International audienceA multiproxy analysis of lacustrine sediments cored in Grand-Case Pond at Saint-Martin, north of the Lesser Antilles archipelago, reveals three distinct climatic periods for the last 3700 years. From 3700 to ~2500 yr cal. BP and from 1150 yr cal. BP to the present, carbonate mud deposition occurred in connection with pond lowstands. These periods were also punctuated by severe drought events, marked by gypsum laminae, and hurricane landfalls, leading to marine sand inputs into the pond. The intermediate time interval, from 2500 to 1150 yr cal. BP, is typified by black organic mud deposition, suggesting that hypoxic to anoxic conditions prevailed at the pond bottom. These were probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today. The carbon isotopic composition of the ostracod Perissocytheridea bisulcata shows that the lowest δ13C values are recorded during the hypoxic periods, as a consequence of bacterial recycling of isotopically depleted organic matter. Such a climatic history agrees closely with that documented from other records in the Caribbean area, such as the Cariaco Basin, central coast of Belize or Barbados. By constrast, discrepancies seem to emerge from the comparison between hurricane activity recorded at Saint-Martin on the one hand and Vieques (Puerto Rico) on the other hand. We explain this apparent contradiction by a balance between two distinct storm paths in response to latitudinal shifts of the Intertropical Convergence Zone (ITCZ). Stronger storm activity over the Gulf coast and the inner Caribbean Sea is favoured by a southern position of the ITCZ in connection with dry climatic conditions. Plausible links with the North Atlantic Oscillation (NAO) are also suggested
Une séquence de vases lagunaires de l'étang de Grand-Case, à Saint-Martin (Petites Antilles), couvrant les quatre derniers millénaires, est analysée. Trois périodes climatiques et sédimentaires peuvent être distinguées : (1) une période globalement sèche (4200-2300 BP), caractérisée par le dépôt de vases carbonatées, de gypse et de lits sableux déposés par des cyclones ;(2) une période humide (2300-1150 BP), où dominent des vases organiques ; (3) une période récente (1150 BP jusqu'au présent), plus complexe et marquée par les activités humaines. Ces différentes phases trouvent leur correspondance dans les enregistrements livrés par d'autres lacs de l'aire Antilles-Mésoamérique. Les phénomènes climatiques impliqués, d'une part, dans les variations de fréquence des cyclones et, d'autre part, dans les variations de la pluviosité sur les Petites Antilles sont liés au déplacement de la zone de convergence intertropicale. Ces modifications climatiques pourraient constituer l'un des éléments d'explication des changements observés dans le peuplement de l'île de Saint-Martin.
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