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

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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.