Opening of the Gulf of Mexico and Motion of the Terranes of Mexico
The very earliest seafloor spreading in the Central Atlantic rifted the outer Blake Rise from NOAM to produce the Blake Plateau basin. Since the earliest rifting could not have continued south of the Great Bahama Bank it had to have been transformed to the west across Florida. In our model, the Yucatan block moved as part of the SOAM block until 175 Ma. A true Mojave-Sonora Megashear did not reach the GOM and is older than any rifting or stretching in the GOM. A left-lateral transform fault must have 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 Middle Jurassic. The first phase of opening in the GOM, between 195 Ma and 175 Ma, produced stretching and extension but probably 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 hypothetical faults that cut the Florida Peninsula.