Continuous seismic-reflection profiles on Blake Plateau, correlated with sediment cores, seismic-refraction data, and logs of wells on Florida, 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 kmps refracting layer. The overlying beds probably are composed of bank-derived calcarenite and calcilutite.