Structure of the Scotia Sea and Falkland Plateau

Abstract

The results of 57 seismic-refraction profiles recorded in the South Atlantic Ocean south of 47°S are used to describe the gross structure of the Scotia Sea basins, the Falkland plateau, and, to a lesser extent, the North Scotia and South Sandwich ridges. The Drake passage and Scotia Sea basins have normal or nearly normal oceanic crust. Their floors are covered by 300–1000 meters of sediment, except in a band in the western part, where the sediment cover is thin and nonuniform. There is direct correspondence between the position of the band of thin sediments and the position of a low oceanic ridge, as defined by morphology, seismic refractions, magnetic lineations, and earthquake epicenters; this correspondence suggests that the band may represent young oceanic crust produced by sea-floor spreading. Scouring or nondeposition due to strong bottom currents may also have reduced accumulation in this band. The Falkland plateau is a southward-tilted continental block capped by a thick wedge-shaped body of sediments, the top-most layers of which continue farther south to form the floor of the adjacent Falkland trough. The section beneath the Falkland trough is similar to a depressed or subsided oceanic crust overlain by 4 km of low-velocity sediments.