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Title: Reconstruções paleoambientais e paleoclimáticas durante o quaternário superior a partir de registros palinológicos ao sul do Pará (Brasil)
Other Titles: Paleoenvironmental and paleoclimate reconstruction during the upper quaternary through palynological records in south Pará (Brazil)
Keywords: Paleoclima;  Paleoambiente;  Lago;  Pleistoceno;  Holoceno;  Floresta;  Paleoclimate;  Paleoenvironmental;  Lake;  Pleistocene;  Holocene
Issue Date: 17-Jun-2013
Abstract: Palynological analyses are important to vegetation and climate reconstruction over time. A sediment core with 2,42 m of depth was collected in Lake Saci (South Pará, Brazil) in a region influenced by South Atlantic Convergence Zone (SACZ) to recognize the paleoenvironmental and paleoclimate dynamics since 35.000 years B.P. Six zones were established through the Saci-1 core from Lake Saci. Cluster analyses was realized by CONISS software and by variability ecological of pollen types, confirmed by sedimentological and geochemical parameters. The results indicate a low precipitation in the Amazon during the Pleistocene, between 35.000 and 29.870 years cal B.P. (zone SA-Ia). It is of according with the expansion of Savanna Herbs and reduction of Forest. Aquatic macrophytes (Sagittaria) were the edge of the lake and were important to increased lake productivity. However, between 29.870 and 18.190 years cal B.P. (zone SA-Ib), the drought was more pronounced, resulting in a reduction of Sagittaria. These plants were exposure in dry soil when the water level decreased. The Savannah Herbaceous still was predominant in this period, while the frequency of forest remains low. From 9.170 to 7.600 years cal B.P. (zone SA-II), the climatic conditions were more humid and warmer, evidenced by forest expansion and the appearance of Mauritia. Between 7.600 and 4.490 years cal B.P. (Middle Holocene) there was an increase of Poaceae. Pollen type of Savanna Wood, like Byrsonima, Curatella and Anadenanthera, is important to indicate a seasonal climate and event of fire. For some authors, this result can be related to the location further of north of the Zone Intertropical Convergence Zone (ITCZ). This provides more moisture to the north and dries to the south of amazon basin. The Zygnematales algae are important indicator to shallow water and low precipitation in the Middle Holocene. The moisture reappears between 4.490 and 1.740 years cal B.P., evidenced by the expansion of forest, composed by representatives adapted to periodic flooding. Between 1.740 and 1.305 years cal B.P., the more representative groups of the forest (Alchornea-Aparisthmium e Moraceae-Urticaceae), tolerant to reduced precipitation and low soil moisture, prevailed, constituting the Terra Firme Forest. Nevertheless, Celtis and Mauritia (Forest) and Poaceae were restricted because the less humid conditions, when compared with last zone (zone SA-IV).
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