Monday, 6 October 2008: 8:25 AM
George R. Brown Convention Center, 332CF
A series of paleotectonic and paleogeographic time slices at 10 m. y. intervals are constructed to portray a geodynamic Cretaceous history of western North America. The resulting model tracks terranes while complex and controversial Mesozoic tectonic events unfold. The geodynamic model is based on several premises and models that are linked chronologically to orchestrate the geologic history of the region: 1) The Jurassic-Cretaceous Cordilleran arc was built on the Stikine, Quesnell, Klamath, and related terranes and SW cratonic North America and formed a contiguous arc - trench complex. 2) A series of fringing arcs lay outboard. 3) The exotic Wrangell terrane collided with the outboard terranes and amalgamated with some to form the Baja BC plate. The Baja BC plate then collided with the North American plate at the latitude of northern(?) California in the Early Cretaceous. 4) We follow the moderate Baja BC model in which it translated southward along the Pacific margin to where its southern margin was at the latitude of the southern Sierra Nevada & central Arizona ~85 Ma. 5) The Late Cretaceous segmentation and shallow subduction of the narrow Laramide slab beneath the Salinia-Mojave terranes immediately south of Baja BC created extensive underthrusting and metamorphism inboard of the coast and generated the Laramide orogeny on the craton. 6) Post-85 Ma, Baja BC transformed northward possibly contributing to transpressional effects along Sierra-Klamath terranes and generated the northern Laramide belt. The major events elucidated above may tie eastward into major Western Interior seaway transgressive-regressive events as follows: 1) Baja BC – North American collision coupled with southward oblique covergence generated the early Sevier orogeny and widespread post-Morrison unconformities across the SW Colorado Plateau; 2) ensuing compression generated Cretaceous foreland basin and Cenomanian-Turonian transgression; 3) shallow slab subduction and northward Baja BC transpression generated Late Campanian-Maastrichtian regression.