Physical, chemical and geochemical characteristics of lacustrine sediments were studied to reconstruct paleohydrologyical control on sedimentation in an amazonian floodplain. a core was collected at the Lago Grande de curuai floodplain, in the Santa Ninha Lake, located on the right margin of the amazon river at 850 km of the estuary. Water content, granulometry, radiocarbon dating, organic carbon, nitrogen content and δ13c were used to characterize the sedimentary processes. The core is 270 cm-long which corresponds to 5600 cal years BP. The core points out different sedimentary environments: flooded vegetation at the base of the core till 4900 cal years BP is substituted by grass banks changing to a floodplain encompassing prolonged annual dryness at 4000 cal years BP. Since 600 cal years BP, the present day Varzea Lake, permanently over flooded, has been installed.