A 30 MA RECORD OF SUBDUCTION GEODYNAMICS PRESERVED IN THE JURASSIC GEOLOGY OF WESTERN NORTH AMERICA

Geological data from western North America fulfill the predictions of geodynamic models which reinforce the role of collision in triggering back-arc extension and slab rollback. Here, I present a new hypothesis that during Jurassic time, the collision of volcanic-arc lithosphere from Alaska to Oregon induced subsequent trench retreat and slab rollback from Oregon to Yucatán. The geodynamics of collision-induced slab rollback explains Jurassic deformation, magmatism, and sedimentation along the entire 6,000-km long paleo-subduction zone and large portions of the North American continent, yields a Jurassic piercing- point restoration suggesting ~ 500 kms of Cordilleran “terrane translation”, shows that numerous Cordilleran terranes were part of the evolution of the North American plate margin by no later than ca. 185 Ma, and suggests that subduction zones can be highly dynamic over just 10 Ma. My hypothesis unifies the Jurassic geology of the entire western North American Cordillera under a fundamental set of geodynamic controls over a 30 Ma period and provides a rare example of direct connections between geodynamic modeling results and the geologic record.