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Hydrological changes related to the variability of tropical South American climate from the Cabo Frio lagoonal system (Brazil) during the last 5000 years

Abstract : From west to east, the Fluminense coastline, composed of two series of lagoons, presents an aridity gradient induced by a local upwelling that is controlled by trade winds coming from the south Atlantic. The physico-chemical conditions of the lagoons are controlled by the duration of the dry season. They are characterized by hypersaline conditions with organic-carbonate sedimentation in the upwelling-influenced area, and by hyposaline conditions with organic-detrital sedimentation out of the upwelling-influenced area. On a core collected in the Brejo do Espinho hypersaline lagoon, diatom analysis supported by sedimentological data revealed a varying high water level from 4500 to 2200 14C yr BP induced by successive freshwater inputs in to the lagoon. Two major dry events occurred during this period, probably related to relative sea-level fluctuations. At 2200 14C yr BP, a drastic change occurred, as indicated by a carbonate nodule, carbonate-dominated sediments and poly- to hypersaline diatoms, all suggesting arid conditions. The Brejo do Espinho record suggests that before 2200 14C yr BP, the central part of the Brazilian coast was mostly subjected to south to southeasterly winds and weaker trade winds, whereas after 2200 14C yr BP, trade winds dominated, implying drier conditions at the easternmost part of the Fluminense coastline. These results would also suggest a late Holocene increase in El Niño activity (after 2200 14C yr BP), consistent with several El Niño records from western South America.
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Submitted on : Monday, May 1, 2006 - 8:55:01 AM
Last modification on : Monday, October 19, 2020 - 2:34:03 PM

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Florence Sylvestre, Abdelfettah Sifeddine, Bruno Turcq, Isabelle Martins, Ana Luiza Spadano Albuquerque, et al.. Hydrological changes related to the variability of tropical South American climate from the Cabo Frio lagoonal system (Brazil) during the last 5000 years. The holocene, London: Sage, 2005, 15 (4), pp.625-630. ⟨10.1191/0959683605hl823rr⟩. ⟨hal-00023576⟩

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