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-(Palynomorphs of the sedimentary profile of a bog, São Francisco de Paula, Eastern Plateau of Rio Grande do Sul, southern Brazil). This paper aims at giving basic reference material to the study of plant succession in the Quaternary Brazilian southern plateau. Therefore, it presents the palynological analysis of 22 samples, taken along one sedimentary profile of 286 cm, in a bog of Rio Grande do Sul Eastern Plateau, corresponding approximately to the last 25000 years. The chemical processing of the samples followed the conventional method and the analysis was made by light microscopy. Palynomorphs corresponding to 10 fungi, 6 algae, 3 bryophytes and 16 pteridophytes were examined. The material, especially spores, is described and illustrated. The descriptions are accompanied, whenever possible, by ecological data of the original organism.

Baseado no registro de cocolitoforídeos do testemunho sedimentar SIS 188, recuperado do talude da Bacia de Pelotas, este trabalho buscou esclarecer a relação entre a deposição de carbonato e da matéria orgânica com a produtividade primária, assim como identificar os processos oceanográficos que a regula ao longo dos eventos climáticos marcantes do Quaternário tardio. O testemunho analisado contém os Estágios Isotópicos Marinhos 1, 2 e 3. As espécies Florisphaera profunda, habitante da zona fótica inferior, Emiliania huxleyi e Gephyrocapsa spp. dominam a associação ao longo de todo o intervalo. As ocorrências secundárias de Calcidiscus leptoporus e Helicosphaera spp. (as quais possuem afinidade com condições de ressurgência) e Umbilicosphaera spp. (que apresenta preferência por ambientes oligotróficos e coluna d´água estratificada) auxiliaram na interpretação da produtividade. Os cocolitoforídeos contribuíram para a transferência de carbonato e matéria orgânica para o fundo oceânico. Entretanto, especialmente durante o EIM 3, a deposição de carbono orgânico parece ser controlada principalmente pelas propriedades químicas das massas d'água de fundo. Durante o EIM 3, a associação de cocólitos também é influenciada pela velocidade da corrente de fundo, que os transporta juntamente com os sedimentos. As condições de fundo mudam durante o EIM 2, permitindo o acúmulo de cocólitos, CaCO 3 e COT. No EIM 1, especialmente no Holoceno, todos os proxies apontam para um intervalo de maior produtividade.

-In this work, fossil assemblages of coccolithophorids, oxygen stable isotopes (Globigerinoides ruber), and radiocarbon dating were used as proxies. The sediment core, obtained on the slope of Campos Basin, was analyzed, comprising the last 130 kyr. The results show that placolith-bearing taxa, such as Gephyrocapsa spp. and Emiliania huxleyi, as well as Florisphaera profunda, which inhabits the lower photic zone, dominated the assemblage during the whole study interval. Over the past 130 kyr, there was a relationship between productivity (based on N ratio) and climate cyclicity. In a general way, it can be said that sensu stricto interglacial stages (MIS 5e and the Holocene) showed low productivity, while the others (MIS 5d-a, 4, 3 and 2) had large fl uctuations. During interglacial-like conditions, a northward shift in the Intertropical Convergence Zone position would take place, along with a weakening of the NE winds associated with the Southern Atlantic Subtropical High and a weakening of the Brazil Current, leading to the maintenance of the water stratifi cation. On the other hand, during glacial-like conditions, the inverse conditions would be favorable to a shallower nutricline, increasing productivity in surface waters. Maximum productivity is achieved between 14-6.5 ky (during deglaciation), which could be a refl ection of the events of the Last Glacial Maximum.Key words: paleoceanography, coccolithophorids, productivity, Quaternary, Southwestern Atlantic.RESUMO -Neste trabalho, assembleias fósseis de cocolitoforídeos, isótopos estáveis de oxigênio (Globigerinoides ruber) e datações radiocarbônicas foram usados como proxies. Um testemunho sedimentar obtido no talude da bacia de Campos foi analisado, compreendendo os últimos 130 ka. Os resultados mostram que táxons placolitoformes, como Gephyrocapsa spp. e Emiliania huxleyi, bem como Florisphaera profunda, que habita a zona fótica inferior, dominam a assembleia durante todo o intervalo estudado. Ao longo dos últimos 130 ka há uma relação entre a produtividade (baseada na razão N) e a ciclicidade climática. De uma maneira geral, pode ser dito que estágios interglaciais sensu stricto (EIM 5e e o Holoceno) mostraram baixa produtividade, enquanto os outros (EIM 5d-a, 4, 3 e 2) apresentaram grandes fl utuações. Durante condições do tipo interglacial, uma migração para o norte da posição da Zona de Convergência Intertropical, juntamente com um enfraquecimento dos ventos de nordeste associados à Alta Subtropical do Atlântico Sul e um enfraquecimento da Corrente do Brasil, possivelmente levava à manutenção da estratifi cação das águas. Por outro lado, durante condições do tipo glacial, as condições inversas favoreceriam uma nutriclina mais rasa, aumentando a produtividade das águas superfi ciais. O máximo de produtividade foi registrado entre 14-6,5 ka (durante a deglaciação), o que pode ser um refl exo de eventos do Último Máximo Glacial.Palavras-chave: paleoceanografi a, cocolitoforídeos, produtividade, Quaternário, Atlântico Sudoeste.

Mechanisms of fertilization inferred from the coccolithophorid record during the Late Quaternary in the southern Brazilian Continental Margin. This study aimed to understand which fertilization mechanisms are preponderant over oceanic primary productivity and its relationship with remarkable climatic events of the Late Quaternary in the south of the Brazilian Continental Margin. The investigation was carried out through geochemical and coccolithophorid analyzes in the SIS188 marine core, recovered from the Pelotas Basin slope at 1,514 m water depth. The record shows that productivity was related to insolation (with a predominance of the precession cycle) and atmospheric processes that influence ocean dynamics. During the glacial period (MIS 3 and 2), the highest productivity intervals were associated with the expansion of the upwelling system in the Santa Marta Cape region, driven by the northeast winds. However, the interval of greatest productivity recorded in the core is the initial Holocene, when the upwelling was attenuated. This substantial increase in productivity is attributed to lagging processes resulting from the decrease in sea level that occurred during the Last Glacial Maximum. Keywords: productivity, Pelotas Basin, upwelling, Quaternary, coccolithophorids.

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Morphometric analysis in the shells of the planktonic foraminifera Orbulina universa: a source for paleoceanographic information? In this study, we describe morphometric analyses of Orbulina universa morphotypes presently found in the Western South Atlantic, and their relation to the upper water thermohaline indexes. We also investigate this relationship under glacial and interglacial conditions between 7.2 and 32 kyr BP. Ten plankton samples distributed between 32º55' and 26º20'S were selected for the analyses of modern O. universa specimens. Core SIS188 was retrieved at 29º22'S, 47º28'W enabling the analysis of 21 fossil samples. Shell diameter, pore diameter, pore density and porosity were measured using SEM images. Chronology of core SIS188 is based on four AMS 14 C ages and the planktonic foraminifera oxygen isotope curve. Planktonic foraminifera relative abundances were converted into SST data using the Modern Analog Technique (MAT). Correlations between the morphometric parameters and temperature and salinity of surface Waters (modern samples) or paleotemperature (fossil samples) were calculated. Morphological characteristics of the analyzed shells allowed to differentiate two morphotypes of O. universa, namely Caribbean and Mediterranean in the studied region. For the Caribbean morphotype, the large pore density showed a negative correlation with both temperature and salinity. For the Mediterranean morphotype, no significant correlations were found. For fossil samples, no significant correlations were found between summer SST (0-50m) and morphometric parameters for the Caribbean or the Mediterranean morphotypes. Possibly, other genotypes do exist in the fossil record, so modern and fossil morphotypes would not have the same behavior. Another explanation for the absence of correlation in fossil samples are errors associated with the SST estimates. Furthermore, fossil samples could represent distinct and more complex oceanographic conditions compared to current configuration, with Plata Plume Water and Brazil Malvinas Confluence migration playing a most significant role in the past.

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