OPENING OF THE GULF OF MEXICO: A RESULT OF MAJOR PLATE MOTION

Our study of the Gulf of Mexico [GOM] started with a revised fit between North America [NOAM] and West Africa. Prominent bends in the East Coast Magnetic anomaly of NOAM and the West African Coast Magnetic anomaly are used for the prerift position of the two continents. That fit, together with the known fit between Africa and South America [SOAM] leaves a very small box in which to fit a rotated paleo-Yucatan Peninsula. Timing and motion of eastern Mexican terranes were used to further constrain the early opening of the GOM. Rotation of the Yucatan block with respect to North America was influenced by the motion between South America and North America.

The earliest rifting in the Central Atlantic did not continue south of the Great Bahama Bank. It was transformed to the west across Florida, resulting in oblique stretching in the region of the future GOM. In our model, the Yucatan block with the Chiapas Massif moved as part of the SOAM block until at least 175 Ma. A true “Mojave-Sonora Megashear” did not reach the GOM and is older than any rifting or stretching in the GOM. A Jurassic left-lateral transform fault existed between the Coahuila Terrane of northeastern Mexico and the Tampico terrane of eastern Mexico. Based on our new reconstructions, the postulated fault had at most 280 km of offset, with the time of the offset being Early to at most Middle Jurassic. The first phase of opening in the GOM, between 195 Ma and 165 Ma, produced stretching and extension but no true ocean crust. This motion produced crustal extension along the present Gulf coast margin of Texas and Louisiana, the probable opening of the Sabinas Basin in northeastern Mexico and left-lateral motion along a postulated Coahuila-Tampico Fault, and at least one transform fault that cut the Florida Peninsula.