Gulf of Mexico tectonic history: Hotspot tracks, crustal boundaries, and early salt distribution

A Late Jurassic mantle plume may have generated hotspot tracks on the North American plate and the Yucatan Penninsula tectonic block as the Gulf of Mexico opened (ca. 150 Ma). The tracks are identified from deep basement structural highs that have been mapped by integrating seismic refraction and gravity data. They are associated with high-amplitude, distinctive gravity anomalies that provide the basis for a kinematic reconstruction that restores the western ends of the hotspot tracks with a 20° clockwise rotation of the Yucatan block or almost one-half the total rotation required to open the Gulf of Mexico Basin. The duration of track generation is estimated to have been about 8–10 m.y. or almost one-half the total time required to open the Gulf of Mexico Basin. Prior to this rotation, extension of continental crust over a 10–12-m.y. interval was the result of approximately 22° of counterclockwise rotation and crustal thinning. Autochthonous salt appears to be confined to the continental flanks of the hotspot tracks, confirming that salt was deposited during continental extension and not after ocean floor had begun to form. A prominent gravity anomaly along the western boundary of the basin is interpreted to be produced by a marginal ridge, which was created along the ocean-continent transform boundary as the basin opened. The eastern flank of this marginal ridge and the northernmost, easternmost, and southernmost terminations of the hotspot tracks are interpreted to coincide with the oceanic-continental crustal boundary in the basin. Dale E. Bird consults in the oil- and gas-exploration industry as a potential fields specialist. Since 1981, his experience in the industry includes acquisition, processing, interpreting, and marketing geophysical data, including positions with Aerodat, World Geoscience, Marathon Oil Company, Digicon, and Aero Service. He earned a Ph.D. from the University of Houston in 2004, and his research interests are regional geology and tectonics and the integration and interpretation of gravity and magnetic data. He is a member of several local and international geological and geophysical societies.Kevin Burke has been a professor of geology in the University of Houston since 1983, having previously lived and worked in several parts of the world. His main research is in tectonics: The large-scale evolution of planetary lithospheres. His current interests include African and Asian geology and the derivation of large igneous provinces from the core-mantle boundary. Stuart A. Hall is a professor of geosciences specializing in the study of gravity and magnetic fields. He received a B.Sc.(honors) degree in physics from the University of Birmingham, United Kingdom (1968) and a Ph.D. in geophysics from the University of Newcastle-upon-Tyne, United Kingdom (1976). His current research interests are mainly focused on the use of geophysical data to investigate the development of small ocean basins and orogenic belts. He is a member of the Society of Exploration Geophysicists, American Geophysical Union, Royal Astronomical Society, and Sigma Xi Research Society. John F. Casey is a professor of geology and chair of the Department of Geosciences at the University of Houston specializing in structure, tectonics, and geochemisty. He received a B.A. degree in geology from the University of Pennsylvania in 1975 and a Ph.D. in geology with honors from the State University of New York, Albany, in 1980. His research has focused on the tectonics and geochemistry of midocean ridges, transform faults, and ophiolite-bearing orogenic belts.