Abstract Extensional tectonics in the Gulf of California region occurred during middle- to early-late Miocene time. One of the best examples is found at Bahía Concepciόn, which is the largest fault-bound bay on the peninsular gulf coast of Baja California. The extensional basin confined to Bahía Concepciόn developed within an accommodation zone related to the late Miocene east-west extension in the broader Gulf of California region. This contribution is focused on the large, central part of the gulf region along the peninsular axis, sometimes referred to as the Baja California Central Domain ( BCCD ). The mainly volcanic Comondú Group is extensively exposed throughout the BCCD , but on a local basis it occurs as huge andesite blocks associated with stratified units that characteristically dip in opposite directions. This is a direct result of a main east-west extensional episode that generated normal faults on the surface and listric detachment faults at depth. Half grabens are the most common result of such extensional episodes in the BCCD . This event has produced subsidence, creating depocenters for mostly nearshore marine basins. The oldest marine sedimentary units present in the BCCD are the late Miocene–early Pliocene Tirabuzón Formation. Less typically, on Peninsula Concepciόn and at Punta San Antonio, a late Miocene extensional episode has resulted in up-thrown granodiorite basement along bounding faults. Extension on the Bahía Concepciόn zone was responsible for development of a half-graben structure first fully flooded in late Pliocene time. The tectono-sedimentary evolution of the adjacent Santa Rosalía and Bahía Concepción areas is recorded by three stratigraphic stages: (1) pre-rift strata represented by the Comondú Group; (2) a syn-rift stage containing syntectonic siliciclastic deposits; and (3) post-rift strata, represented by the late Miocene to Pliocene flat-lying to low-angle marine sedimentary units. The three stratigraphic stages are interpreted from outcrops in this region.

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Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.