Abstract The broad, shallow banks and intervening deep water (800-4000 m) channels of the Bahama Platform are unlike any other topography on the larger Atlantic margin (Fig. 1). The Bahama Platform covers roughly an area of 470,000 km2, which is nearly equivalent to the area of the exposed Atlantic coastal plain from Cape Hatteras to Florida. The Bahama Platform is divided into a northwest part and a southeast part by a northeast trending line between Rum Cay bank and Oriente, Cuba (Fig. 1). The northwest part of the Platform is characterized by a larger portion of the area being shallow banks and a lesser portion being deep-water channels and basins with water depths of 800-4000 m. In contrast, the southeast portion of the Platform has a greater portion of the area as deep water channels surrounding smaller isolated banks; the depths of the channels are generally deeper than 2000 m. (Uchupi and others, 1971). The deep channels and basins segmenting the Bahama Platform are of three different types: 1. open seaways with openings to deeper water at both ends; 2. closed seaways of linear proportions but open to deeper water only at one end; and 3. circular and semi-circular basins. Examples of open seaways are the Florida Straits, the Santaren/Nicholas Channels, the Northwest Providence Channel, the Northeast Providence Channel, and the Old Bahama Channel; Tongue of the Ocean (TOTO) and Exuma Sound are closed seaways; and Columbus Basin and Caicos Basin are semi-circular types.

Abstract Recently obtained high-energy multichannel seismic reflection profiles across the Blake Escarpment show that the oceanic basement, identified as a hyperbolic reflector, forms a deep sediment-filled trough at the base of the escarpment. The western boundary of the trough is formed by a steep rise (45°-60°) of acoustic basement producing an apparent structural relief of more than 2.5 sec for the trough. Seismic velocities were determined as 3.23 to 3.95 km/sec and indicate 4.03 to 4.94 km of sediments in the trough, which deepens to approximately 11 to 12 km. The steep west side suggests fault control and deposition in a fault-bounded half-graben trough. Undisturbed sediments lie over Horizon β which passes across the trough without deflection on one profile, and which is the shallowest disturbed and upturned reflector on another profile. Correlation of reflectors involved in the structure of the trough with the nearby DSDP Site 391 indicates that the deeper seismic layers include sediments older than Late Jurassic. These old sediments filling the fault-bounded trough at the base of the Blake Escarpment should include facies deposited during the earliest opening of the Atlantic, perhaps in the Early Jurassic. The seismic reflection profiles also show reflectors at the edge of the Blake Plateau which can be correlated with DSDP Drill Site 390. Important reflectors of earliest Eocene, Campanian/Albian and Barremian age can be traced westward to depths of 3.4 km (2.8 sec) under the Blake Plateau. Hyperbolic reflectors, not associated with igneous basement, occurring over acoustically opaque zones are interpreted to be well-cemented, high-velocity carbonate bank-margin complexes as drilled at DSDP Site 392.