New Insights into the Mesozoic Evolution of the Gulf of Mexico Basin from Gravity and Deep-Penetration Seismic Reflection Data

摘要

I review opening models for the Gulf of Mexico (GOM) in light of our own studies of deep-penetration seismic reflection data in the eastern GOM. Most groups agree that the first phase of syn-rift GOM opening is late Triassic to early Jurassic (235 to 174 Ma) in age, northwest to southeast in extension direction, and responsible for creating a broad zone of thinned, continental crust along the northern margin of the GOM and underlying the northern salt basins of Texas, Louisiana, and Mississippi. This Late Triassic to early Jurassic rift zone is an along-strike continuation of Triassic rifts present along the eastern margin of North America. However, in the northern GOM case the rift failed to culminate in production of a parallel and contiguous zone of oceanic crust across the broad northern GOM. Progress has been slow in understanding the early history and crustal structure of this area in the GOM, due to the obscuring presence of an overlying sag basin of post-early Jurassic age filled by 3-4 km of depositional salt (now remobilized). The second and much better understood phase of GOM opening, is late Jurassic (156 to 145 Ma) and post-salt in age, and formed a large expanse of salt-free, Jurassic oceanic crust underlying the deepwater GOM shared by the U.S., Mexico, and Cuba. This second late Jurassic opening phase occurred along a highly arcuate slow spreading ridge, now well imaged on basin-wide satellite gravity maps. We have georeferenced our grid of deep-penetration seismic and well data in the eastern GOM, along with recent refraction studies to both ground-truth these satellite images and provide details of the early breakup and separation. Our eastern and northeastern GOM continent-oceanic boundary, defined by deep seismic profiles is within 20 km of that inferred from satellite gravity. We have used the shape of the satellite-imaged fracture zones in the Mexican GOM to improve the pole position for this second phase of GOM opening, which is located in the Straits of Florida. This pole restores trends of crustal fabric in Florida and the Yucatan Peninsula seen on gravity and magnetic maps to pre-rotation parallelism. We use this pole to create a kinematic plate model for the second phase of GOM opening that respects all available seismic reflection, refraction, well, and satellite imagery.