Investigating the nature and timing of development of the Eastern California shear zone (ECSZ) in southeastern California

太平洋板块和北美板块之间的边界包括圣安德烈亚斯断层和一个被称为东加利福尼亚剪切带的更广泛的变形区域，其中包括活跃板块和不活跃板块。该项目研究了不活跃的东加利福尼亚剪切带的断层，以限制断层的时间尺度和样式。这一信息将有助于了解板块边界的结构变窄和非活动板块的放弃，这对限制南加州地震断层的演化具有重要意义。该项目结合现场研究、详细的断层分析和地质年代学，研究在非活动段演化过程中变形的岩石。为此，该项目将包括一个由研究生、本科生和社区大学学生组成的团队，这些学生主要来自西班牙裔人口，他们每个人都将获得开展科学和科学交流的宝贵经验。学生还将有机会参加当地的地球科学活动，与社区互动。横跨太平洋-北美板块边界的相对变换运动由圣安德烈亚斯断层系统调节，其中较小但相当大的一部分发生在被称为东加利福尼亚剪切带（ECSZ）的广泛分布变形带内。ECSZ可以细分为活跃板块，目前占相对板块运动的20-25%，以及今天大部分不活跃的古ECSZ。本研究的目的是通过野外考察、构造分析和地热年代学研究，对与古鄂西盆地演化同期形成的具有良好特征的熊峡谷砾岩（BCC）进行研究，确定古鄂西盆地的变形时间尺度和类型。地层的40Ar/39Ar健康年龄与BCC的40Ar/39Ar碎屑健康年龄相结合，将限制沉积的时间尺度。基底岩的热年代学结合断层岩的构造和薄片分析将记录古东断带活动时应变场的变化，断层方解石的U-Pb定年将约束断裂的时间尺度。记录这段略显神秘的早期历史，对于理解东中国海的构造变窄为活动带和古东中国海的放弃至关重要。该项目将资助研究生和本科生，他们将反映UTEP主要的西班牙裔人口。学生将在野外工作、结构分析、地质/热年代学、建模技术和科学交流方面获得宝贵的经验。当地地球科学活动的拓展机会将被用来建立与社区和社区大学的关系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The boundary between the Pacific and North American plates includes the San Andreas fault and a wider region of deformation called the Eastern California shear zone, which contains active and inactive segments. This project investigates faults in the inactive Eastern California shear zone to constrain the timescales and styles of faulting through time. This information will help to understand the structural narrowing of the plate boundary and abandonment of the inactive segment, which is important for constraining the evolution of earthquake-producing faults in southern California. This project combines field studies, detailed fault analysis, and geochronology to study rocks that were deformed during evolution of the inactive segment. To do this, the project will include a team of graduate, undergraduate, and community college students from a largely Hispanic population who will each gain valuable experience in conducting science and scientific communication. Students will also be involved with outreach opportunities at local earth science events to interact with the community. Relative transform motion across the Pacific-North America plate boundary is accommodated by the San Andreas fault system, with a lesser, but substantial, portion occurring within a broad zone of distributed deformation known as the Eastern California shear zone (ECSZ). The ECSZ can be subdivided into an active segment that currently takes up 20-25% of the relative plate motion, and a paleo-ECSZ that is largely inactive today. The goal of this project is to constrain the timescales and styles of deformation within the paleo-ECSZ through field studies, structural analysis, and geo/thermochronology applied to the well-characterized Bear Canyon conglomerate (BCC) that formed coeval with evolution of the paleo-ECSZ. 40Ar/39Ar sanidine ages on tephra layers coupled with detrital sanidine 40Ar/39Ar of the BCC will constraint timescales of deposition. Thermochronology of basement rocks coupled with structural and thin section analysis of fault rocks will document changing strain fields as the paleo-ECSZ became active, and U-Pb dating of fault calcite will constrain timescales of faulting. Documenting this somewhat cryptic earlier history is crucial for understanding structural narrowing of the ECSZ into an active belt and abandonment of the paleo-ECSZ. This project will fund graduate and undergraduate students who will reflect the largely Hispanic population of UTEP. Students will gain valuable experience with field work, structural analysis, geo/thermochronology, modeling techniques, and scientific communication. Outreach opportunities at local earth science events will be used to build relationships with the community and community college.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.