Résumé
In the frame of the ANR program GAARanti, aiming to track regional emersion surfaces and potential timing of land emersion or drowning, we conducted new field studies in islands belonging to the Anguilla Bank (Saint Barthelemy, Saint Martin, Tintamarre and Anguilla), the northernmost bank located in the forearc of the Lesser Antilles subduction zone and south of the Anegada passage. Our new micropaleontological, sedimentological and paleoenvironmental investigations allow a highly accurate calibration of the Neogene successions using large benthic foraminifers, planktonic foraminifers and calcareous nannofossils. We determine three main regional unconformities cropping out on the islands of the Anguilla bank. Interpretations of seismic lines acquired during the AntiTheSis (2016) and GARANTI (2017) cruises allow to reconstruct the tectono-sedimentary evolution of the offshore forearc basins, between South Saba Bank and Sombrero Basin. We use our well constrained onshore dataset and petroleum industry wells drilled in the Saba Bank to propose a constrained seismostratigraphy of offshore basins and onshore-offshore correlations. At regional scale, we identify three main unconformities dated: (1) Late Eocene, (2) Mid Miocene (ca 15 Ma) and (3) Zanclean (4 Ma). The Late Eocene unconformity is related to compressional tectonics and led to the emergence of most of our study area. Then subsidence occurred and topographic depressions were infilled by Oligocene to Early Miocene deposits, partly controlled by extensional fault activity along NW-SE and ENE-WSW faults systems bounding the Kalinago Basin and Anguilla Bank, respectively. The Mid Miocene unconformity is related to tectonics with increasing importance from south to north, thus probably related to the onset of the opening of Anegada Passage. This unconformity is related to emergence and erosion on the Anguilla and Saba Banks. The northern Antilles then subsided and most of basins reveal passive infilling during Middle Miocene to Pliocene. The Zanclean unconformity is related to localized uplifts that led to the final emergence of Anguilla, Tintamarre and St Martin carbonate platforms.