Late Quaternary vegetation and climate dynamics in southeastern Amazonia inferred from Lagoa da Confusão in Tocantins State, northern Brazil

Late Quaternary vegetation and climate dynamics have been reconstructed by pollen analysis of a lacustrine sediment core from Lagoa da Confusão. The lake lies about 160 km southwest of Palmas, capital of Tocantins State. The study area is located in the cerrado (savanna) and cerrado/Amazon rain forest transition region of southeastern Amazonia. The record, dated by 4 AMS radiocarbon dates, provide insight into vegetation and climate dynamics of late Pleistocene and Holocene age. Pollen data indicate that the study region was dominated by cerrado (savanna), fìrst of the campo limpo type (grassland savanna) between 60,300-51,700 (chronology A) or 29,000-27,400 (14)C yr B.P. (chronology B) and than of the campo sujo type between 51,700-24,670 (chronology A) or 27,400-14,000 (14)C yr B.P. (chronology B). Existing small areas of gallery forests increased slightly during the second period. Amazon forest taxa occurred sparsely in the study region. The palaeovegetation infer a markedly drier climate (low precipitation and long annual dry season) during the glacial periods compared to the modern climate. A sedimentary gap probably occurred during the full glacial and/or Lateglacial period, suggesting drier climatic conditions than during the two earlier periods. During the early and mid Holocene the campo cerrado type (savanna woodland) was dominant and the landscape was more forested by the stronger presence of gallery forest and Amazon forest trees. Precipitation was higher, and the length of the annual dry season was shorter than during the late Pleistocene periods. After 5460 (14)C yr B.P. campo cerrado was still dominant, but forest cover increased markedly by the expansion Amazon forest populations and palm trees, reflecting the wettest climate period recorded. The results from Lagoa da Conlusão support the general trend of dry glacial conditions, as reported from other tropical South American lowland regions. The expansion of the Amazon rain forest since the mid Holocene in northwestern and southwestern Amazonia is now also confirmed for the southeastern Amazon region