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In this study, we traced past oceanographic changes in the southeastern Brazilian Continental Margin based on the ratio between two planktonic foraminifera species (Globigerina bulloides and Globigerinoides ruber), along a core located close to the transition between the tropical and subtropical biogeographic provinces. Each species is representative of a biogeographic province and has excluding ecological preferences. According to our interpretation, periods of low G. bulloides/G. ruber values would characterize a stronger influence of the warm, oligotrophic tropical water and, conversely, periods of high G. bulloides/G. ruber values correspond to a stronger influence of colder and nutrient-richer waters. Changes in the relative influence of the different water masses are strongly dependent on the regional wind field which affects the upper-level circulation mostly by the latitudinal displacement of the bifurcation of the South Equatorial Current which, in turn, has strong impacts on the Brazil Current's strength and on the intensity of the upwelling regime in the study area. The analysis of the last 30 kyr record, suggests that productivity was highly increased both around the Last Glacial Maximum and the Younger Dryas event. In between these events, the record suggests that productivity was severely decreased during deglaciation. Also, our record suggests a gradual decrease in productivity from 11 kyr BP through the Holocene which can be explained by a progressively stronger Brazil Current resulting from a southward displacement of the Intertropical Convergence Zone. Our results are consistent with other studies providing estimates of changes in trade wind strength and in the extent of the climatic belts through time. RESUMO - No presente estudo, analisamos mudancas paleoceanograficas na Margem Continental Brasileira a partir da analise da razao entre duas especies de foraminiferos planctonicos (Globigerina bulloides e Globigerinoides ruber), ao longo de um testemunho localizado proximo a transicao entre as provincias biogeograficas Tropical e Subtropical. Cada especie e representativa de uma provincia biogeografica e possui preferencias ecologicas proprias. De acordo com a nossa interpretacao, periodos de baixa razao G. bulloides/G. ruber caracterizariam uma maior influencia de aguas quentes e oligotroficas enquanto, periodos de alta razao G. bulloides/G. ruber corresponderiam a uma maior influencia de aguas frias e ricas em nutrientes. Variacoes na influencia relativa das diferentes massas d'agua sao fortemente dependentes do campo de ventos regional o que afeta a circulacao superficial, principalmente pelo deslocamento latitudinal da bifurcacao da Corrente Sul Equatorial. Isto determina a intensidade da Corrente do Brasil e do regime de ressurgencia na area de estudo. A analise do registro dos ultimos 30 mil anos sugere que a produtividade aumentou significativamente ao redor do Ultimo Maximo Glacial e do evento Younger Dryas. Entre ambos eventos, o nosso registro sugere que a produtividade diminui severamente durante a deglaciacao. O registro tambem sugere uma diminuicao gradual da produtividade desde 11 mil anos atras ao longo do Holoceno, o que pode ser explicado por uma Corrente do Brasil progressivamente mais intensa, resultante de um deslocamento para o sul da Zona de Convergencia Intertropical. Os resultados sao consistentes com outros estudos que proporcionam estimativas de mudancas na intensidade dos ventos alisios e na extensao dos cinturoes climaticos ao longo do tempo.

Tracing past circulation changes in the western South Atlantic based on planktonic foraminifera