Gulf of MexicoBasin formationTectonic reconstructionMagma-richMagma-poorSeafloor spreadingMOJAVE-SONORA MEGASHEARIBERIA ABYSSAL-PLAINU-PB AGESSEISMIC-REFRACTION MEASUREMENTSCONTINENT-OCEAN TRANSITIONSOUTHEASTERN UNITED-STATESSEA-DRILLING-PROJECTPOOR RIFTED MARGINSPERDIDO FOLD BELTCRUSTAL STRUCTURE