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Abstract:
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.
