Marginal rift system along late Jurassic, conjugate margins of the Gulf of Mexico: Rift continuity, age, and tectonic significance

Abstract

The marginal rift system (MRS) is a long-recognized, linear, generally salt-filled feature that is adjacent to Late Jurassic, oceanic crust underlying the deep, central Gulf of Mexico (GOM). We have studied the MRS on both conjugate margins of the GOM using a combination of gravity, magnetic and seismic reflection data. On the northern (U.S.) conjugate margin, the MRS can be mapped as a continuous rift feature over a distance of 378 km from the west-central Florida margin to a point where it disappears beneath the Louann Salt canopy near Mississippi canyon. As seen on both potential fields and seismic reflection data, the MRS progressively widens from west to east with an average width of 25 km along the Florida margin to a greater width of 50 km to its western point in the northern GOM. Although imaging the base of the MRS is problematic due to the presence of salt, the depth of the MRS deepens from west to east with an average 1 km depth along the Florida margin to an average depth of 4 km at its western limit. On the southern (Mexican) conjugate margin, the MRS can be mapped as a continuous feature for a distance of 678 km from the eastern Yucatan margin to a point where it disappears beneath the Campeche salt province. As seen on both potential fields and seismic reflection data, the MRS progressively widens from east to west from an average width of 25 km along the Yucatan margin to a greater width of 55 km to its western point in Campeche. The observed depth of the MRS varies from 1 km along the Yucatan margin to 9 km at its western point. Plate restorations using oceanic fracture zones realign the eastern endpoints of the MRS on both conjugate margins within an error of 40 km. The disappearance of the MRS in west-central Florida and eastern Yucatan reflects minimal extension and necking of the continental crust near the GOM pole of opening.

AAPG Datapages/Search and Discovery Article #90369 © 2020 AAPG Hedberg Conference, Geology and Hydrocarbon Potential of the Circum-Gulf of Mexico Pre-salt Section, Mexico City, Mexico, February 4-6, 2020