Bahamas Salient of North America: Tectonic Framework, Stratigraphy, and Petroleum Potential: ABSTRACT

Abstract

Radiometric dates from the sialic, continental, Florida basement demonstrate a minimum range in age for that basement of early Paleozoic-late Proterozoic. Geophysical data--seismic, gravimetric, and magnetic--suggest that this continental crust extends unbroken from Florida to the eastern Bahamas and northern Cuba. The total area involved, 300,000 sq km (116,000 sq mi), overlaps Africa in accepted "predrift" reconstructions. This overlap extends more than 1,500 km (960 mi) in an east-west direction. Because of this and the probable great age of the continental crust beneath the Bahamas, accepted "predrift" reconstructions are unacceptable, and alternate explanations ranging from the Nafe-Drake drift model to a fixist model must be reconsidered. The sialic crust of the Bahamas has played an important role in the geologic development of the Cuba-Bahamas-Florida region. (1) A pre-Jurassic basement ridge in central Cuba--extending to the longitude of the eastern Bahamas--played a major role in localizing the salt deposits of the Early and Middle Jurassic Punta Alegre Formation. This ridge extended much of the length of Cuba and apparently was a critical barrier for the salt basin. (2) The Early to Middle Jurassic San Cayetano Group of western, south-central, and possibly southeastern Cuba was derived from a sialic terrane--presumably in Florida, Cuba, and Yucatan. (3) The southern and eastern margins of this continental salient, in Cuba and north of the Dominican Republic, determined the location of the western half of the Late urassic-middle Eocene Greater Antilles orthogeosyncline; the eugeosyncline borders the oceanic-continental crust boundary, whereas the miogeosyncline and associated basins overlie the continental crust beneath northern Cuba and the southern Bahamas. Since the beginning of Early to Middle Jurassic time, Cuba, the Bahamas, and south Florida have subsided 10-11 km. Extensive carbonate and evaporite deposition characterized northern Cuba, all of the Bahamas, and southern Florida for approximately 200 m.y. Although the gross lithologies would suggest the persistence of uniform depositional conditions with few facies changes, lateral and vertical facies changes in the carbonate-evaporite sequence are extensive. Thrusting from the Caribbean Sea during Late Jurassic (or earlier) through middle Eocene time produced large, gentle structures on the site of the present Bahamas which behaved as a foreland platform during the development of the Greater Antilles orthogeosyncline. Adequate reservoir and source rocks, seals, structures, and possi ilities for large stratigraphic traps exist in the Mesozoic and early Tertiary section from northern Cuba to southern Florida, and from the Gulf of Mexico to north of Hispaniola. One of the most attractive prospective areas is the Little Bahama Bank.