The Amazon basin provides 20% of the total fresh water worldwide and the reconstruction of its paleohydrologic changes is essential for the global paleo-environment. The Amazon River and its tributaries are followed along their upward and downward course by several floodplains lakes that cover a large area around 300 – 500 000 km² (5 to 8% of the total surface area of the Amazon Basin). The floodplains lakes are built due to the fluctuations in the level of the rivers, which causes the formation of bars and accumulation of sediment carried by the rivers and its tributaries. Thus, significant quantities of organic matter can accumulate within these lakes that might represent important carbon sinks. The aim of this work is to evaluate the importance of past climatic changes on sedimentation process in Amazonia floodplain lakes and to determine the role played by the climatic driving forces on the carbon sink. Here, we present data from the sedimentary record of the greatest Amazon floodplain lake (Curuai floodplain) that reveal the presence of rapid and marked paleohydrological changes during the Holocene in the Amazon Basin. For this work, seismic profiles (3.5 khz) and eight sedimentary cores were studies in the floodplain system. The cores were analyzed using radiocarbon dates, mineralogy, apparent density, organic carbon concentration, C/N ratio and ?¹³C. Our results point out two important events, at 5700 cal yr BP and 2700 cal yr BP, characterized by high sedimentation rates that indicate deep changes in the floodplain hydrology. Seismic and sedimentation data seem to indicate that these changes are due to abrupt climatic events. Both events provoked significantly high carbon accumulation in the floodplain system.