Jurassic tectonics of the Gulf of Mexico and central Atlantic Ocean

Detailed interpretations of geophysical data have lead to the development of new models for the Jurassic evolution of the Gulf of Mexico and the central Atlantic Ocean.; The Gulf of Mexico ocean basin is essentially surrounded by continental crust, indicating that at least one ocean-continent transform boundary formed as it opened. Three distinctive gravity anomalies are interpreted to be those produced by prominent basement structures that also formed as the basin opened. Two of these structures are hotspot tracks formed during a 20° counterclockwise rotation of the Yucatan block. The third is a north-south marginal ridge along the western side of the basin that indicates the presence of a shear margin. The rotation, and hotspot track lengths considered as a function of time, account for about one-half of the total rotation and time required to form the basin (∼10 My). Rotations prior to this involved continental extension and accompanying salt deposition. As such the basement structures appear to define the oceanic-continental crustal boundary and the approximate seaward limits of autochthonous salt deposition.; In the central Atlantic Ocean, M-Series seafloor spreading magnetic anomalies have been used to develop a kinematic reconstruction of the region. These data indicate that two seafloor spreading ridge jumps during the Jurassic were followed by a period of asymmetric seafloor spreading. The earliest ridge jump was towards the east and occurred about 170 Ma, leaving part of African lithosphere between the East Coast Magnetic Anomaly and Blake Spur Magnetic Anomaly. The second ridge jump was towards the west and occurred between 164 Ma and 159 Ma. Estimated half-spreading rates for the North American and African flanks of the central Atlantic between 154 Ma and 120.6 Ma are 14.4 mm/a and 12.9 mm/a respectively.