Seismic-Profiler Survey of Blake Plateau

Continuous seismic-reflection profiles on the Blake Plateau are correlated with sediment cores, seismic-refraction data, and logs of wells on Florida to study the structural relations of the Florida peninsula and continental shelf with the plateau. Results indicate that the entire Blake-Bahama-Florida area was the site of shallow-water carbonate deposition behind a barrier reef until late in the Mesozoic. Death of the reef along the Blake Plateau margin and continued subsidence of the entire area created the present submerged plateau. Florida and the Bahama banks continued to build throughout the Tertiary and have maintained an elevation near sea-level. Four strong reflectors are observed in the plateau sediments, the deepest apparently representing an interface within the Upper Cretaceous and correlating with the top of a 4.5 km./sec. refracting layer. The overlying beds probably are composed of bank-derived calcarenite and calcilutite; the reflectors correspond to major changes in sediment types or rates of deposition. The Tertiary sediments on the plateau essentially form a wedge, about 1,200 m. thick on the west side and 200-300 m. thick near the escarpment on the east. The extension of the Cape Fear arch southward onto the plateau apparently diverts and restricts the flow of the Gulf Stream. This has resulted in extensive erosion of much of the surface of the plateau. In places the erosion has uncovered beds of Eocene and Paleocene age. The material eroded from the plateau by the stream, as well as that which stayed in suspension, has b een swept off the plateau and has formed the Blake-Bahama outer ridge.