Alleghenian reconstruction and subsequent evolution of the Gulf of Mexico, Bahamas, and Proto‐Caribbean

Abstract

A detailed model for the evolution of the Gulf of Mexico, the Bahamas and the Proto‐Caribbean is built within the framework provided by a detailed initial Alleghenian (western Pangean) reconstruction and an accurate subsequent relative‐motion history between North America and Gondwana (northern Africa and South America). The Alleghenian reconstruction closes all pre‐Jurassic oceans; accounts for Jurassic attenuation of continental crust by restoring that attenuation to original prerift continental thicknesses; incorporates an improved Equatorial Atlantic fit between northern Brazil and the Guinea margin of Africa; quantitatively removes changes in shape of northern South America due to Late Cretaceous and Cenozoic accretion and internal deformation; includes pre‐Mesozoic continental crust presently underlying the western Bahamas and southern Florida; and correlates Late Paleozoic geology of Yucatan with its neighboring continental masses. Extension occurred within the Gulf of Mexico from Late Triassic to earliest Cretaceous time, but seafloor spreading was delayed until the Late Callovian. This divided a single Gulf‐wide salt basin into the Louann and Campeche salt provinces. The Yucatan block progressively rotated about 43 degrees counterclockwise away from the Texas‐Louisiana margin around a pole in northern Florida. The Tamaulipas‐Golden Lane‐Chiapas fault zone of eastern Mexico is interpreted as the remains of an initially intracontinental transform system along which Yucatan migrated. Attenuated continental crust beneath southern Florida and the western Bahamas, termed here the Florida Straits block, migrated approximately 300 km out of the eastern Gulf, approximately along Central Atlantic flow lines. These rotations are consistent with recently suggested magnetic anomaly trends in the Gulf of Mexico (Shepherd et al., 1982; S. Hall, personal communication, 1984). The Proto‐Caribbean formed synchronously by a fan‐like rotation of Yucatan away from Venezuela.