Reconstructing northern Cordilleran terranes along known Cretaceous and Cenozoic strike-slip faults: Implications for the Baja British Columbia hypothesis and other models

We present a new reconstruction of the mid-Cretaceous (100 Ma) paleogeography of the United States and Canadian Cordillera, based on (a) restoring displacements within the major Late Cretaceous to Cenozoic contractional and extensional belts, and (b) restoring displacements along the major Late Cretaceous to Cenozoic dextral strike-slip faults of the northern Cordillera. The reconstruction moves the southern end of Insular superterrane to the latitude of the southern Klamath Mountains, the southwest Intermontane superterrane to central Oregon, and the southern Coast orogen into the intervening region. Restored terranes partly fill in the region of the Columbia embayment. Total displacements range from ~450 to 900 km, and increase from east to west. These values are smaller than those determined by paleomagnetic studies (1100–3000 ± 500–900 km), but they indicate that discrepancies between geologic and paleomagnetic data sets are not as large as is often assumed. The reconstruction results in the juxtaposition of geologic features that have previously been correlated or that have a high probability of having evolved together. Collectively, these relations lend strong support to the reconstruction, which we call the minimum fault-offset model. The model has important 277 Reconstructing northern Cordilleran terranes along known Cretaceous and Cenozoic strike-slip faults: Implications for the Baja British Columbia hypothesis and other models