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Previous issue date: 2007-03-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Baixo Vermelho area, situated on the northern portion of Umbuzeiro Graben (onshore Potiguar Basin), represents a typical example of a rift basin, characterized, in subsurface, by the sedimentary rift sequence, correlated to Pend?ncia Formation (Valanginian-Barremian), and by the Carnaubais fault system. In this context, two main goals, the stratigraphic and the structural analysis, had guided the research. For this purpose, it was used the 3D seismic volume and eight wells located in the study area and adjacencies.
The stratigraphic analysis of the Valanginian-Barremian interval was carried through in two distinct phases, 1D and 2D, in which the basic concepts of the sequence stratigraphy had been adapted. In these phases, the individual analysis of each well and the correlation between them, allowed to recognize the main lithofacies, to interpret the effective depositional systems and to identify the genetic units and key-surfaces of chronostratigraphic character. The analyzed lithofacies are represented predominantly by conglomerates, sandstones, siltites and shales, with carbonate rocks and marls occurring subordinately. According to these lithofacies associations, it is possible to interpret the following depositional systems: alluvial fan, fluvio-deltaic and lacustrine depositional systems. The alluvial fan system is mainly composed by conglomerates deposits, which had developed, preferentially in the south portion of the area, being directly associated to Carnaubais fault system. The fluvial-deltaic system, in turn, was mainly developed in the northwest portion of the area, at the flexural edge, being characterized by coarse sandstones with shales and siltites intercalated. On the other hand, the lacustrine system, the most dominant one in the study area, is formed mainly by shales that could occur intercalated with thin layers of fine to very fine sandstones, interpreted as turbidite deposits. The recognized sequence stratigraphy units in the wells are represented by
parasequence sets, systems tracts and depositional sequences. The parasequence sets, which are progradational or retrogradational, had been grouped and related to the systems tracts. The predominance of the progradation parasequence sets (general trend with coarsening-upward) characterizes the Regressive Systems Tract, while the occurrence, more frequently, of the retrogradation parasequence sets (general trend with finning-upward) represents the Transgressive System Tract. In the seismic stratigraphic analysis, the lithofacies described in the wells had been related to chaotic, progradational and parallel/subparallel seismic facies, which are associated, frequently, to the alluvial fans, fluvial-deltaic and lacustrine depositional systems, respectively. In this analysis, it was possible to recognize fifteen seismic horizons that correspond to sequence boundaries and to maximum flooding surfaces, which separates Transgressive to Regressive systems tracts. The recognition of transgressive-regressive cycles allowed to identify nine, possibly, 3a order deposicional sequences, related to the tectonic-sedimentary cycles. The structural analysis, in turn, was done at Baixo Vermelho seismic volume, which shows, clearly, the structural complexity printed in the area, mainly related to Carnaubais fault system, acting as an important fault system of the rift edge. This fault system is characterized by a main arrangement of normal faults with trend NE-SO, where Carnaubais Fault represents
the maximum expression of these lineations. Carnaubais Fault corresponds to a fault with typically listric geometry, with general trend N70?E, dipping to northwest. It is observed, throughout all the seismic volume, with variations in its surface, which had conditioned, in its evolutive stages, the formation of innumerable structural features that normally are identified in Pendencia Formation. In this unit, part of these features is related to the formation of longitudinal foldings (rollover structures and distentional folding associated), originated by the displacement of the main fault plan, propitiating variations in geometry and thickness of the adjacent layers, which had been deposited at the same time. Other structural features are related to the secondary faultings, which could be synthetic or antithetic to Carnaubais Fault. In a general way, these faults have limited lateral continuity, with listric planar format and, apparently, they play the role of the accomodation of the distentional deformation printed in the area. Thus, the interaction between the stratigraphic and structural analysis, based on an excellent quality of the used data, allowed to get one better agreement on the tectonicsedimentary evolution of the Valanginian-Barremian interval (Pend?ncia Formation) in the studied area / A ?rea de Baixo Vermelho, localizada na por??o norte do Graben de Umbuzeiro (Bacia Potiguar emersa), representa um exemplo t?pico de uma bacia do tipo rifte, caracterizada, em subsuperf?cie, pela seq??ncia sedimentar rifte, correlata ? Forma??o Pend?ncia (Valanginiano-Barremiano), e pelo Sistema de Falhas de Carnaubais. Dentro deste contexto, duas abordagens principais nortearam o estudo, a estratigr?fica e a estrutural, em que se lan?ou m?o da interpreta??o do volume s?smico 3D de Baixo Vermelho e de oito po?os explorat?rios da ?rea e adjac?ncias. A an?lise estratigr?fica do intervalo do Valanginiano ao Barremiano foi realizada em duas fases distintas, 1D e 2D, nas quais foram adaptados os conceitos b?sicos da estratigrafia de seq??ncias. Nestas fases, a an?lise individual de cada po?o e a correla??o entre os mesmos permitiu reconhecer as principais litof?cies presentes, interpretar os sistemas deposicionais vigentes e identificar as unidades gen?ticas e as superf?cies-chave de car?ter cronoestratigr?fico. As litof?cies analisadas constituem, predominantemente, conglomerados, arenitos, siltitos e folhelhos, ocorrendo, ainda, de forma subordinada, rochas carbon?ticas e margas. Com base nas associa??es destas litof?cies foram interpretados os sistemas deposicionais de leque aluvial, fl?vio-deltaico e lacustre. O sistema de leque aluvial ? composto, principalmente, por dep?sitos conglomer?ticos, os quais se desenvolveram, principalmente, na por??o sul da ?rea, estando diretamente associados ao Sistema de Falhas de Carnaubais. O sistema fl?viodeltaico, por sua vez, foi desencadeado, preferencialmente, na por??o noroeste da ?rea, na margem flexural, sendo caracterizado por arenitos grossos a finos intercalados a folhelhos e siltitos. Em contrapartida, o sistema lacustre, o mais dominante na ?rea investigada, ? formado principalmente por folhelhos que ocorrem, por vezes, intercalados a delgadas camadas de arenitos finos a muito finos, interpretados como dep?sitos turbid?ticos. As unidades da estratigrafia de seq??ncias reconhecidas nos po?os est?o representadas pelos conjuntos de parasseq??ncias, tratos de sistemas e seq??ncias deposicionais. Os conjuntos de parasseq??ncias, ora progradacionais, ora retrogradacionais, foram agrupados e relacionados aos tratos de sistemas. A predomin?ncia dos conjuntos de parassequ?ncias progradacionais (trend geral com engrossamento textural para o topo) caracteriza o Trato de Sistemas Regressivo, ao passo que a ocorr?ncia, com maior freq??ncia, dos conjuntos de parassequ?ncias retrogradacionais (trend geral com afinamento textural para o topo) representam o Trato de Sistemas Transgressivo. Na an?lise sismoestratigr?fica, as litof?cies descritas nos po?os foram relacionadas ?s sismof?cies ca?tica, progradacional e paralela/subparalela, as quais se associam, freq?entemente, aos sistemas de leques aluviais, fl?vio-deltaico e lacustre, respectivamente. Nesta an?lise foram mapeados quinze horizontes s?smicos que correspondem aos limites de seq??ncias deposicionais e ?s superf?cies de inunda??o m?xima, que separam o trato de sistemas transgressivo do regressivo. O reconhecimento de ciclos transgressivo-regressivo permitiu identificar nove seq??ncias deposicionais, possivelmente de 3a ordem, relacionadas a ciclos tectono-sedimentares. A an?lise estrutural, por sua vez, foi realizada no volume s?smico de Baixo Vermelho, que mostra, com clareza, a complexidade estrutural impressa na ?rea, relacionada, principalmente, ao Sistema de Falhas de Carnaubais, que atua como um importante sistema de falhas de borda de rifte. Este sistema de falhas ? caracterizado por um arranjo principal de falhas normais NE-SO, em que a Falha de Carnaubais representa a express?o m?xima destes lineamentos. A Falha de Carnaubais corresponde a uma falha com geometria tipicamente l?strica, direcionada segundo o trend geral N70?E, mergulhando para noroeste. Apresenta-se, ao longo de todo o volume s?smico, com varia??es em sua superf?cie, as quais condicionaram, em seus est?gios evolutivos, a forma??o de in?meras fei??es estruturais, que s?o comumente identificadas na Forma??o Pend?ncia. Nesta unidade, parte das fei??es est? relacionada ? forma??o de dobramentos longitudinais (estrutura do tipo rollover e dobramentos distensionais associados), decorrentes do deslocamento do plano da falha principal, propiciando varia??es na geometria e espessura dos estratos adjacentes, os quais foram depositados sincronicamente. Outras fei??es estruturais est?o relacionadas a falhamentos secund?rios, tanto sint?ticos quanto antit?ticos ? Falha de Carnaubais. De uma maneira geral, estas falhas t?m continuidade lateral limitada, com formato planar a l?strico e, aparentemente, desempenham o papel de acomoda??o da deforma??o distensional imposta na ?rea. Assim, a intera??o entre as an?lises estratigr?fica e estrutural, alicer?ados pela excelente qualidade dos dados utilizados, permitiu obter um melhor entendimento sobre a evolu??o tectono-sedimentar do intervalo Valanginiano ao Barremiano (Forma??o Pend?ncia) na ?rea de estudo
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/18740 |
| Date | 30 March 2007 |
| Creators | Salviano, Katiane dos Santos |
| Contributors | CPF:59176911691, http://lattes.cnpq.br/8212523609187259, Sousa, Debora do Carmo, CPF:91530962404, http://lattes.cnpq.br/3244080713189448, Matos, Renato Marcos Darros de, C?rdoba, Val?ria Centurlon |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Geodin?mica e Geof?sica, UFRN, BR, Geodin?mica; Geof?sica |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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