Résumé
The Grenada Basin is a crescent-shape basin in a back-arc position relative to the Lesser Antilles arc. About 140 km wide, 3000 m deep and with a flat topography in its southern part, the basin shallows, narrows and becomes rougher northward. Its structural and genetic relations with the N-S-trending, ca.1000 m deep, Aves Ridge to the west, previously interpreted as the ante-Eocene remnant arc and the Lesser Antilles modern volcanic arc are debated. The GARANTI deep-seismic survey across the Grenada Basin (May-June 2017 French R/V L'Atalante), acquired two transverse (E-W) and one longitudinal (N-S), ca. 300 km long, wide-angle seismic lines shot using a 6473 in 3 seismic source array, and recorded by 40 ocean bottom seismometers together with ca. 3500 km of 720-traces seismic reflection lines. This data set revealed a clear asymmetry along both N-S and E-W directions. To the North and to the West, the crust beneath the basin is rather thick and non-oceanic, whereas it is probably oceanic to the southeast. We pay special attention to structural relations between the basin itself and the Aves Ridge in one hand and the Antilles Arc in the other hand. The basin is filled by up to 7 km of flat-lying sediments, thickening eastward and showing no apparent deformation. The Lesser Antilles arc margin is abrupt and does not appear to be the conjugate of the Aves Ridge margin. Fourteen dredges were collected, half of them were taken along the east flank of the Aves Ridge facing the deep Grenada basin. Evidences of past Cenozoic emersion of the Aves Ridge were found from drowned reef seamounts lying down to 1100 m bsl. Further analyses should better portrait the tectonic evolution of the Lesser Antilles back-arc area.