Post-rift Magmatism at Passive Margins: An Integrated Study of the Northern Gulf of Mexico Basin

The pre-Cenozoic tectonic history of the Gulf of Mexico (GoM) can be broadly described as Triassic rifting, followed by Jurassic seafloor spreading and post-rift igneous activity as well as domal uplifts and rapid subsidence during the Late Cretaceous. Igneous rocks, identified from geophysical data and outcrops, extend from the Uvalde and Balcones volcanic fields in Texas, through northern Louisiana and eastern Arkansas, to the Jackson Dome in Mississippi. How this widespread magmatic event affected the thermal and structural framework of the crust and the sedimentary system in the northern GoM basin, remain poorly understood.

Competing hypotheses exist regarding post-rift igneous activity: 1) Magmatism in the northeastern GoM basin is part of the Bermuda hotspot track; 2) The subduction of the Farallon plate caused distant lithospheric flexure and associated igneous activity in the northwestern GoM basin; 3) Edge-driven mantle convection produced melts at the continent-ocean boundary; 4) Grenville and Ouachita sutures led to opportunistic igneous activity.

Preliminary results show that, instead of an eastward age progressive track, which is predicted by the Bermuda hotspot hypothesis, the spatial distribution and ages of igneous rocks follow the transition between continental and oceanic crust; it also roughly coincides with the Grenville and Ouachita sutures. It is also possible that the shallow-angle subduction of the Farallon plate could trigger magmatism ca. 1500 km from the trench; a modern analog is the subduction of the west Pacific plate and the Changbai volcano in northeast Asia. Here we emphasize the tectonomagmatic evolution of the northern GoM basin; and moreover suggest post-rift magmatism at passive continental margins is likely affected by both edge-driven convection and inherited lithospheric structures.