Sedimentary Response to Oblique Convergence: Cretaceous, Tyaughton-Methow Basin, British Columbia

这项研究将检验关于不列颠哥伦比亚省西南部泰奥顿-梅托盆地晚白垩世早期沉积和沉降的三种假说。这些假说将该盆地解释为：1)反映走滑构造作用的拉分作用；2)向盆逆冲断层导致的挠曲盆地；或3)盆地下冲断带上的背靠式盆地。PI还将讨论沉积作用是否发生在弧后与弧前环境中，以及是否发生在可能远至白垩纪墨西哥北部的古纬度。这一结果将约束北美科迪勒拉白垩纪中期的运动学模型以及移动的复合异地地体内部变形的时间和样式。将采用的盆地分析方法包括确定沉积物扩散系统的类型和方向，确定三维相结构，确定沉积物源区的变化组成和位置，确定盆地几何的时间和空间变化，以及确定任何同沉积盆地内构造变形。此外，原始火山碎屑层和火山岩地层的40Ar/39Ar测年将提供准确、可靠的年龄，这对约束古地理、岩石地层和古地磁数据至关重要。一项正在进行的古地磁研究，以确定晚白垩世早期的泰奥顿-梅托盆地及其下伏的异地基底的古纬度。这项研究将有助于揭开北美西部边缘地区增长的历史。

This study will test three hypotheses concerning early Late Cretaceous sedimentation and subsidence in the Tyaughton-Methow Basin, southwestern British Columbia. These hypotheses explain the basin as: 1) a pull-apart reflecting strike-slip tectonism; 2) a flexural basin due to basin-ward thrust faulting; or 3) a piggyback basin on sub-basinal thrusts. The PI will also address the question of whether sedimentation occurred in a back-arc versus a forearc setting and at a paleolatitude possibly as far south as Cretaceous northern Mexico. Results will constrain kinematic models for the mid-Cretaceous North American Cordillera and for the timing and style of interal deformation within a moving composite allochthonous terrane. Basin-analysis methods to be employed include determining the style and orientation of sediment dispersal systems, defining three-dimensional facies architecture, defining the changing composition and location of the sediment-source areas, defining temporal and spatial changes in basin geometry, and identifying any syndepositional intrabasinal structural deformation. In addition, 40Ar/39Ar dating of primary volcaniclastic and volcanic strata will provide precise, reliable ages critical to constraining paleogeographic, lithostratigraphic and paleomagnetic data. An ongoing paleomagnetic study to determine the paleolatitude of the early Late Cretaceous Tyaughton-Methow Basin and its underlying allochthonous basement. The research will help unravel the history of the growth of the western margin of North America.