The Opening of the Southern Gulf of California
The Gulf of California is a young ocean basin formed by oblique extensional motion between the North American and Pacific plates and is an example of a common class of rifts. We have developed a tectonic history for the southern Gulf based on recently obtained geological and geophysical information along with older observations. We determine rift timing and rates using as constraints the width of the Gulf, magnetic anomaly patterns, the uncentered position of the Rivera Rise within the Gulf, and the time of deposition of the Magdalena Fan. With these constraints, we construct three alternative opening models, each consistent with the available information. We propose that initial rifting of continental crust in the area began approximately 14 Ma, and that the oceanic crust was exposed no later than 8.3 Ma. Finally, we conclude that Baja California has experienced a total of 450 to 600 km of right-lateral translation since 14 Ma. This amount of displacement is greater than that which can be accommodated on the San Andreas fault zone (a term we will use for the San Andreas, San Jacinto, and Elsinore faults in southern Alta California) and must have been carried in part on faults across northern Baja California and in the offshore Continental Borderland.