Upwelling influence in the evolution of the siliciclastic-carbonate sedimentation of hypersaline lagoonal systems in Rio de Janeiro state, Brazil.

Brejo do Espinho and Lagoa Vermelha are both hypersaline lagoons located along the coast of Rio de Janeiro State (Brazil), which are characterized by the presence of extensive microbial mat growth, stromatolites and dolomite precipitation over at least 3,000 yrs B.P. The current semi-arid microclimate of the region influenced by the upwelling system, is crucial for carbonate precipitation, and investigations about its climate condition and this relation to the carbonate precipitation have been conducted in this area. The aim of this project is reconstructing the paleoenvironmental and paleoclimatic conditions triggering the precipitation of primary dolomite and microbial mat/stromatolite formation on Brejo do Espinho and Lago Vermelha during the Holocene and currently, through sediments and water parameters. The results of this research will help to understand the relation between the biomineralisation processes involved in carbonate precipitation, organic matter source and quality to local climate variations associated with the degree of upwelling intensity. To achieve these goals we plan to analyze the dissolved organic matter from water samples during the annual cycle to define the relation between the lipid-lagoon water and salinity by δD, and other mineralogy, elementary composition, organic analyses and radiocarbon dating.