CORDILLERAN TECTONIC IMPLICATIONS OF THE TRIPLE JUNCTION MODEL FOR THE GULF OF MEXICO ORIGIN

The Gulf of Mexico origin, based on the Triple Junction Model, was initially proposed in 1993; later in the GSA Annual Meeting at El Paso, in 1997. It is based on redbeds and salt palynostratigraphy data obtained from Mexican Oil Basins, since 1975.

The initial RRR triple junction system was formed during Late Liassic near NE Tampico by the SE-NW Texas-Boquillas-Sabinas, the SW-NE Campeche Escarpement and the N-S Nautla-Pico de Orizaba arms, where the Texas-Louisiana, Western Region of Mexico, and Chiapas-Yucatán subplates came together. Because the last one was joined to South American plate, it was stable during Jurassic, and only Texas-Louisiana and Western Region of Mexico subplates were displaced northwestward, the first one faster than the second one; the Texas-Boquillas-Sabinas arm became a megashear zone, parallel to the southern Chihuahua-Sabinas graben. So, the original RRR triple armed graben formed two masses with a predominantly ridge boundary, and a failed arm of a ridge forming a trough. This displacement was possible, due to the formation of the NW-SE Pico de Orizaba-Laguna Superior megashear, and to the reactivation of the NW-SE Vancouver-Bahamas megashear; and because a subduction zone existed in the Pacific border of the North-American Plate. This motion allowed the Campeche Escarpement and Nautla-Pico de Orizaba arms became wider ridges and seafloor spreading zones, where the Gulf of Mexico formed.

The northwestward motion of the Texas-Louisiana subplate, bordered by the Texas-Boquillas-Sabinas and Vancouver-Bahamas megashears, at present in Canada and Mexico frontiers, originated the 800 km displacement of the Ouachita System and it is related to tectonic phenomena in the Pacific subduction region, as a very active compressive zone during Jurassic-Eocene time (main Cordilleran orogeny). Possible related phenomena are: a) Basin and Range Province width is maximum in USA area and narrower near the megashears; b) Central Rocky Mountains show fold and thrust belt, basins and basement uplifts in foreland region; c) distribution of preorogenic (Early-middle Jurassic), synorogenic (Late Jurassic), and postorogenic (Middle-late Cretaceous) granitic batholiths of Sierra Nevada; d) existence and distribution of principal “suspect terranes”, and e) major tectonic and economic features of Cordillera.