Pollen analysis of a sediment sample obtained at 222 cm from the top of a drilling core collected in the Bay of Guanabara, Rio de Janeiro, was used as a tool to obtain more knowledge about pre-historical human living and environment. 14 C datation revealed the age of 4210 years B.P. Most frequent pollen grains came from plants like Alchornea (Euphorbiaceae), Celtis (Ulmaceae), Lecythidaceae, Meliaceae, Ochnaceae and spores from forest Pteridophyta. Palynology and environmental studies revealed that agricultural activities could not be detected. The dense tropical rain forest was the dominant vegetation occurring in this region.

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Aiming to investigate the deposition of pollen grains and spores in Guanabara Bay, Rio de Janeiro State, 61 surface sediment samples were analyzed. The results showed that the current deposition of palynomorphs in surface sediments of Guanabara Bay represents the regional vegetation of this hydrographic basin. The differential distribution of palynomorphs followed a pattern influenced by bathymetry, tidal currents speed, discharge of numerous rivers, and by human activity. The dominance of representatives of Field Vegetation reflects the changes of the original flora caused by intense human activities in the region. The continued presence and richness of pollen types of rain forest in the samples indicates that their source area might be the vegetation from riparian border of rivers in the western sector of the Bay, where the mangrove vegetation is being preserved. The large amount of damaged palynomorphs may be related to abrasion that occurs during river transport, indicating removal or reworking from their areas of origin.

RESUMO-O presente trabalho tem como objetivo caracterizar os processos de sedimentação atual que controlam a deposição de palinomorfos em vários setores da baía de Guanabara, Rio de Janeiro. Foram coletadas 27 amostras de sedimentos superficiais dentro da baía e tratadas pelo método palinológico por peneiramento e, em seguida, pelo método padronizado para sedimentos quaternários. Os resultados obtidos apresentaram um percentual maior de tipos polínicos relacionados à vegetação campestre e uma grande riqueza de tipos polínicos da floresta ombrófila/mata atlântica. A distribuição diferencial dos palinomorfos seguiu um padrão influenciado pela batimetria, associado ao padrão de correntes gerado pelas marés, os quais promoveram a maior concentração dos palinomorfos nas áreas mais profundas e em locais de obstrução topográfica. A deposição diferencial, em relação ao tamanho dos palinomorfos, seguiu um padrão de acúmulo de palinomorfos de tamanho pequeno nas áreas de maior energia dos fluxos aquáticos e os de tamanho grande em áreas de águas mais calmas, lateralmente à desembocadura dos rios.

ResumoO trabalho tem como objetivo identificar e descrever a morfologia de tipos polínicos ocorrentes nos sedimentos superficiais da Baía de Guanabara, Rio de Janeiro, Brasil. A análise palinológica possibilitou identificar 91 tipos polínicos, sendo 5 de gimnospermas e 86 de angiospermas. Com base nos dados polínicos e ecológicos obtidos neste trabalho será possível contribuir para o reconhecimento das formações vegetais e a caracterização da vegetação ao longo do Holoceno. Palavras chave: Holoceno; Baía de Guanabara; Palinologia AbstractThe study presents the description and identification of pollen grains obtained in the top sediments of Guanabara Bay, Rio de Janeiro, Brazil. Pollen analysis enabled to identify 91 pollen types, with five of gymnosperms and 86 of angiosperms. The pollen and the ecological data obtained in the present work will contribute to the recognition of the vegetal formations and the characterization of the vegetation throughout the Holocene.

The sediment of a core collected about 2 km north of Paquetá Island, Guanabara Bay, was submitted to pollen analysis, in order to recognize the dynamics of the regional vegetation, and the anthropic influence. Radiocarbon dating of a sample next to the bottom of the core indicates an age of 4.210 ± 40 14 C yrs B.P (calibrated age). It was possible to establish four palynological zones. Starting at the bottom of the core, a decrease in palynomorph concentration, the presence of degraded pollen grains and spores, and the predominance of ombrophilous forest pollen grains were observed in the basal portion of Zone I. These data may indicate the presence of an exuberant Atlantic Forest, dominated by a marine regressive event. The concentration of well-preserved palynomorphs increased in Zone II, with the predominance of the ombrophilous forest vegetation also, and an expressive increase of hygrophytes, indicating more humid environmental conditions. Palynomorph concentration decreased again toward the top of Zone III, and the fi eld vegetation was predominant. In the upper Zone IV occurred a strong decrease in pollen and spore concentration, with predominance of fi eld vegetation also, and the appearance of exotic pollen grains, showing the anthropic influence at this time.

The study of palynofacies along a core drilled on the coastal plain of Cabo Frio, State of Rio de Janeiro, was carried out in order to contribute to the knowledge of the paleoenvironmental evolution of the Pero Beach region. The ages obtained from 14 C datings allowed to verify that the studied core records the past 6761 ± 130 yrs cal BP. Thirty samples were prepared by standard methodology for palynofacies. About three hundred particles of the particulate organic material was classified and recorded for each sample. Statistical methods were employed for the associations of particulate organic matter (R-mode cluster analysis) and levels (samples; Q-mode cluster analysis) analyzed along the core. Furthermore, the ratio Phytoclast-Total Organic Carbon (Phy-TOC) was used to verify the proximity of the source area. The three major groups of particulate organic matter found along the studied core are Phytoclasts, Amorphous Organic Matter (AOM) and Palynomorphs. The samples showed in general, a predominance of phytoclasts (73.2%), followed by AOM (18.6%) and Palynomorphs (8.2%). Supported by statistical analysis, it was possible to deduce that the study area evolved since the middle Holocene from a marine environment to a paleolagoon.