EVOLUTIONARY MODEL FOR CONVERGENT MARGINS FACING LARGE OCEAN BASINS -MESOZOIC BAJA-CALIFORNIA, MEXICO

Mesozoic rocks of the Baja California Peninsula form a convergent-marg in complex that is one of the best-preserved and longest-lived converg ent-margin complexes in the world. It shows a three-phase evolutionary trend that we propose is typical of are systems facing large ocean ba sins. The trend progresses from phase 1, highly extensional intraocean ic-are systems, to phase 2, a mildly extensional fringing-are system, to phase 3, a compressional continental-are system. This trend is larg ely due to the progressively decreasing age of lithosphere that is sub ducted. The modern Earth is strongly biased toward long-lived are-tren ch systems, which are compressional, and so evolutionary models for co nvergent margins must be constructed from well-preserved ancient examp les like Baja California.