Constraints on the tectonic development of the eastern Gulf of Mexico provided by magnetic anomaly data

Abstract

Boundaries between oceanic and transitional crust in the eastern Gulf of Mexico have been delineated using detailed, accurately navigated, high‐quality aeromagnetic data. These data indicate that considerably more oceanic crust may be present than previously suggested by other geophysical data, especially seismic reflection data. The N‐S extent of oceanic crust substantially increases westward from approximately 280 km near 87°W to roughly 390 km near 90°W, indicating the proximity (<10°) of the pole of rotation. Variations in the amount of oceanic crust together with discontinuities in the magnetic anomaly patterns, interpreted as the traces of fossil transform faults or fracture zones, have been used to obtain a rough estimate of the location of the pole of rotation (24°N, 81.5°W) for the seafloor spreading phase of opening. The magnetic data have been used to develop a model for the opening of the Gulf and to identify some geometrical relationships between its conjugate continental margins. Based upon the estimated pole position, the eastern Gulf is interpreted to have opened in an approximately NNE‐SSW direction with the counterclockwise rotation of Yucatan away from North America. The seafloor spreading phase of movement accounts for about 25° of the counterclockwise motion of Yucatan. Rotating the Yucatan block clockwise by this amount to restore it to its predrift position places the Campeche Bank adjacent to the Mississippi Trough‐Louisiana shelf. Further clockwise rotation of Yucatan by an additional 30–35° about this pole restores extended crust to its original thickness and is consistent with rotations of Yucatan predicted from paleomagnetic data from Chiapas.