The Toarcian Oceanic Anoxic Event (T-OAE) is marked by major paleoenvironmental and paleoceanographical changes at a global scale, associated to a severe disturbance of the global carbon cycle, and organic-rich facies deposition. Here, a multi-proxy approach (petrographic and geochemical techniques) was applied to the study of the organic content of the T-OAE of the Paris Basin, whose phytoplanktonic origin has been previously inferred by its geochemical signature.The top of tenuicostatum Zone is characterized by palynomorphs and marine phytoplankton-derived amorphous organic matter (AOM), representing a proximal marine environment with emplacement of euxinic conditions to the top (total organic carbon/sulfur content and increase in AOM). At the base of the serpentinum Zone the proliferation of bacterial biomass begins, with phytoplankton playing a secondary role. This indicates the development of stagnant and restrictive conditions in a proximal environment, with water column stratification (neohop-13(18)-ene). The majority of the serpentinum Zone is dominated by bacterial biomass, suggesting a marine environment with bottom waters stagnation, possibly related to basin paleogeomorphology and circulation patterns, with episodic euxinia.This therefore suggests that the T-OAE organic fraction is dominated by bacterial biomass, not phytoplankton, showing the importance of an integrated approach to the determination of the organic facies.
Choanoflagellates are microeukaryotes that inhabit freshwater and marine environments and have long been regarded as the closest living relatives of Metazoa. Knowledge on the evolution of choanoflagellates is key for the understanding of the ancestry of animals, and although molecular clock evidence suggests the appearance of choanoflagellates by late Neoproterozoic, no specimens of choanoflagellates are known to occur in the fossil record. Here the first putative occurrence of choanoflagellates in sediments from the Cretaceous (Cenomanian–Turonian) is described by means of several cutting-edge petrographic techniques, and a discussion of its paleoenvironmental significance is performed. Furthermore, their placement in the organic matter classification systems is argued, with a placement in the Zoomorph Subgroup (Palynomorph Group) of the dispersed organic matter classification system being proposed. Regarding the ICCP System 1994, incorporation of choanoflagellates is, at a first glance, straightforward within the liptinite group, but the definition of a new maceral may be necessary to accommodate the genetic origin of these organisms. While modern choanoflagellates may bring light to the cellular foundations of animal origins, this discovery may provide an older term of comparison to their extant specimens and provide guidelines for possible identification of these organic components in other locations and ages throughout the geological record.
Este texto apresenta o projeto “Saberes, textualidades e visualidades interculturais: potencialidades de tramas-grafias para retomadas epistêmicas”, realizado no âmbito do Núcleo Takinahaky de Formação Superior Indígena, da Universidade Federal de Goiás. Ele tem como eixo a noção de “Retomada Epistêmica” e se desenvolve por meio de atividades acadêmicas vinculadas ao estudo do tema contextual: Terra, território e sustentabilidade. O objetivo da proposta é pensar, problematizar e produzir conhecimento sobre o território, entendido tanto em relação aos espaços originários, como em relação ao espaço acadêmico. Em seguida, busca-se problematizar processos de violência epistêmica, presentes nos distintos espaços. Nesse sentido, por meio do campo expandido das artes visuais, apresentamos imagens-conhecimentos que expressam e produzem relações entre saberes indígenas e não indígenas e refletem sobre a presença indígena em espaços acadêmicos.
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