The Structure and Evolution of the Northern Gulf of Mexico: A View from Laurentia

Considering the natural resources present along the north margin of the Gulf of Mexico, our knowledge of the region's deep structure and evolution is surprisingly modest. Both on land and out to the Sigsbee scarp, existing deep seismic results are either lacking or are of relatively low resolution. In order to fully understand the history of the Gulf of Mexico, we must understand the structural framework that was created by the break-up of Rodinia in the Neoproterozoic/Cambrian, the Ouachita orogeny, and the early phase of Mesozoic rifting inland that was essentially unsuccessful. Existing data when subjected to a fully integrated analysis, does provide a general picture the structural framework, but many questions about the southern extent of Laurentian lithosphere, the nature of the Laurentian margin, the nature of the structural blocks that lie outboard of the Ouachita margin, the nature of the Ouachita orogeny, and the evolution of the lithosphere under the Gulf Coast region remain unanswered. Thanks to refraction data recorded in southern Missouri, COCORP deep reflection profiles in Arkansas, the first PASSCAL wide-angle reflection/refraction experiment in southern Arkansas and northern Louisiana, and an on-shore/off-shore experiment along the Texas-Louisiana border, our best constrained integrated model shows that an relatively abrupt and largely intact passive margin developed after the break-up of Rodinia. This model and the geologic evidence along the Ouachita orogen suggest that this tectonic event involved a soft collision. Then, Triassic extension formed a failed rift in southern Arkansas, and then southern edge continental crust of unknown origin formed in the vicinity of the coastline near the Texas-Louisiana border.