Oblique collision of buoyant provinces against subduction zones frequently results in individualizing and rotating regional-scale blocks. In contrast, the collision of the Bahamas Bank against the Northeastern Caribbean Plate increased the margin convexity triggering forearc fragmentation into small-scale blocks. This deformation results in a prominent >450-km-long sequence of V-shaped basins that widens trenchward separated by elevated spurs, in the Northern Lesser Antilles (NLA, i.e. Guadeloupe to Virgin Island). In absence of deep structure imaging, various competing models were proposed to account for this faults-bounded Basins-and-Spurs System. High-resolution bathymetric and deep multichannel seismic data acquired during cruises ANTITHESIS1-3, reveal a drastically different tectonic evolution of the NLA forearc.

During Eocene-Oligocene time, the NLA margin accommodated the Bahamas Bank collision and the consecutive margin convex bending by trench-parallel extension along N40-90°-trending normal faults, opening V-shaped valleys in the forearc. Backarc spreading in the Kalinago Basin and block rotations went along with this tectonic phase, which ends up with tectonic uplifts and an earliest-middle Miocene regional emersion phase. Post middle Miocene, regional subsidence and tectonic extension in the forearc is partly accommodated along the newly-imaged N300°-trending, 200-km-long Tintamarre Normal Faults Zone. This drastic subsidence phase reveals vigorous margin basal erosion, which likely generated the synchronous westward migration of the volcanic arc. Thus, unlike widely-accepted previous theoretical models, the first deep seismic images in the NLA forearc show that the NE-SW faulting and the prominent V-Shaped valleys result from a past and sealed tectonic phase related to the margin bending and consecutive blocks rotation.