This project will evaluate data in support of the existence of a large island in northernmost Sonora during the Mesozoic. Preliminary data suggests that the island was surrounded by relatively deep marine environments, rather than the shallow marine and fluvial environments postulated by previous workers. The data will delineate the disposition of land masses along the southwestern margin of North America during the Cretaceous. The results will have important tectonic implications for the evolution of southwestern North America.
