Shallow seismic stratigraphy and post-Albian geologic history of the northern and central Blake Plateau

Abstract

Interpretation of >4,700 km of high-resolution, seismic-reflection profiles from the northern and central Blake Plateau was used to reconstruct the geologic history of this continental margin sector since Albian time. Beneath the northern Blake Plateau, a basal Albian sequence is overlain by three progradational sequences inferred to be Turonian-Coniacian, Santonian, and Campanian-Maastrichtian in age. Their clinoform patterns and external geometry suggest that these sequences consist of clastic sediment derived from a source to the west. The position of the seaward terminus of these sequences shifted by as much as 50 km during the Late Cretaceous, presumably in response to variations in the input of clastic sediment. To the south, the progradational units grade into thinner, blanketlike deposits interpreted as being deep-water sediments that accumulated in a slowly subsiding basin. By latest Cretaceous time, sediment was introduced to the inshore reaches of this deep-water basin apparently by a powerful, easterly flowing current sweeping through the Suwannee Strait of southern Georgia and northern Florida. Three thin, but mappable, units of Paleocene, Eocene-Oligocene, and post-Oligocene age comprise the Cenozoic section. Drill-hole data indicate that they consist principally of deep-water foraminiferal oozes and limestones. The dominant geologic agent during the Cenozoic was the Gulf Stream, the flow axis of which shifted periodically across the Plateau in response to global sea-level fluctuations. This powerful current influenced the location and development of the Florida-Hatteras Shelf and Slope, controlled facies distribution, and scoured the surface of the Blake Plateau, thereby producing an abbreviated sedimentary section containing numerous unconformities. The persistence of Gulf Stream erosion during the Cenozoic, in conjunction with crustal subsidence, transformed the distal edge of this continental margin sector into a deep-water, sediment-starved environment, the Blake Plateau.