Programa de Pós-Graduação em Geodinâmica e Geofísica
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Doctoral Thesis Geomorfologia e arquitetura interna do vale inciso do Rio Açu na bacia potiguar imersa (NE Brasil)(Universidade Federal do Rio Grande do Norte, 2012) Gomes, Moab Praxedes; Vital, Helenice; Macedo, José Wilson de Paiva; http://lattes.cnpq.br/8074712340427454; Costa Neto, Leão Xavier; http://lattes.cnpq.br/1059276496317561; http://lattes.cnpq.br/3595069999049968; http://lattes.cnpq.br/2086362176219605; Xavier Neto, Pedro; http://lattes.cnpq.br/0420885770350995; Caldas, Luciano Henrique de Oliveirac; http://lattes.cnpq.br/1850164003052269The tectonic-sedimentary framework of a marginal basin contains traces of the marine and continental history of certain portion of planet Earth. The evolution of passive margins, specifically on continental shelves, has been intensively studied over the last century, because of the economic and scientific interests. Moreover, the recent methodological and technical advances in field data collection and analysis have transformed shallow marine studies from descriptive to quantitative and based on integration of different datasets. This Thesis presents the integration of multidisciplinary data (Landsat images, gravimetry, altimetry, singlebeam bathymetry, sonography, shallow seismic, sedimentology, current measurements and observations by SCUBA diving) which allowed the analysis of geomorphological expression of the northern Continental Shelf of the Rio Grande Norte state (NE-Brazil) and its correlation with their last phases of sedimentation in the context of the submerged Potiguar Basin, including sea-level fluctuations in the Quaternary, pre-Holocene subaerial exposure, the establishment of the Holocene currents on continental shelf, and pre-Cenozoic tectonic fault reactivation. This shelf is shallow, narrow and can be divided into inner, middle and outer shelf, and displays several geomorphological features. Its geometry and morphology is controlled by neotectonics. On it, there is an incised valley of the Rio Acu, a key element in the last stratigraphic record of Holocene transgression. The morphology of the Açu incised valley aligns with the central axis of Potiguar Basin and is strongly influenced by neotectonics in the context of the Domain Equatorial Atlantic Margin. The incised valley-fill was controlled by the morphology during transgression, as well as the morphology constraints the hydrodynamic processes and dispersal of siliciclastic and carbonate sediments during periods of highstand. Patch reefs, with coraline algae colonies were found between 20 and 40 m water depth. It allowed inferences about the mixed sedimentation in the Pleistocene and Holocene. These results contribute to the study of paleo-environmental conditions of the Quaternary, analogues reservoirs, shallow marine depositional models of high-energy tropical shelf, hydrocarbon exploration, geotechnical, environmental matters, navigation and others.Master Thesis Morfodinâmica de um campo de dunas eólicas costeiras no município de Maxaranguape-RN(Universidade Federal do Rio Grande do Norte, 2011-01) Paiva, Hanyel Pessoa; Amaral, Ricardo Farias do; http://lattes.cnpq.br/5120081491389865; http://lattes.cnpq.br/2004093766044463The present study is the analysis of transport measurements using wind collectors of sand (Sand Traps) over a field of sand dunes on the Maracajaú’s beach, city of Maxaranguape. These measures are used, then as a parameter of wind movement in this region. Seven field trips were conducted between September 2009 and September 2010 to obtain data from 12 stations along the collectors Dunefield Maracajaú and weather data with the use of portable weather station. Were also used data from the meteorological station Maxaranguape corresponding to April 2008 until May 2010, provided by the Instituto Nacional de Pesquisas Espaciais - INPE for Information about the frequency and intensity of the winds in the region. The data were processed and analyzed using statistical techniques of regression and correlation to measure the wind drift of Dunefield Maracajaú. The analysis of data from the meteorological station of Maxaranguape points with winds SE quadrant of the preferred direction and ESS for the whole period. This same station recorded 78% of wind speeds above 5 m / s, over three quarters of the total wind, showing a strong wind capacity to transport sand. The calculations show that wind drift of the field collections made in September 2010, are those that indicate a greater movement of sediment in the wind field Maracajaú dunes with 0.439 kg of sand transported per hour. Then, with decreasing values of sedimentary wind movement, are the collections made in February 2010 with winds carrying capacity equal to 0.239 kg per hour in September 2009 with a transport capacity of wind 0.06334 kg per hour in October 2009 recording of aeolian transport capacity of 0,025 kg per hour, in December 2009, with winds carrying 0.0064 kg per hour, and last and least significant collections held in March 2010, where he registered a load carried by the wind of 0.0032 kg. Finally it is proposed to adjust the methodology used.Master Thesis Modelagem geológica e geofísica tridimensional de reservatórios: exemplo de um campo petrolífero da bacia potiguar (NE do Brasil)(Universidade Federal do Rio Grande do Norte, 2010-02-25) Costa, Patrícia Rose de Carvalho; Antunes, Alex Francisco; http://lattes.cnpq.br/1519973126832391; Córdoba, Valéria Centurion; http://lattes.cnpq.br/8212523609187259; http://lattes.cnpq.br/5487417149395339; Pérez, Yoe Alain Reyes; http://lattes.cnpq.br/8835402837157614The geological reservoir modelling, considered an important step to the understanding of oil fields, comprises the description of the characteristics of the oil-bearing poro-perm systems allowing, among otherthings: (i) to construct an integrated framework of all available data; (ii) to assess the needs of acquiring new data; (iii) to quantify volumes of hydrocarbons; (iv) to assist in the location of new wells, and (v) to support the flow simulation and thus to define better inferences about reservoir performance. In this context, this thesis presents the various steps involved in building a three- dimensional geological model of a reservoir from an oil field of Potiguar Basin. The steps consisted, first, by the well data analysis, followed by seismic data analysis and, finally, by the geological modelling itself. During the well data analysis it was performed the quality control analysis of the logs aiming the exclusion of spurious values; stratigraphic correlation between wells with interpretation of basin units and hydrocarbon reservoir zones; analysis of petrophysical and core data, and characterization of electrofacies for the reservoirs. During the seismic data analysis, it was carried out the correlation between wells (depth range) and seismics (time scale); seismic interpretation of regional horizons; seismic inversion to improve the data quality; creation of a velocity model for data conversion from time to depth; seismic interpretation of the reservoir zones defining their top and bottom horizons, and seismic attributes analysis. The research culminated with the construction of the structural model, followed by facies and petrophysical models (porosity and permeability) and, finally, with the oil volume calculation for the reservoir zones and uncertainty analysis of the calculated volumes.Master Thesis Associações de Foraminíferos e Padrões Sedimentares da Plataforma Externa do Rio Grande do Norte, NE-Brasil(Universidade Federal do Rio Grande do Norte, 2018-12-13) Andrade, Allany de Paula Uchôa; Eichler, Patrícia Pinheiro Beck; Gomes, Moab Praxedes; ; ; ; Srivastava, Narendra Kumar; ; Tabosa, Werner Farkatt;Foraminifera as tools have contributed to the investigation of sedimentary processes, carbonate productivity, water quality, nutrient intakes and environmental health of continental shelves. Here we show how foraminiferal associations are influenced by nutrients and abiotic factors that control the carbonate production in the modern outer shelf of Rio Grande do Norte, in the region of Açu Reefs. Granulometric analysis, CaCO3 and organic matter content allowed us to identify six sedimentary facies. Quantitative and qualitative biologic data were used on the univariate and multivariate statistical analyzes. The presence of the planktonic foraminiferal species Globigerina rubra, and the benthic species Quinqueloculina patagonica, and Peneroplis pertussus is related to the intrusion of ocean currents over the shelf break. The presence of Buccella peruviana is correlated with high CaCO3 and organic matter contents. It was observed that the diversity of symbiotic organisms is related to carbonate production and the pristine shelf environment. These foraminiferal species indicate the occurrence of oceanic phenomena under the influence of Tropical Gyre and resurgence.Master Thesis Morfodinâmica de sistemas de ilhas barreiras tropicais, litoral setentrional-RN(2019-08-23) Silva, Filipe Ezequiel da; Vital, Helenice; ; ; Silva, André Giskard Aquino da; ; Costa Neto, Leão Xavier da;The northern littoral of Rio Grande do Norte State (RN) is a tropical mixed energy coast where geological conditioning favors the maintenance of barrier island systems. These systems include barrier islands, sandy spits, ebb tidal deltas, mangrove forests, tidal inlets and plains. Coastal dynamics in these systems is intense, which causes large shoreline retreat, sandy spits growth, as well opening and closure of tidal inlets in a short time. This dynamic directly affects onshore oil exploration, and for this reason, several studies have been conducted in the region in recent decades, in order to better understand its morphodynamic aspects. However, much remains to be understood, especially when considering the extension of these systems. This work aimed to evaluate the morphodynamics of the barrier islands systems of the northern coast of RN through quantitative data obtained from multitemporal analysis of orbital images of Landsat 5 TM and Landsat 8 OLI sensors, and associated knowledge of coastal processes as well. The analysis were carried in a period of 33 years (1984 to 2016), with 4-year sampling intervals for the low frequency analysis, and 1 year for the high frequency analysis. The results indicate a great influence of the sampling interval on the interpretation of the evolutionary behavior of these barrier islands and sandy spits, so that low frequency analysis does not represent the actual evolution of the barriers, leading to misinterpretations. This is related to the considerably dynamic behavior of these barriers which over a period of 1 year may present a 3 km² magnification. In addition, the successive alternations between enlargement and shrinkage in the area of these barriers correspond to uninterrupted accretion and erosion cycles that nullify any trends of growth or decrease in these areas. The morphodynamic analysis allowed differentiating two types of barriers: migrant and stationary. The migration movement results from the joint action of the meteo-oceanographic forcing that causes continuous updrift sediment loss followed by downdrift sediment gain. This process pushes the whole barrier westward at rates of up to 100 meters per year, however preserving its shape. The migration of barriers can cause opening, rotation, translation and closure of tidal channels. The stationary barriers, in turn, have features that attenuate the energy of waves and currents, avoiding large sediment losses and, consequently, their migration. The barriers also act as sediment source for the transgressive dune fields. Therefore, migrating islands may coalesce with the shoreline providing sediment to adjacent dune fields.Master Thesis Distribuição sedimentar e geomorfologia da plataforma interna adjacente ao estuário do Rio Açu, Macau-RN(2019-03-27) Paiva, Pedro Thiago de Moura; Vital, Helenice; ; ; Almeida, Narelle Maia de; ; Perez, Yoe Alain Reyes;The tropical semi-arid estuarine systems have a scarce sediment supply, but contribute to the deposition and development of sedimentary reserves at its mouths. Thus, the coastline and estuary undergo the depositional and erosional processes influenced by sediment supply and hydrodynamic. The estuarine zones have a high population density and are a region very vulnerable. The region of study develops socioeconomic activity focused on tourism, fishing, shrimp farming, oil industry, etc. This work aims to understand the submarine geomorphology, associated sediment distribution, and hydrodynamic performance as well, located on the inner shelf adjacent to Açú, a tropical semi-arid estuary on the Brazilian NE. The databank consisted of single-beam bathymetry, side-scan sonar records, surface sediment samples and satellite images. In the inner continental shelf were identified 8 textured patterns associated with 8 sedimentary facies, and 1 textural pattern as submerged rocky outcrops. In the shelf, the coverings of the siliciclastic and bioclastic facies are deposited in different places, influenced by the morphologies, estuarine performance and hydrodynamic. Thus, the siliciclastic facies (composed of mud and sand) are deposited in the regions in from of the Açú River mouth, and on the other hand, the bioclastic facies are located in the eastern portions of the area, but also associated with siliciclastic facies. The morphological diversity developed in the shelf is correlated with the sea level rise and fall, where the main features identified are sand ridges, incised valley, sand and mud banks, superimposed by lower order morphologies, such as, wavy relief with the presence of subaqueous 2D dunes and ripples. The tidal currents and wave trend direction are consistent with the subaqueous 2D dunes and ripples, respectively. In addition, the diversity of the ripples orientations in the Açú River mouth indicates a higher complexity of the currents and waves in this region.Doctoral Thesis Sismologia de fonte passiva na bacia do Parnaíba: implicações para a subsidência cratônica(2019-12-17) Coelho, Diogo Luiz de Oliveira; Casas, Jordi Julia; ; ; Nascimento, Aderson Farias do; ; Assumpção, Marcelo Sousa de; ; Fontes, Sérgio Luiz; ; Medeiros, Walter Eugênio de;In this thesis we present different methodological approaches that characterize the crustal structure and the Mantle Transition Zone in order to elucidate the main geodynamic processes that operate in and under the Parnaíba Basin. Point estimates of crustal thickness and Vp Vs ratio, together with S-wave velocity profiles, obtained from receiver function analysis at various seismographic stations within the basin show a thick crust near the current depocenter caused by a high-velocity seismic layer located at the crust/mantle boundary. The basin’s crustal structure matches that of Precambrian terrains worlwide and suggests minimal crustal stretching in the east-west direction. Imaging of the Mantle Transition Zone (MTZ) through migration of receiver functions, on the other hand, rules out deep convective processes under the basin as responsible for its cratonic subsidence, as the constrained MTZ thickness remains uniform under the basin. Another finding that rules out vertical asthenospheric flow driving basin subsidence is the shallowing of the 660 km discontinuity under the Cambrian rifts near the Transbrasiliano Lineament. This upwarp is indicative of a thermal anomaly at the base of the Transition Zone, but not at the top where no change is observed. The addition of new crustal and mantle constraints for the Parnaíba Basin represents our main contribution to the present debate on its origin and cratonic evolution, and we expect that they will contribute in the future to unveiling the processes that determined the evolution of this basin over geological time.Master Thesis Modelagem numérica de esforços flexurais no Nordeste do Brasil(2019-12-02) Leite Neto, Gilberto da Silva; Ferreira, Joaquim Mendes; ; ; Castro, David Lopes de; ; Lima Neto, Heleno Carlos de;We model the contribution of the stresses generated by the topography and density heterogeneities in the stress field of NE Brazil, and the interplay between these and regional stresses. Our model consists of a horizontally-layered elastic slab (the lithosphere) that floats above an inviscid fluid (the asthenosphere), where the surface load is generated by the topography and bathymetry, and the internal loads are calculated from the Bouguer anomalies. The deviatoric flexural stresses are calculated in the Fourier domain. Our results showed local flexural stresses with magnitudes comparable to those of the tectonic plate-wide stresses, and mainly controlled by the lateral density variations associated to the long-wavelenghts Bouguer anomalies. Scenarios for the total stress field were calculated by superposing different values for an E-W-oriented regional compression. We predict the stress axes orientations and stress regimes for the equatorial margin and for the Pernambuco Shear Zone (PESZ) region, although we highlight the importance of spreading stresses, not considered in this work, in rotating the maximum horizontal compression (SHmax) predictions. The prediction of stress regime and stress axes orientation in PESZ using low to zero regional compression suggest that a decoupling of the shallow stresses from the plate-wide stresses might occur in this region. Other possible explanation found was that the spreading stresses might counterbalance the regional stresses. We conclude that the superposition of principally flexural and platewide stresses explains reasonably the observed stress regimes and SHmax orientations in great part of NE Brazil. Furthermore, flexural stresses are playing an important role in the reactivation of the PESZ, possibly controlling the stress field.Master Thesis Morfologia e distribuição de dunas submersas do estuário do Rio Potengi (Natal-RN)(2019-12-13) Belchior, Flávia Valânea Souza; Gomes, Moab Praxedes; ; ; Silva, André Giskard Aquino da; ; Tabosa, Werner Farkatt;O Rio Potengi estende-se por mais de 170 km e deságua no litoral oriental do Rio Grande do Norte, sendo sua região estuarina cercada pela região metropolitana da cidade de Natal. O canal principal tem sofrido com dragagens periódicas e suas margens com intensa urbanização. Tais interferências influenciam diretamente a dinâmica sedimentar estuarina, resultando na redistribuição de zonas de erosão e assoreamento. Devido ao regime semi-diurno de mesomaré, a circulação do estuário é dominada por correntes de vazante e enchente que imprimem, em diferentes zonas do canal estuarino, padrões de formas de fundo e dunas subaquosas que evidenciam o transporte de sedimentos e as modificações na morfologia do canal. O objetivo principal desse trabalho é analisar a espacialização, a morfologia das feições de fundo e investigar os processos morfo-sedimentares. Foram utilizados dados sonográficos e batimétricos adquiridos no canal principal do estuário em agosto de 2017 por meio de um sonar interferométrico (Edgetech 4600), operando na frequência de 540 KHz, com capacidade de varredura de 7 vezes a profundidade. Os dados sonográficos foram processados utilizando os softwares SonarWiz 6 que permitiu gerar o mosaico e a interpretação das zonas e formas de fundo, mapas e modelos 3D. Os dados batimétricos foram filtrados utilizando o software Hypack 2014 afim de obter os perfis batimétricos. O estuário possui um canal principal assimétrico com profundidades variando de 3 m a 15 m à montante e à jusante, respectivamente. Foram mapeadas formas de fundo ao longo do estuário como dunas 2D, dunas 3D, dunas de pequeno, médio e grande porte, fundo plano e feições rígidas. Os fundos planos lisos e rugoso são comuns nas margens do canal com profundidade variando de 2 a 6 m. Além disso, são encontrados na região central circundando dunas 2D. Tanto as dunas 2D como as 3D são dunas assimétricas e variam de acordo com o espaçamento entre elas: de 0,6 a 5 m (pequeno porte), 5 a 10 m (médio porte) e de 10 a 100 m (grande porte). Ambas têm suas profundidades variando de 6 a 12 m. Apesar dessas dunas serem bem distribuídas por todo canal, as 2D tem maior predominância em relação as 3D. Os resultados indicam que as formas de fundo encontradas estão relacionadas com diferentes fluxos atuantes no canal, conferindo uma distribuição irregular das feições sedimentares.Master Thesis Aplicação de sistema de análise de linha de costa (Digital Shoreline Analysis System) para avaliação de mudanças costeiras no delta do Parnaíba(2019-08-07) Ferreira, Thiago Augusto Bezerra; Vital, Helenice; ; ; Gomes, Moab Praxedes; ; Dominguez, José Maria Landim;The coastal zone are transitional environments, where continuous changes at different temporal and spatial scales occur, which are related to several processes such as oceanographic, fluvial, climatic and anthropogenic. Continuous monitoring of this environment provides essential information for understand the spatial distribution of erosive/depositional patterns, hence, its development. The main objective of this research was to investigate the Parnaiba River Delta’s (PRD) shoreline behavior, at short and intermediate time scale, between 1984 and 2017, through 12 Landsat satellite imagens and statistical software (Digital Shoreline Analisys System). At intermediate scale, the results showed that 52 % of PRD’s beaches are under shoreline retreat, while 48% exhibited progradation. At short intervals, shoreline variations are directly related to the climatic hydro influence in the drainage basin, specifically with the El Niño and La Niña effects. On both time scales, major erosion trend occurred away from Parnaiba River mouth and predominantly on the west side of the delta, while deposition, or stability, prevailed on the east side. Due to lower anthropogenic impacts, both on coastal zone and the drainage basin area, the natural factors, mainly river discharge and rainfall trends, are likely to be main driving forces of shoreline changes between 1984 and 2017.