From Bureau of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
For more information, please contact the author.

Bureau Seminar, September 7, 2007

Pangea breakup and the early evolution of the Central Atlantic Ocean, assembly of Mexico, and opening of the Gulf of Mexico


Dale Bird

Bird Geophysical, University of Houston

Abstract:

Closing ocean basins, by rotating tectonic plates about Euler poles to corresponding geomagnetic isochrons, is an objective method for analyzing reconstructed continental margins. Reconstructions of the North American, South American and African plates for Chrons M40 (165.1 Ma), M25 (154.1 Ma), and M0 (124.6 Ma), including the accretion of the continental blocks that form Mexico as well as the opening of the Gulf of Mexico over these time frames, reveal critical aspects for understanding the tectonic evolution of the region. Early sea floor spreading in the Central Atlantic included two ridge jumps (ca 170 Ma and ca 160 Ma) that are thought to be related to tectonic plate reorganization, following the breakup of Pangea and initial sea floor spreading in the Central Atlantic (ca 180 Ma), including the opening of the Gulf of Mexico.

The Yucatan-Chiapas block, the Coahuila, Tampico and Del Sur blocks of north and east-central Mexico, and southeastern United States from southern Texas eastward to Florida (south of the Ouachita-Marathon suture) are Gondwanan terranes that were accreted onto Laurentia during Permian time. The Gulf of Mexico ocean basin formed by rifting these contiguous Gondwanan terranes followed by seafloor spreading. Three prominent, deep basement structures in the western Gulf of Mexico are interpreted to be a marginal ridge that formed along a transform fault, and two hotspot tracks formed by a single mantle plume, as the Yucatan-Chiapas block rotated counterclockwise to open the basin. Supporting analogs for this model include mantle plumes that preceded the continental fragmentation of Pangea.