Northern South America harbours a highly diversifi ed forest vegetation. However, it is not clear when this remarkable diversity was attained and how it was produced. Is the high diversity the product of a positive speciation-extinction balance that accumulated species over long time periods, or is it the product of high origination rates over short time periods, or both? Middle Cretaceous fl oras, although very poorly studied, are dominated by non-angiosperm taxa. By the Paleocene, pollen and macrobotanical fossils suggest that the basic phylogenetic composition and fl oral physiognomy of Neotropical rainforests were already present. Hence there was a profound change in Amazonian fl ora during the Late Cretaceous, that still needs to be documented. Levels of Paleocene diversity are much lower than those of modern tropical rainforests. By the Early Eocene, however, pollen diversity was very high, exceeding values of modern rainforests. At the EoceneOligocene a major drop in diversity coincided with an episode of global cooling. The palynological and palaeobotanical records of Amazonia suggest that high levels of diversity existed during the Miocene, a period when the boundary conditions for sustaining a rainforest (e.g. low seasonality, high precipitation, edaphic heterogeneous substrate) were met. The predecessor of the present rainforest was formed during the Paleogene and Neogene when the western Amazon lowlands were affected by Andean tectonism, which radically changed drainage systems and promoted wetland development. An overall global cooling during the Neogene also may have affected the rainforest, decreasing its area and expanding adjacent savanna belts. Recent events like the Quaternary ice ages also played a role in the forest dynamics and composition, although it seems to have been minor. In this chapter we will review the main characteristics of the Neogene palynological and palaeobotanical records in Amazonia, and we will make some comparisons with pre-and post-Neogene records. The data indicate that the Amazonian rainforest is more likely to be a product of a dynamic geological history stretching back over the past 25 million years rather than the last few hundred thousand years.

We report a new pleurodiran turtle from the Barremian Morro do Chaves Formation, Sergipe-Alagoas Basin, Brazil. We tested the phylogenetic position of Atolchelys lepida gen. et sp. nov. by including it in a comprehensive cladistic analysis of pleurodires. The new species is a basal member of Bothremydidae and simultaneously the oldest unambiguous crown Pleurodira. The biogeographic and chronostratigraphic significance of the finding has implications for the calibration of molecular clocks studies by pushing back the minimum age of crown Pleurodira by more than 12 Ma (ca 125 Ma). The reanalysis of Pelomedusoides relationships provides evidence that the early evolution and relationships among the main lineages of side-necked turtles can be explained, at least partially, by a sequence of vicariance events.

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Resumo As pesquisas realizadas nos últimos anos sobre os eventos magmáticos presentes nas bacias sedimentares brasileiras têm mostrado a importância desses episódios para a exploração de hidrocarbonetos. Citam-se os casos da geração (aquecimento), migração (alterações estruturais e petrográficas), acumulação (basaltos fraturados) e barreira (diques e soleiras) dos hidrocarbonetos, produzidos por essas rochas, tanto nas bacias sedimentares marginais como nas intracontinentais. O magmatismo é acompanhado pelo aumento da temperatura da bacia nos arredores de sua intrusão o que produz o aquecimento das rochas geradoras de hidrocarbonetos e, assim, possibilita a maturação da matéria orgânica nela contida. Ao mesmo tempo, tem sido verificado que os contatos diques / rochas sedimentares podem ter propiciado importantes caminhos para a migração dos hidrocarbonetos. Estudos recentes têm mostrado que o magmatismo deve merecer análises mais pormenorizadas até mesmo em suas manifestações extrusivas, tendo em vista as perspectivas de terem atuado como efetivos selantes e, em conseqüência, possibilitando a acumulação de hidrocarbonetos gerados nos sedimentos subjacentes. O magmatismo de caráter predominantemente básico a intermediário tem sua gênese na astenosfera, ou seja, abaixo da litosfera. Assim sendo, mesmo os diques que se introduziram no embasamento das nossas bacias sedimentares merecem cuidadosa atenção, posto que rochas são boas condutoras de calor e, sobre esses diques, podem ser prognosticados maiores gradientes geotérmicos presentes nos depósitos sedimentares sobrepostos. O melhor entendimento dos processos magmáticos presentes nas bacias sedimentares brasileiras deve conduzir a estudos sobre novas formas de exploração de hidrocarbonetos em nossas bacias sedimentares, inclusive naquelas em que as atividades de exploração tradicional não têm surtido os sucessos esperados. Palavras-chave:Bacias sedimentares brasileiras, magmatismo, exploração de petróleo. Abstract Magmatism in the brazilian sedimentary basins and the petroleum geology.In the recent years, the researches on the magmatic events that occurred in the Brazilian sedimentary basins had shown the importance of these episodes for the hydrocarbons exploration. The generation (heating), migration (structural and petrografic alterations), accumulation (basalt fractures) and migrations barriers (sills and dykes) of the hydrocarbons, produced for these rocks, are cited in the marginal and intracontinental Brazilian basins. The magmatism produce the temperature increase in the sedimentary basin, around its intrusion, and this propitiate the maturation of the organic matter contained in the hydrocarbons generating rocks of the basin. At the same time, has been verified that the contacts dykes/sedimentary rocks can represent important ways for the hydrocarbons migrations. Recent studies have shown that the magmatism, in its extrusive manifestations, can be analyzed in view of the possibility of having acted as effective hydrocarbon seals and, in consequence, makin...