2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 3
Presentation Time: 8:45 AM

Opening of the Gulf of Mexico and Motion of the Terranes of Mexico

LAWVER, Lawrence A., GAHAGAN, Lisa M. and NORTON, Ian O., Institute for Geophysics, University of Texas at Austin, 10100 Burnet Rd., Bldg. 196, J. J. Pickle Research Campus, Austin, TX 78758-4445, lawver@ig.utexas.edu

This 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 were 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.

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.