The Barbados Ridge Complex: tectonics of a mature forearc system

Abstract

The Barbados Ridge Complex is the wide accretionary sediment pile associated with the Lesser Antilles island arc. Its width is so great (>200 km) that a trench no longer exists on the oceanward side of it. This development is a product of the age of the system (>50 Ma) and the thickness of sediment on the ocean floor (0.8 km in the north, >4 km in the south). The northward decrease in elevation of the sediment pile and the variation in the style of initial deformation at the leading edge of the pile are related to the northward change in sediment thickness and type. The region in which deformation is prevalent has a westward limit just west of the axis of the minimum negative Bouguer gravity anomaly. In the south the axis of this minimum is coincident with the Barbados Ridge (an outer ‘sedimentary arc’). The deformed rocks of the accretionary pile are overlain by later sediments, which show varying degrees of deformation, and often occupy small basins.