Indexed on: 09 Mar '16Published on: 17 Feb '16Published in: Journal of Quaternary Science
Multi‐proxy analyses on sediment cores from two closed basin lakes in the Serra Sul de Carajás were used to reconstruct environmental changes in south‐eastern Amazonia during the late Quaternary. The sediment record between 65 000 and 40 000 cal a BP (older dates with high level of uncertainty) is dominated by organic sediments intercalated with detritus (e.g. Al and Ti), indicating fluctuating lake levels related to changes in precipitation. A period of lower precipitation occurred from 40 000 to 35 000 cal a BP. Between ∼35 000 and 20 000 cal a BP, the dominance of detrital sediments suggests wetter and warmer conditions. However, iron enrichment in a siderite‐rich layer associated with the end of this period coincides with the Last Glacial Maximum, suggesting diagenetic changes in the profundal portion of the lakes and indicating a transition from oxidizing to reducing conditions. Subsequently, the period between ∼20 000 and 15 000 cal a BP was marked by a transition from drier to wetter climate, resulting in higher energy flows (e.g. Zr) and increased erosion of the basins. Another drier period was observed between ∼7000 and 3000 cal a BP (low detrital input and high Ca/Ti), when the lake levels were very low and eutrophication was high.