Did, and when, the Aves Ridge (Eastern Caribbean) emerge and subsequently sink ?

The Aves Ridge is a N-S trending, submerged plateau, except for the Aves Island, in the present-day back-arc of the Lesser Antilles subduction system that separates Grenada and Venezuela basins. It is considered as the southern prolongation of the Great Antillean Arc and recorded a magmatic activity between late Cretaceous and Paleogene. Middle Eocene to early Miocene marine carbonate platform and late Miocene to Pleistocene pelagic sediments were also dredged or cored along the Aves. Previous paleogeographic reconstructions proposed that it was emerged between either 59 and 49 Ma (Stephan et al., 1990) or 35 and 33 Ma (Iturralde-Vinent & Mc Phee, 1999), mainly on the basis of a submarine or aerial unconformity at DSDP Site 148 and volcaniclastic conglomerates alleged continental. Recent dredges allow providing for the first time evidences for its emersion and further drowning.

During the GARANTI cruise, 6 dredges were performed on the eastern flank of the Aves Ridge. The study of benthic and planktonic foraminifera within dredged limestones points to Lutetian-Bartonian (P14-P17, 39.2- 33.9 Ma) and Aquitanian (N4-N5a, 23.03-20.4 Ma) reef, fore reef, inner ramp carbonate platform deposits and to Serravalian (N12, 13.8-12 Ma) to Calabrian-Holocene (N22-N23, 1.8-0 Ma) outer ramp/basin deposits. The study of the diagenesis of the carbonate platform limestones revealed that they suffered an early marine episode followed by a phreatic vadose and then a last marine episodes. The phreatic vadose diagenetic episode is very well documented in all dredged sites by dissolution cavities, iron coatings and speleothems infilling of dissolution cracks, thus indicating emergence of the carbonate platform. The last marine diagenetic episode is characterized by the occurrence of phosphatic phases. Stable isotopes measurements on calcite from speleothems yield slightly negative dO¹⁸ (-0.81 ± 0.39) whereas early cements and latest micrites show positive ones (+1.51 ± 0.93 and +4.07 ± 0.15, respectively). The slightly negative dO¹⁸ signature of speleothem is concordant with the signature of meteoric waters at the same latitude (-1.07 +/- 1.81 at Barbados). We also manage to date the emersion and the drowning by U/Pb measurements on calcite speleothems and on apatite cement. This work is part of the GAARAnti ANR-17-CE31-0009 project.