Universite Europeenne de Bretagne, France

The Barracuda Ridge and the Tiburon Rise, two major oceanic basement ridges, lie at the western end of the diffuse North America-South America Plate boundary zone, where they enter the subduction zone beneath the Lesser Antilles island arc. There is a large degree of uncertainty in the motion between the North American and South American Plates predicted by kinematic models of plate motion for the region of these two ridges during the Cenozoic and Quaternary. From the analysis of new multibeam and seismic reflection profiles acquired in 2007, together with older geophysical and geological data, we provide new information on the geological history of this area, including the timing of the formation of the Barracuda Ridge and Tiburon Rise in their present-day configurations. The timing of the deformation in this region is now much better constrained through the correlation of several key seismic horizons with existing DSDP and ODP holes. The seafloor topography inherited from the process of formation of the crust at the mid-oceanic ridge, was buried by distal turbidites by the end of the Paleogene. Beginning in the middle-late Miocene and then the Pleistocene, the Tiburon Rise and Barracuda Ridge, respectively, were uplifted and acquired their present-day forms and elevation, which is much more recent than previously believed. In the Quaternary, the uplift was accompanied by the deposition of very large mass transport deposits. The causes of uplift and deformation of the ridges have been convergence between the North American and South American Plates and the flexure of these plates as they enter the Lesser Antilles subduction zone, The zone of uplift and deformation migrated northward during the Neogene and Quaternary. Abstract Copyright (2012) Elsevier, B.V.