Tectonic processes during oblique collision: Insights from the St. Elias orogen, northern North American Cordillera

摘要: [1] Oblique convergence in the St. Elias orogen of southern Alaska and northwestern Canada has constructed world's highest coastal mountain range is principal driver constructing all high topography northern North America. The originated when Yakutat terrane was excised from Cordilleran margin transported along margin-parallel strike-slip faults into subduction-transform transition at eastern end Aleutian trench. We examine last 3 m.y. this collision through an analysis Euler poles for motion microplate with respect to America Pacific. This indicates a Yakutat-Pacific pole near present triple junction predicts dextral-oblique across offshore Transition fault, onland structures adjacent foreland, or both, plate speeds increasing 10 30 mm/yr southeast northwest. Reconstructions based on these show that NNW transport collided block NE trending subduction zone forced contraction EW line elements as driven transition. suggests constricted it Constriction provides explanation observed vertical axis refolding both earlier formed fold-thrust systems collisional suture top stack. also suggest partially accommodated by lateral extrusion western portion toward Important questions remain regarding which parts motion. fault may have much basis our previous interpretations GPS-based geodetic data. Nonetheless, locally overlapped up 800 m undeformed sediment, yet elsewhere shows evidence young deformation. contradiction could be produced if overlapping sediments are too accumulated significant deformation, GPS motions deflected transient strains poorly understood interactions. In either case, more data needed resolve paradox.