Quantification of Extensional Fault Processes and Landscape Response using Surface Exposure Dating

了解断层事件的位移累积速率和时间对于约束断层生长模型和活跃环境下的地震风险至关重要。以前的研究试图从定性的角度揭示断层的生长历史，但是由于缺乏合适的自然断层系统测年技术，限制了模型预测断层阵列发育过程中位移积累速率和速率变化的能力。这项工作结合了构造地质学、地貌学和地球化学的传统学科，对伸展断层阵列的演化和对变形的排水响应进行了定量分析。特别是，该研究涉及断层系统和相关排水的详细制图，与使用原位宇宙生成核素的地表暴露测年相结合，以确定断层从最初传播到物理连接的完整断层生长周期中的年表和断层生长速率。研究区位于犹他州东南部的峡谷地堑，在过去的0.5万年里，这里已经发生了伸展断裂，并且还在继续。它是这类研究的最佳区域之一，因为断层在各种断层相互作用的方向上都非常好地暴露出来，很容易观察到排水响应，并且暴露的岩性和时间尺度非常适合地表暴露测年。这项研究包括对航空照片和5米数字高程模型进行仔细的物理测绘，然后对断层连接带和相关的变形排水系统进行更详细的实地测绘。结合广泛的地表暴露测年研究，利用从富含石英的基岩样品中提取的铍-10、铝-26和碳-14，这种方法可以获得关于断裂时间和速率的独特定量信息。此外，河流变形将与位移积累的特定事件相关联，并将用于评估断层相关的断裂点在景观中退缩的机制和速率。这项研究的结果将首次通过横向断层传播的整个周期，通过相互作用和联系，提供一个完整的、定量的断层生长速率重建。反过来，这将大大提高对断层阵列演化基本过程的理解，从而提高地震风险评估和沉积盆地分析的可靠性。该研究还将对理解基岩通道侵蚀的侵蚀和大量沉积物的移除具有重要意义，基岩通道侵蚀被认为是山地地形构造演化的主导力量。

Understanding displacement accumulation rates and timing of fault events is crucial to constrain models of fault growth and seismic risk in active settings. Previous studies have attempted to unravel fault growth histories in a qualitative sense, but the lack of a suitable dating technique for natural fault systems has limited the models' ability to predict rates and variations in rate, of displacement accumulation during development of a fault array. This work unites the traditional disciplines of structural geology, geomorphology and geochemistry in a quantitative analysis of extensional fault array evolution and drainage response to deformation. In particular, the study involves detailed mapping of fault systems and associated drainages, in tandem with Surface Exposure Dating using in-situ cosmogenic nuclides, to determine chronology and rates of fault growth during the complete cycle of fault growth from initial propagation to physical linkage.The study area is located in the Canyonlands Graben of southeastern Utah, where extensional faulting has occurred in the last 0.5 m.y. and is ongoing. It is one of the finest areas for this type of investigation, as the faults are exceptionally well exposed in a variety of fault interaction orientations, drainage responses are readily observed, and the exposed lithology and time scale is very appropriate for Surface Exposure Dating.The research involves careful physical mapping on aerial photographs and a 5-meter Digital Elevation Model, followed by more detailed field mapping of fault linkage zones and associated deformed drainage systems. Combined with an extensive Surface Exposure Dating study using in-situ Berylium-10, Aluminum-26 and Carbon-14 extracted from quartz-rich bedrock samples along stream beds and fault scarps, this approach yields unique quantitative information about the timing and rates of faulting. In addition, fluvial deformation will be correlated to specific events of displacement accumulation and will be used to evaluate the mechanisms and rates of fault-related knickpoint retreat through the landscape. The results of this research will provide, for the first time, a complete, quantitative reconstruction of fault growth rates through the entire cycle of lateral fault propagation, through interaction and linkage.This, in turn, will significantly improve the understanding of the fundamental processes underlying fault array evolution and thus increase the reliability of seismic risk assessments and sedimentary basin analysis. The research will also have important implications for understanding erosion and mass sediment removal through bedrock channel erosion, which is considered a governing force in the tectonic evolution of mountainous terrains.