主要的收缩结构形成过程中活动的变形机制。在不同的时间间隔的变形率的评估利用一个强大的年代地层框架和变形模型的总位移和增量位移的测定。通过将许多关键地层间隔（例如特定火山灰层和火山岩沉积物）的高精度40 Ar/39 Ar年龄数据与磁极性地层学相结合，可以与天文年代学调整的新近纪地磁极性时标相关联，将获得100，000年甚至可能10，000年的时间分辨率。将这一时间信息与涉及同造山地层和三维结构模型的场关系相结合，可以在结构生长期间分辨出100至1,000米的增量位移。有了这些位移和时间范围，位移和增长的限制弯曲提供速率测定媲美那些晚第四纪地表displacement.Accurate估计广泛的地质过程的速率是至关重要的，以了解地球表面的演变在不同的时间尺度。大陆通过断层的形成和地震能量的释放而变形，即所谓的地震周期，在数万年至数万年的持续时间内，人们越来越了解这些信息，这些信息为了解地震活动是否或在多大程度上保持不变提供了重要的见解。不幸的是，随着时间的推移，估计主要断层系统的变形速率的能力变得越来越差，主要是由于年轻的变形和无法测量跨断层的日期明确的标记单元的偏移的模糊影响。在世界大部分地区，估计数万年和数十万年的变形速率的能力在数十万年和数百万年的地质时期仍然难以捉摸。要加深对数百万年地震周期的理解，就需要解开地球在不同时间尺度上的历史，只有在地质结构保存完好并提供高精度地质事件日期的能力的罕见情况下才能解决。该研究项目的预期结果将量化目前地震活跃区（即内华达州东部山脉和美国西部科迪勒拉山脉西部大盆地之间的边界）内暴露的主要地质断层系统的一部分的逐步发展。死亡谷-鱼湖谷断层系统已经活动了数百万年，并记录了数十公里的水平位移。与根据大地测量和偏移地貌特征确定的当代和最新第四纪变形速率估计值相比，本研究的结果将有助于将活动构造与长期变形过程联系起来。