Holocene paleoenvironmental reconstruction in the Eastern Amazonian Basin: Comprido Lake

Two sediment cores were studied from Comprido Lake, a black water floodplain lake located near Monte Alegre City, Eastern Amazonian Basin. The total organic carbon (TOC), nitrogen content (TN), δ13CTOC, sedimentary chlorophyll, diatom record and mineralogical composition revealed different hydrological and climatic regimes during the Holocene. Between 10,300 and 7800 cal yr BP, a dry climate was suggested by low values of TOC and chlorophyll derivatives concentrations that are related to the development of a C4 grasses on unflooded mud banks. A gap in sedimentation due to a complete dryness of the lake occurred between 7800 and 3000 cal years BP corresponding to the Middle Holocene dry phase. From 3000 cal years BP onwards a gradual increase of the TOC, chlorophyll derivatives and Aulacoseira sp. suggest an increase in the productivity and in water lake level due to the high water flow of the Amazon River and the catchment area as well. The Comprido Lake record indicates that the Late Holocene in this region was characterized by a wetter climate, as also observed in other records of the Amazonian Basin.

► We analyze the Holocene environmental history of Comprido Lake, Eastern Amazonia.
► During the Early Holocene a dry climate was suggested by the presence of C4 plants.
► The middle Holocene was characterized by a complete drying of the lake.
► A higher water level of the Amazon River during the Late Holocene was recorded.
► Fluvial hydrological changes influenced the organic sedimentation in Comprido Lake.