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被称为东加州剪切带的更广泛的形变区域，该区域包含活动和不活动的部分。该项目调查不活跃的东加州剪切带中的断层，以限制随着时间的推移断层的时间尺度和类型。这些信息将有助于理解板块边界的构造收窄和非活动段的遗弃，这对限制南加州孕震断裂的演化具有重要意义。该项目结合了野外研究、详细的断层分析和地质年代学，研究了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，他们大多来自西班牙裔人口，他们每个人都将在开展科学和科学交流方面获得宝贵的经验。学生还将参与当地地球科学活动的外展机会，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裂系统提供，较少但相当大的部分发生在被称为东加州剪切带(ECSZ)的广泛分布形变区内。ECSZ可以细分为目前占相对板块运动的20%-25%的活动段，以及今天基本上不活动的古ECSZ。该项目的目标是通过实地研究、结构分析和地质/热年代学对与古ECSZ演化形成同时代的具有良好特征的熊峡谷砾岩(BCC)进行研究，以限制古ECSZ内变形的时间尺度和样式。盖层的40Ar/39Ar年龄与体心立方碎屑的40Ar/39Ar结合，将制约沉积的时间标尺。基岩的热年代学结合断层岩的构造和薄片分析将记录随着古ECSZ的活动而变化的应变场，而断裂方解石的U-Pb定年将约束断裂作用的时间尺度。记录这段有点神秘的早期历史，对于理解ECSZ向活动带的构造收窄和古ECSZ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中以西班牙裔为主的人口。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外展机会将被用来与社区和社区大学建立关系。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.