Permian and Triassic paleomagnetism from Mexico and the southwestern United States: Implications for the evolution of the Gulf of Mexico and the magnetic polarity time scale.

We present paleomagnetic data for the Late Permian Dewey Lake Formation (northwest Texas), the Triassic section of central New Mexico (Moenkopi and Chinle formations), and the Chiapas massif of southern Mexico (Late Permian). The paleogeographic and tectonic implications of the results are discussed in the context of the models proposed for the rotation of the Maya Block and the opening of the Gulf of Mexico. The paleomagnetic record from Chiapas strongly favors those models which indicate anticlockwise rotation of the Maya Block as the mechanism for the opening of the Gulf. The results are also consistent with a pre-rift configuration in which this block is located in the present area of the Gulf off the coast of Texas and Louisiana. The paleomagnetic record from the southwestern United States confirms the general reliability of previous Permian and Triassic results in the southwest US and constrains the Permo-Triassic segment of the NA reference apparent polar wander path. Data from New Mexico indicate that central New Mexico has experienced a small clockwise rotation with respect to the NA craton similar to that of the Colorado Plateau. The magnetostratigraphy of the Dewey Lake Formation constrains the age of the end of the Kiaman Superchron ($\sim$256 Ma). A preliminary Triassic magnetostratigraphic time scale is presented by incorporating data from this study, a revised correlation of the Triassic section of the southwestern US, and recently published data from China, Spain, and the northeastern US.PhDGeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105414/1/9124065.pdfDescription of 9124065.pdf : Restricted to UM users only