Deep Cenezoic Sediments in Front of the Barbados Ridge Complex, Odp Site 672: Hemipelagites, Turbidites, and Possible Contourites in Western Central Atlantic Ocean

Abstract

The cenozoic sediments cover of western central Atlantic oceanic floor was cored at about 5 000 m depth, close to the deformation front of the Barbados Accretionary Prism. Good preservation of sedimentary structures and high recovery rate allowed the recognition and study of hemipelagic calcareous or siliceous clays and muds, with or without interbedded airfall volcanic ash beds, and with or without interbedded coarser deposits coming from lateral inputs. The latters are either calcareous fine-grained turbidites coming from local shallower oceanic areas, or terrigenous and calcareous (more hypothetical) contourites (reworking turbidites) related to bottom currents running along the South-America margin. Fluid-escape veinstructures, related to dewatering process - upward, vertical to almost horizontal advection - were identified, especially in relation with the beginning of offscraping stress in early Miocene incipient decollementhorizon. Twenty-four color print photos of splitted cores are presented; the macroscopic features they show are commented and discussed.