The influence of the highly oblique plate convergence at the northern Lesser Antilles onto the margin strain partitioning and deformation pattern, although frequently invoked, has never been clearly imaged. The Anegada Passage is a set of basins and deep valleys, regularly related to the southern boundary of the Puerto-Rico-Virgin-Islands (PRVI) microplate. Despite the publications of various tectonic models mostly based on bathymetric data, the tectonic origin and deformation of this Passage remains unconstrained in the absence of deep structure imaging.

During cruises Antithesis 1 and 3 (2013 - 2016), we recorded the first deep multichannel seismic images and new multibeam data in the northern Lesser Antilles margin segment in order to shed a new light on the structure and tectonic pattern of the Anegada Passage.

We image the northeastern extent of the Anegada Passage, from the Sombrero Basin to the Lesser Antilles margin front. Our results reveal that this northeastern segment is an EW-trending left-stepping en-échelon strike-slip system that consists of the Sombrero and Malliwana pull-apart basins, the Malliwana and Anguilla left-lateral faults and the NE-SW compressional restraining bend at the Malliwana Hill.

Reviewing the structure of the Anegada Passage, from the South of Puerto-Rico to the Lesser Antilles margin front, reveals a polyphased tectonic history. A past NW-SE extension, possibly related to the rotation or escape of the PRVI block due to collision of the Bahamas Bank, and a currently active WNW-ESE strike-slip deformation associated to the shear component of the strain partitioning resulting from the subduction obliquity.