TECTONOSTRATIGRAPHIC STAGES IN THE MESOZOIC OPENING AND SUBSIDENCE OF THE GULF OF MEXICO BASED ON DEEP-PENETRATION SEISMIC REFLECTION DATA IN THE SALT-FREE EASTERN PART OF THE BASIN

The eastern and northeastern Gulf of Mexico provide one of the few areas of the Gulf of Mexico continent-ocean boundary that is not obscured by a thick layer of remobilized salt deposits. I used 17,000 km of deep-penetration, long-offset seismic reflection data tied to five oil exploration wells, gravity and magnetic data, and plate reconstructions to propose six major tectonic stages representative for the overall opening of the Gulf of Mexico, including its north-central and southwestern, salt-covered areas: 1) Triassic stage 1 rifting (230-190 Ma) occurred in a southeast direction and thinned the 450 km-wide zone of transitional continental crust in the northern Gulf of Mexico; rift basins filled with red beds of the Eagle Mills Formation (Late Triassic to Earliest Jurassic); it is not clear if the Triassic rifting was continuous with later Jurassic rifting or whether there was an intervening period of no rifting; 2) Late Jurassic stage 2 rifting (174-166 Ma) occurred during 39 degrees of clockwise rotation of the Yucatan block from its position along the NE GOM and eastern Florida based on the re-alignment of pre-rift, Paleozoic trends seen on regional magnetic maps; rifting in the northeastern GOM is accompanied by subaerial lava flows and interbedded sediments up to 6-8 km thick characteristic of a volcanic passive margin; uplifted rift shoulders led to the formation of a breakup unconformity of latest Jurassic age; 3) Late Jurassic stage 3 sag basin (166-163 Ma) occurred immediately before breakup and resulted in more than 4 km of salt deposition that thins in the northeastern GOM to a thickness of 0-0.5 km; salt thickness variations were likely controlled by preexisting rift topography; 4) Late Jurassic stage 4 separation and formation of 6-8-km-thick oceanic crust; fracture zones and arcuate spreading ridges visible on gravity maps of the central GOM constrain a single and stationary pole position for Jurassic opening; seafloor spreading separating salt of the stage 3 sage basin into two salt bodies - one underlying the US Gulf coast, the other underlying the southeastern Mexican margin. Seafloor spreading ended by the earliest Cretaceous (137 Ma); 5) Cretaceous stage 5 passive margin stage and deposition of overlying stratigraphic sections: on the east Florida shelf over 5 km of mixed carbonate and clastic rocks accumulated while terrigenous turbidites and shallow marine carbonate rocks were deposited in the deepwater GOM; these deepwater sections overlie stage 2 rifts; 6) Cenozoic stage 6 sediments influx stage: on the east Florida shelf thin layer of mainly carbonate accumulated while over 10 km of terrigenous turbidites filled the deepwater GOM; these deepwater sections overlie stage 2 rifts basins and the oceanic crust.