Seismic reflection profiles along the drill holes on the continental margin off Florida

Abstract

Abstract : Continuous seismic reflection profiles along the line of JOIDES drill holes were adjusted for the velocity of sound at depth, as measured in one of the drill holes and determined at nearby seismic refraction stations. The adjusted reflecting horizons agree in many respects with the stratigraphic section which includes strata of Miocene, Oligocene, Eocene, and Paleocene age, as indicated by samples from the drill holes. The reflection profiles provide continuity of data between the drill holes and extend to much greater depths than the drill; thus they supplement and amplify information derived from the drill samples. Both kinds of data show that the continental shelf is underlain by a Tertiary sequence that has prograded seaward so that the foreset beds form the past and present Florida-Hatteras Slope. No evidence of faulting at the Florida-Hatteras Slope is exhibited by the reflecting horizons. A shallow ridge (or anticline), probably of Cretaceous strata, may underlie the middle part of the continental shelf. The seismic profile between two drill holes on the Blake Plateau contains reflecting horizons that correspond fairly well to the tops of Oligocene and Paleocene strata that were sampled by the drill. These strata continue beyond the plateau, and they partly mantle the Blake Escarpment. Deeper reflecting horizons lie within the Cretaceous sequence, and some may even be older than Cretaceous; they are truncated by the Tertiary beds that mantle the Blake Escarpment. (Author)