Unzipping the Gulf of California

In the Gulf of California, continental rupture occurred as the Baja California peninsula was transferred from the North American plate to the Pacific plate. While the ~6 Ma rupture of the continent and the capture of Baja California by the Pacific plate is well known, the nature of crustal deformation that led up to this event is poorly understood. A better understanding of the tectonic conditions that precede continental rupture is essential for refining models of plate tectonics.

Tom Peryam is studying strata in late Miocene (~12-6 Ma) sedimentary basins in coastal Sonora and Isla Tiburon, Mexico, in order to test two competing models for the tectonic evolution of the Gulf of California (see figure below). He is investigating the crustal deformation that preceded rupture along the present-day Gulf of California. Knowledge of the tectonic history of this region is gained by measuring stratigraphic and volcanic sections, measuring paleocurrent directions of ancient streams, mapping the distribution and thickness variations of sedimentary deposits, and determining the source of basin strata. Tom will use this basin analysis to link basin deposits to specific faults. This study will allow him to determine the timing of activity on faults which existed prior to the opening of the Gulf of California, and thus to understand the tectonic forces which were at work in the region.