Collaborative Research: Testing the Role of Transtension in Continental Rupture: An Integrative Study of the Sonoran Margin and Tiburón Basin, Northern Gulf of California

合作研究：测试相变在大陆破裂中的作用：对加利福尼亚湾北部索诺兰边缘和蒂布隆盆地的综合研究

• 批准号: 0739017
• 负责人: Michael Oskin
• 金额: --
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-02-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0739017&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Role; Transtension

Development of strain partitioning in transtensional rifts may play a significant role in localizing continental rupture. Partitioning of extension and dextral shear in the proto-Gulf of California during Late Miocene time (12 to 6 million years ago) remains a fundamental unresolved problem that hinders understanding of the initial conditions for ocean basin formation. Preliminary evidence from coastal Sonora is supportive of a regional model that promotes dextral transtension in a zone of uncertain width prior to localization of plate-boundary motion in the Gulf of California approximately 6 million years ago. It is not known whether Late Miocene dextral shear was sufficiently fast or focused to alter rheological conditions and change the mode of rifting from distributed Basin-and-Range-style extension to localized lithospheric necking, subsidence, and continental rupture. In this project U.S. and Mexican scientists aim to constrain the structural distribution of dextral shear over time during localization of the plate boundary. Specifically, they will determine whether late Miocene transtension in the proto-Gulf of California was accommodated by diffuse 3-dimensional strain in a wide zone of coeval strike-slip and normal faults or occurred in a narrow zone of discrete dextral faults and/or rotating blocks embedded within a broader zone of East-West extension. To discriminate between these models, the team is investigating the geologic structure and basin development of the Sonoran continental margin, including adjacent Isla Tiburon and the offshore Sonora shelf by: (1) documenting the distribution of dextral shear through detailed structural mapping and paleomagnetic analysis; (2) quantifying transtensional strain rates using structural reconstructions, 40Ar/39Ar dating of intercalated volcanic rocks, and subsidence analysis of syntectonic sedimentary and volcanic basins; and (3) integrating the onshore geologic record with offshore structures and basins by interpretation of existing multi-channel seismic data from the offshore Tiburon basin.The Gulf of California provides an excellent natural laboratory for studying processes of continental break-up. Previous studies have shown that warm continental crust tends to resist localized deformation, which is required for rupture of continental lithosphere. Data from this study will improve understanding of how and why the warm crust of western North America ruptured to form the Gulf of California, which has been opening since about 6 million years ago. This project is supported by the EAR Tectonics Program, the NSF Office of international Science and Engineering, and the NSF/OCE MARGINS program. The research involves significant participation of graduate and undergraduate students, collaboration with Native Americans, and strong international partnerships with research institutions in Mexico.

拉张裂谷中应变分配的发展可能在大陆破裂局部化中发挥重要作用。中新世晚期（12至600万年前）原始加利福尼亚湾的伸展和右旋剪切的划分仍然是一个尚未解决的基本问题，阻碍了对洋盆形成初始条件的理解。来自索诺拉沿海地区的初步证据支持了一种区域模型，该模型在大约 600 万年前加利福尼亚湾板块边界运动定位之前，在宽度不确定的区域中促进了右旋张量。目前尚不清楚晚中新世右旋剪切是否足够快或集中以改变流变条件并将裂谷模式从分布式盆山式延伸转变为局部岩石圈颈缩、沉降和大陆破裂。在该项目中，美国和墨西哥科学家的目标是在板块边界定位过程中限制右旋剪切力随时间的结构分布。具体来说，他们将确定原加利福尼亚湾的中新世晚期张紧是否是由同时期走滑和正断层的宽阔区域中的扩散三维应变所调节的，还是发生在离散右旋断层和/或嵌入更广泛的东西延伸区域内的旋转块的狭窄区域中。为了区分这些模型，该团队正在研究索诺拉大陆边缘的地质结构和盆地发育，包括邻近的蒂布龙岛和近海索诺拉陆架：（1）通过详细的构造测绘和古地磁分析记录右旋剪切的分布； (2) 利用结构重建、夹层火山岩的 40Ar/39Ar 测年以及同构造沉积盆地和火山盆地的沉降分析来量化转张应变率； (3)通过对近海Tiburon盆地现有的多道地震数据的解释，将陆上地质记录与近海构造和盆地整合起来。加利福尼亚湾为研究大陆裂解过程提供了一个极好的天然实验室。先前的研究表明，温暖的大陆地壳往往会抵抗局部变形，这是大陆岩石圈破裂所必需的。这项研究的数据将加深对北美西部温暖地壳如何以及为何破裂形成加利福尼亚湾的理解，加利福尼亚湾自大约 600 万年前就开始开放。该项目得到了 EAR 构造计划、NSF 国际科学与工程办公室和 NSF/OCE MARGINS 计划的支持。 该研究涉及研究生和本科生的大量参与、与美洲原住民的合作以及与墨西哥研究机构的强有力的国际合作伙伴关系。