Papers by Egberto Pereira
Geochemical and foraminiferal data.
Anuário do Instituto de Geociências, 2007
Anuário do Instituto de Geociências - UFRJ, 2018
Os depósitos cenozoicos da porção emersa das bacias do Espírito Santo e de Mucuri mostram forte d... more Os depósitos cenozoicos da porção emersa das bacias do Espírito Santo e de Mucuri mostram forte deformação estrutural rúptil, sendo reconhecidos principalmente conjuntos de falhas N-S e NE-SO, de rejeito normal e variações NOSE e E-O, de rejeito transcorrente. As direções N-S e NE-SO são paralelas à orientação estrutural do rifte precursor das bacias da margem leste brasileira, enquanto as direções NOSE e E-O coincidem com as falhas transformantes e zonas de fraquezas oceânicas que acomodam a movimentação das placas litosféricas. Os dados estruturais levantados em afloramentos ao longo do norte do estado do Espírito Santo e na região costeira do sul da Bahia mostram que a configuração geomorfológica das falésias presentes no sul da Bahia foi controlada por falhas da fase rifte reativadas, além de estruturas transcorrentes ainda ativas que modelam o relevo atual. A atividade neotectônica de tais estruturas foi inferida através do reconhecimento de falhas afetando a cobertura sedimentar recente. A partir destes dados propõem-se novas interpretações estruturais para a porção emersa das bacias do Espírito Santo e de Mucuri e são avaliados os efeitos de tal deformação tectônica sobre a disposição litoestratigráfica dos depósitos estudados.
Revista Brasileira de Paleontologia, 2004
RESUMO-A partir das assembléias de miósporos e quitinozoários identificadas nos furos de sondagem... more RESUMO-A partir das assembléias de miósporos e quitinozoários identificadas nos furos de sondagem 269-R1 e 269-R2, foi possível realizar um biozoneamento detalhado, para o intervalo siluriano da bacia do Paraná na região do Paraguai Oriental, envolvendo os sedimentos do Grupo Itacurubí. Foram reconhecidas as biozonas de miósporos lmperfectotriletes e chulus-nanus. A biozona lmperfectotriletes, de idade neo-aeroniana/ eotelychiana, é coincidente com a parte inferior da biozona de quitinozoários Conochitina elongata (Aeroniano/ Eotelychiano). A biozona chulus-nanus (Telychiano/Wenlockiano) é correlata às biozonas de quitinozoários Salopochitina monterrosae-Conochitina proboscifera (Eotelychiana-Eossheinwoodiana) e com a parte superior da biozona Conochitina elongata (sub-biozona Conochitina proboscifera e Desmochitina cf. D. densa-transição Neo-Aeroniano-Eotelychiano). A assembléia de quitinozoários observada na parte superior dos furos estudados possibilitou uma datação mais precisa deste intervalo, definindo uma idade neotelychiana. Com relação à diversidade de espécies e o número de indivíduos descritos nos furos, pôde-se observar uma relação inversamente proporcional entre os esporos triletes e os criptosporos envoltos em membrana. Enquanto que a diversidade e o número de indivíduos de esporos triletes aumenta em direção ao topo do furo, os criptosporos envoltos em membrana apresentam uma relação inversa. Para estes, ocorre uma diminuição na diversidade e no número de indivíduos em direção ao topo do furo. As tétrades identificadas no furo 269-R1 possuem uma variação de tamanho aparentemente anômala quando comparadas àquelas descritas em diferentes trabalhos. Esta característica peculiar das espécies, observada neste estudo, pode estar associada a fatores ecológicos específicos desta parte do Gondwana ocidental, que se encontrava em condições periglaciais, durante o intervalo de tempo analisado.
Anuário do Instituto de Geociências, 1993
A análise estratigráfica do Paleozóico médio da sub-bacia do Alto Garças foi realizada a partir d... more A análise estratigráfica do Paleozóico médio da sub-bacia do Alto Garças foi realizada a partir do estudo dos sedimentos associados à formações Vila Maria Fumas e Ponta Grossa registrados em uma ampla faixa de exposição no sudoeste de Goiás, e pela interpretação dos dados dos poços AGse-1-MT, SAse-1-GO e TLst-1-MT da Petrobrás. Foi possível, a partir dessa análise, redefinir as relações estratigráficas entre as unidades litoestratigráficas envolvidas e estabelecer um arcabouço de seQüências
Pearson Correlations between the analysed data.
Fósseis Moleculares e Aplicações em Geoquímica Orgânica, 2022
Resumo O presente trabalho teve como objetivo o estudo geoquimico detalhado da Formacao Irati, at... more Resumo O presente trabalho teve como objetivo o estudo geoquimico detalhado da Formacao Irati, atraves do furo de sondagem PALEOSUL-05-SM-PR, localizado em Sao Mateus do Sul (PR). A partir dos dados de carbono orgânico total, enxofre total e residuo insoluvel, definiram-se sete unidades quimioestratigraficas para a Formacao Irati, nomeadas por letras de A a G. Analisaram-se, em cada unidade, o tipo de materia orgânica, pelo metodo pirolise “Rock-Eval”, e sua composicao, atraves do perfil dos alcanos. O ambiente deposicional foi caracterizado pela proporcao entre as abundâncias dos biomarcadores observados. Os intervalos referentes as unidades quimioestratigraficas C, D, F e G apresentaram grande potencial gerador (S2), sendo as unidades D e G as de maior potencial gerador para oleo (S2). Nas referidas unidades D e G, encontram-se os teores mais elevados de carbono orgânico total (COT) e indice de hidrogenio (IH). No entanto, todas as amostras analisadas apresentaram pouca evolucao t...
Extensive Pennsylvanian carbonate platforms are the main transgressive successions recorded on La... more Extensive Pennsylvanian carbonate platforms are the main transgressive successions recorded on Laurasia and Gondwana continents. The western Gondwana was one of the important sites of these transgressive carbonate accumulation exposed on several basins in Amazonia. Carbonate platform successions are exceptionally preserved in the southern border of the Amazonas Basin, northern Brazil, represented by the Pennsylvanian Itaituba Formation, previously interpreted as tidal flat, lagoon, and carbonate subtidal deposits. Microfacies and petrographic analysis of ~32 m-thick succession of core F5 allowed the definition of nine microfacies grouped in three facies associations: lagoon (FA1), bioclastic bars (FA2) and open carbonate platform (FA3). The FA1 is composed by massive lime-mudstones and dolostones with silt to sand-size terrigenous grains, brachiopods, echinoderms, and rare foraminifers. The lagoon deposits represent a low energy environment with intense micrite precipitation, low di...
Palaeogeography, Palaeoclimatology, Palaeoecology, 2021
Drowning unconformities are surfaces characterized on seismic data by high amplitude contrast bet... more Drowning unconformities are surfaces characterized on seismic data by high amplitude contrast between deepwater and shallow water facies. Such surfaces are created by the covering of the platform by onlapping siliciclastic sediments or other non-platform material. The key aspect of this paper is the application of the drowning unconformity concept, commonly used in marine settings, to a more restrictive one: the coquinas of the Itapema Formation, in the pre-salt succession of the Santos Basin (Brazil). In the studied area the sequence boundaries of the deposits related to the Itapema Formation are often associated with high reflectivity seismic horizons, which are tied to radioactive peaks of low-energy sedimentary facies in the gamma ray logs and also to the siliciclastic supply rate increase. However, the stratigraphic significance of these reflectors still lacks further investigation and an adequate description. In this way, it is proposed that the space-time filling of the Itape...
Anuário do Instituto de Geociências - UFRJ, 2020
Os foraminíferos têm sido usados como importante ferramenta para identificação de mudanças climát... more Os foraminíferos têm sido usados como importante ferramenta para identificação de mudanças climáticas ao longo de todo o Cenozoico, pois apresentam alto grau de preservação e respondem rapidamente às oscilações ambientais. O presente trabalho teve como objetivo identificar mudanças climáticas e variações da influência do mar, durante o Holoceno tardio, no estuário do rio Piraquê-Açu (ES, Brasil). O estudo baseou-se na caracterização das associações de foraminíferos bentônicos e nos resultados de δ13C e δ18O nas testas de Ammonia tepida realizadas nos testemunhos PA05 (2411 AP) e PA20 (1632 AP). Nos testemunhos foram identificadas 16 espécies de foraminíferos bentônicos, sendo algumas típicas de ambientes de plataforma continental (e.g. Lagena spp., Spiroloculina eximia, Oolina spp., Pyrulina gutta, Cibicidoides variabilis) e quatro espécies comuns aos ambientes estuarinos do Brasil (Ammonia parkinsoniana, A. tepida, Cribroelphidium excavatum e Bolivina striatula). Os resultados obti...
Proceedings of the 5 Simpósio Brasileiro de Geofísica, 2012
Cretaceous Research, 2020
Abstract In different basins around the world, organic-rich layers from the Cretaceous are being ... more Abstract In different basins around the world, organic-rich layers from the Cretaceous are being associated with perturbations in the global carbon cycle that reflect abrupt climatic and oceanic changes responsible for increased anoxia. In the northeastern part of Brazil, organic-rich rocks from the Parnaiba and Sao Luis basins—deposited during the late Aptian-early Albian and associated with the Codo Formation—offer an interesting stratigraphic record to evaluate the influence of oceanic anoxic events on restricted marine paleoenvironments. Therefore, an integrated study using different geochemical proxies (total organic carbon (TOC), Rock-Eval pyrolysis, δ13Corg, δ15Ntotal, and biomarkers) was conducted on sedimentary sections of the Sao Luis and Parnaiba basins (Codo Formation), which are assigned to the upper Aptian-lower Albian. The δ13Corg data obtained were compared with the isotopic δ13Corg profile from the section of the Santa Rosa Canyon (Mexico) where the record of the anoxic Aptian-Albian event (oceanic anoxic event 1b) was characterized. The stratigraphic record of the Codo Formation in both the basins presented the C11–C12 Cretaceous isotopic segments with clear 13Corg depletion associated with a spike in TOC that reached 10% at Parnaiba Basin and 15% at Sao Luis Basin. At Parnaiba Basin, biomarker results showed a high abundance of the terpane gammacerane, suggesting conditions of water-mass stratification and hypersalinity, setting that took place in the southern hemisphere during OAE 1b and enhanced preservation of organic matter in different basins. Also, marine sources were evidenced by the predominance of the C27 ααα(R) sterane and by the identification of the C30 ααα(R) sterane. In addition, the presence of the biomarkers C27 trisnorhopane 17β, C29αβ and C29 ααα (R) sterane reflect the contribution of terrigenous material to organic matter, which is commonly observed during anoxic events due to the acceleration of the hydrological cycle. Nitrogen isotopes revealed a relatively positive value (greater than 3%) which suggests anaerobic reduction of NO3- to N2 under suboxic to anoxic conditions (denitrification). Otherwise, a negative δ15N trend was observed in samples from the negative δ13Corg trend which represented a high organic carbon content. This δ15N signature suggests a decrease in the available NO3- (beginning of exhaustion) and an enhanced level of nitrogen fixation by microbial organisms during the anoxic event, which is also supported by a higher abundance of prokaryotic biomarkers (hopanes) in the organic matter.
Journal of Applied Geophysics, 2018
Machine learning approaches for petrographic classification of carbonate-siliciclastic rocks usin... more Machine learning approaches for petrographic classification of carbonate-siliciclastic rocks using well logs and textural information. Appgeo (2017),
Marine and Petroleum Geology, 2018
A 3D seismic volume was interpreted in order to study the extension of the Abrolhos magmatism in ... more A 3D seismic volume was interpreted in order to study the extension of the Abrolhos magmatism in the onshore portion of the Mucuri Basin, East-Brazilian continental margin. The effusive rocks were divided into two volcanic-sedimentary cycles that encompasses at least three igneous pulses, which were recognized in the well analyses. The seismic boundary between the volcanic-sedimentary cycles is marked by a strong negative amplitude reflector associated to the Lower Eocene Unconformity surface. Diffuse features similar to hydrothermal vents were also described, which would have been responsible for paleo-seepages in the marine Eocene sediments. The paleo-surface coincident with the top of these structures is directly related to the top of the first cycle of the onshore Abrolhos magmatism and, consequently, to the Lower Eocene Unconformity. The second volcanic-sedimentary cycle onlaps onto the mounds of the previews cycle and is limited at the top by the Pre-Upper Eocene Unconformity. The seismic analyses presented herein suggest that the relationship between the Cenozoic
Climate of the Past Discussions, 2019
Bituminous shales are associated to worldwide geological events, such as mass extinction, anoxia ... more Bituminous shales are associated to worldwide geological events, such as mass extinction, anoxia and climatic changes, mainly when preserved in carbonate ramps, and constitute reliable records of this dynamics. However, a minority of data still exist that measure the Permian, especially in the Southern Hemisphere associated to Panthalassic Ocean as compared to numerous studies of Oceanic Anoxic Events in the Cretaceous or associated to Tethys. The Late Permian extinction was the most severe extinction of the past 500 million years, which wiped out over 90% of marine species. Before the Permian-Triassic boundary (e. g. Early-Middle Permian successions) geochemical and geological anomalous aspects has received more attention due the information about the Late Paleozoic icehouse-greenhous transitions, which is one of the triggers for the catastrophic ectinction. Therefore the Irati Formation, Permian interval of Paraná Basin in southern Brazil, is suitable for the study of these intricate processes due to the presence of Permian bituminous shales and carbonates. Based on core descriptions, spectral gamma ray data and organic geochemistry, a stratigraphic scheme is here proposed to support paleoenvironmental inferences. We identified three depositional sequences formed internally by T-R cycles of highest frequency. The sedimentary facies analysis indicates a carbonate ramp subdivided into outer, middle and inner. Climatic and sea level changes are defined, and also oscillations in the salinity, oxygenation and organic matter source. Bituminous shales record normal salinity, with anoxia levels and even euxinia, associated to the increase in bioproductivity. Carbonate facies register periods of hypersalinity under oxic environment and semi-arid conditions. The accumulation of Mesosaurus skeletal remains results from the action of reworking fluxes, creating an endemic facies in this region. Climatic versus eustatic influence were differentiated, and also the controlling hierarchies. These results are evidence for the environmental dynamics from the Permian, that generated extreme global events, mainly in Gondwana. 1 Introduction Black shales are associated to both regional and global geologic events, such as climatic changes, oceanic anoxia and mass extinction (Hotinski et al., 2001; Phelps et al., 2015). Over the Earth´s history, the anoxic events were concomitant with significant perturbations in the global carbon cycle, influencing the carbon dioxide (CO 2) concentration both in the atmosphere and in the oceans (
IEEE Geoscience and Remote Sensing Letters, 2019
Identification of underground formation lithology from well-log data is an important task in petr... more Identification of underground formation lithology from well-log data is an important task in petroleum exploration and engineering. Due to the cost or imprecision of some methods applied in this activity, there is a need to automate the procedure of reservoir characterization. Machine learning techniques can be efficient alternatives to lithology identification. To acquire proper performance, usually, some parameters of these techniques should be adjusted, and this can become a hard task depending on the complexity of the underlying problem. This letter integrates the gradient boosting (GB) with a differential evolution (DE) for formation lithology identification using data from the Daniudui gas field and the Hangjinqi gas field. This letter's contributions include the use of an evolutionary algorithm to adjust optimally the hyperparameters of the GB, and the results show improvements when compared with those obtained in the literature.
Journal of Applied Geophysics, 2018
Fig. 2. Scheme illustrating the over and undersampling. a) Undersampling consists in dropping obs... more Fig. 2. Scheme illustrating the over and undersampling. a) Undersampling consists in dropping observations of the majority class (Class 1) in order to obtain a balanced dataset. b) Oversampling consists in duplicating the samples of the minority class (Class 2) in order to obtain a balanced dataset.
Journal of Sedimentary Environments, 2017
Santos Basin is located in the southeast of the Brazilian continental margin and was created by r... more Santos Basin is located in the southeast of the Brazilian continental margin and was created by rifting processes during the Gondwana break up and opening of the South Atlantic, initiated in the Neocomian (Cretaceous). The area gained renewed attention from the oil industry due to recent Petrobras' huge discoveries of carbonate reservoirs below the salt layer (Pre-salt). The discovery of this new play in deep and ultra-deep water opened a new exploratory frontier in Brazil, generating excellent economic prospects for the country. The case study of this work is the Lapa Field, discovered in 2007 by Petrobras, which is located in deep water and represents one of the largest producing fields of the Pre-salt. This research aims to improve the actual model for the tectono-stratigraphic evolution of the Pre-salt section on the Santos Basin (Brazil). The used database includes the public data provided by National Petroleum Agency (ANP; six post-stack 2D seismic lines migrated in time and four wells). Main Pre-salt horizons and faults were mapped considering the Exxon Model to do the seismic-stratigraphy interpretation. A velocity model was constructed for the Lapa field, which enable the generation of isopach maps. All these products allow a better visualization of the tectonostratigraphic evolution of the region and also show the salt thickness variation, analyzing the reason of its behavior.
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Papers by Egberto Pereira