Collaborative Research: Structural Constraints on Microcontinent Formation, Gulf of California

合作研究：加利福尼亚湾微大陆形成的结构约束

• 批准号: 1728690
• 负责人: Joann Stock
• 金额: $ 38.13万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1728690&HistoricalAwards=false
• 关键词: Collaborative; Research; Structural; Constraints; Microcontinent

When a continent rifts apart to form a new ocean basin, sometimes it breaks into two big pieces and a few smaller pieces called microcontinents. Microcontinents form early in the history of rifting, and afterwards they stay on one side of the rift, sink below sea level, and are buried by younger oceanic sedimentation. It is important to understand the development of microcontinent boundaries because these boundaries may host mineral deposits and hydrocarbons. We will do a field geology study of a young microcontinent that is above sea level, still actively forming, and bordered on two sides by active faults. We will test different models for the fault patterns and the timing of the uplift that caused its development. The field data we need to collect include: geological mapping of active faults; detailed study of elevations and ages of terraces that are offset by the faults; and mapping and sampling of nearby volcanic rocks to see if the volcanism was related to the rifting in terms of age or composition. Our study will help scientists to understand other, older microcontinents that are important in resource exploration, but are now buried by sediments and accessible only by drilling. Our team of investigators includes two female professors from the USA with their students, and collaborators from a Mexican research institute. During this study, we will train two graduate students in state-of-the art geological techniques including structure-from-motion, luminescence and/or cosmogenic radionuclide dating. This project will strengthen the international collaboration among the three institutions and train the graduate students in international field work. Research results will be incorporated into outreach activities including Spanish-language TV news interviews, annual teacher training workshops, an informational public display at Caltech, and public outreach events at UCLA. Multiple models have been proposed to explain microcontinent isolation in strike-slip settings. To test these models, we will examine the structures of a newly isolated, subaerial microcontinent of Isla Angel de la Guarda (IAG) in the northern Gulf of California. The IAG lies along the Pacific-North America plate boundary, and its southern tip contains a dense array of young continental faults. These cut a set of marine terraces within 20 km of a well-developed transform fault, along strike from a nascent spreading center. We will evaluate how the faults on IAG may be geometrically connected to the currently active plate boundary faults in the Ballenas Transform system as well as to former plate boundary faults in the Tiburon Basin to the SE of the island. We will constrain the timing and kinematics of the IAG faults through detailed geologic and structural mapping, topographic analysis using high resolution digital elevation mapping, and dating of geomorphic surfaces. During yearly field trips we will map bedrock types, fault geometry and structures, and geomorphic surface deformation, and collect samples for dating of bedrock, marine terraces, alluvial fans, and fault zones. Geological field work and image processing will be conducted jointly by researchers and students from Caltech, UCLA, and CICESE (Ensenada, Mexico). Samples collected in years 1 and 2 for dating geomorphic surfaces will be processed at UCLA using luminescence and/or cosmogenic radionuclide dating techniques. Bedrock samples will be geochemically analyzed at Caltech and dated by CICESE. The results of this study can transform our understanding of the early development of microcontinents, and our approach can be applicable to other microcontinents in the Atlantic, Indian, and Arctic oceans that have been targeted for resource exploration.

当大陆分裂形成新的海洋盆地时，有时它会分裂成两大块和一些较小的块，称为微大陆。 微大陆在裂谷历史的早期形成，之后它们停留在裂谷的一侧，沉入海平面以下，并被较年轻的海洋沉积物掩埋。了解微大陆边界的发展非常重要，因为这些边界可能蕴藏着矿藏和碳氢化合物。我们将对一个年轻的微大陆进行实地地质研究，该大陆位于海平面以上，仍在活跃形成，两侧与活动断层接壤。我们将测试不同的断层模式模型以及导致其发展的隆升时间。我们需要收集的现场数据包括：活动断层地质图；详细研究被断层抵消的阶地的海拔和年龄；对附近火山岩进行测绘和采样，以确定火山活动是否与裂谷的年龄或成分有关。我们的研究将帮助科学家了解其他更古老的微大陆，这些大陆对资源勘探很重要，但现在被沉积物掩埋，只能通过钻探才能到达。我们的研究团队包括两名来自美国的女教授及其学生，以及来自墨西哥研究所的合作者。 在这项研究期间，我们将培训两名研究生掌握最先进的地质技术，包括运动结构、发光和/或宇宙放射性核素测年。该项目将加强三个机构之间的国际合作，并培养研究生的国际实地工作。研究成果将被纳入外展活动中，包括西班牙语电视新闻采访、年度教师培训研讨会、加州理工学院的信息公开展示以及加州大学洛杉矶分校的公共外展活动。人们提出了多种模型来解释走滑环境中的微大陆隔离。为了测试这些模型，我们将检查位于加利福尼亚湾北部的天使德拉瓜达岛 (IAG) 新孤立的地下微大陆的结构。 IAG 位于太平洋-北美板块边界，其南端包含密集的年轻大陆断层。它们沿着新生扩张中心的走向，在距发育良好的转换断层 20 公里范围内切出了一组海洋阶地。我们将评估 IAG 上的断层如何与 Ballenas 变换系统中当前活跃的板块边界断层以及 Tiburon 盆地到岛屿东南部的前板块边界断层进行几何连接。我们将通过详细的地质和结构测绘、使用高分辨率数字高程测绘的地形分析以及地貌表面的测年来限制 IAG 断层的时间和运动学。在每年的实地考察中，我们将绘制基岩类型、断层几何形状和结构以及地貌表面变形的地图，并收集样本用于基岩、海洋阶地、冲积扇和断层带的测年。地质实地工作和图像处理将由加州理工学院、加州大学洛杉矶分校和 CICESE（墨西哥恩塞纳达）的研究人员和学生联合进行。在第一年和第二年收集的用于测年地貌表面的样本将在加州大学洛杉矶分校使用发光和/或宇宙放射性核素测年技术进行处理。基岩样本将在加州理工学院进行地球化学分析，并由 CICESE 进行测年。这项研究的结果可以改变我们对微大陆早期发展的理解，我们的方法可以适用于大西洋、印度洋和北冰洋中已成为资源勘探目标的其他微大陆。

项目成果

Structure of the Northern Altar Pull-Apart Basin Revealed by a 2D Reflection Seismic Survey: Evolution of the Gulf of California Shear Zone in Northwest Mexico

二维反射地震勘测揭示的北坛拉分盆地的结构：墨西哥西北部加利福尼亚湾剪切带的演化

• DOI: 10.1007/s00024-022-03138-1
• 发表时间: 2022
• 期刊: Pure and Applied Geophysics
• 影响因子: 2
• 作者: Huerta, Jorge Antonio;González-Escobar, Mario;Stock, Joann M.
• 通讯作者: Stock, Joann M.

Grand Canyon provenance for orthoquartzite clasts in the lower Miocene of coastal southern California

南加州沿海下中新统大峡谷正石英岩碎屑的物源

• DOI: 10.1130/ges02111.1
• 发表时间: 2019
• 期刊: Geosphere
• 影响因子: 2.5
• 作者: Sabbeth, Leah;Wernicke, Brian P.;Raub, Timothy D.;Grover, Jeffrey A.;Lander, E. Bruce;Kirschvink, Joseph L.
• 通讯作者: Kirschvink, Joseph L.