Palynological studies of Late Holocene Jurujuba Sound sediments (Guanabara Bay), Rio de Janeiro, southeast Brazil

The Late Holocene vegetation history and climate from southern (SE) Brazil have been reconstructed by means of a pollen analysis of a 223 cm-long core from the central part of Jurujuba Sound (22°55256S and 43°06346W). The analysis showed that before 3520 yr BP (subzone Ia), tropical rainforest occupied extensive parts of the region. However, from 3520 yr BP onwards, the forest reduced in size and there was a slight increase in pollen from hygrophyte plants, fern spores and algae. The higher sea level during this period favoured the expansion of these plants, as well as Botryococcus, in the flooded areas around the Sound. There was a reduction in palynomorph concentrations at about 2820 yr BP (subzone Ib). This can probably be related to a regressive event of the relative sea level and the reduction of atmospheric precipitation during this period. This event favoured an increase in grassland formations, and pioneer forest elements seemed to settle in the open areas. The intensive human occupation in the region around Jurujuba Sound was clearly evident in the pollen record next to the core top (at zone II). The low percentage of tree pollen grains showed that the Atlantic rainforest was significantly reduced in size, while there was an expressive increase in the herbaceous pollen that is associated with the appearance of exotic taxa.