The study examines the Ediacaran-Cambrian plutonic magmatism within the Rio Piranhas-Seridó (PSD) and São José do Campestre (JCD) Domains (NE Borborema Province, Brazil), with a focus on the radiogenic heat production (A) of granitoids. This magmatism encompasses a variety of batholiths, plutons, stocks, and dikes, with distinct petrographic and chemical features, grouped into six plutonic suites. The radiogenic heat production was investigated and compared with petrographic and chemical characteristics of the granitoids from the High-K Calc-Alkaline (porphyritic and equigranular) and Shoshonitic suites, encompassing syeno-monzogranites to monzodiorites, and gabbros/diorites, with metaluminous to peraluminous compositions and calc-alkaline to alkaline signatures. The high-K calc-alkaline porphyritic granites register higher A values (up to 11.7 µW/m³) due to high concentrations of Th and U, in contrast to the lower values in shoshonitic rocks (up to 3.5 µW/m³). There is a positive correlation between A, SiO₂, and the modified alkali-lime index (MALI), suggesting that more evolved and alkaline compositions favor higher heat generation. The mean Th/U ratio for all suites is 8.6, exceeding typical crustal values. The studied rocks were classified into low (LHP), medium (MHP), and high (HHP) heat production groups. The JCD samples mainly correspond to LHP and MHP, whereas those from the PSD include all categories, with HHP restricted to calc-alkaline granites and shoshonites limited to the LHP group. The spatial distribution of A and the concentrations of Th, U, and K indicate areas within the PSD with geothermal potential for further investigations.

Carbonate rocks constitute important reservoirs of mineral resources, however, they exhibit a high degree of anisotropy and heterogeneity, with various types of pores and scales that challenge both the industry and the scientific community. Digital petrophysical studies aim to obtain intrinsic rock parameters through the 3D rendering of X-ray microtomography images. The present study aims to classify pore types and estimate petrophysical parameters from the 3D rendering, segmentation, and numerical simulation of images of carbonate rocks from the Jandaíra Formation, Potiguar Basin, Rio Grande do Norte, Brazil. The images were acquired by X-ray microtomography, with resolution of 35 μm, and represent transverse slices of the rocks. For the treatment of slices, the ImageJ program was used. The segmentation of 3D pores was performed using the multi-Otsu method with the Simpleware ScanIP software. The segmented files were discretized and imported into the Comsol Multiphysics numerical simulator with coarse mesh density. The simulator adopts the finite element method (FEM) to perform its calculations. The simulated physics was configured to be a single-phase fluid in steady-state, laminar flow, with a density of 1000 kg/m3 and a viscosity of 0.001 Pa.s.

The differential pressure between the inlet and outlet of this fluid was established at 1 Pa. Comparing with literature and laboratory-obtained values, the digital results were satisfactory and consistent. Segmentation enabled the classification of well-developed stylolites and vugs among the samples. Petrophysical estimates ranged from 0.70% to 7.99% with effective porosity and simulated permeability ranged from 7.79 mD to 3000 mD. Regarding deep learning, the Alexnet model, with SGD criterion and MSE optimizer, exhibited the best performance.

This master's thesis explores the relevance of studies on rocks analogous to reservoirs, with a primary focus on the petrophysical permeability parameter. Traditional petrophysical techniques provide absolute values for this parameter but offer limited insights into the underlying reasons for these values. The absence of precise information necessitates the use of more advanced techniques for a systematic reservoir analysis. While Nuclear Magnetic Resonance proves effective in obtaining advanced reservoir information, its analytical models for permeability lack accuracy, particularly in heterogeneous reservoirs, revealing certain limitations. Filling this gap, this study aims to improve permeability predictions by employing machine learning models such as Random Forest, Gradient Boosting, and Multi-Layer Perceptron. The goal is to predict permeability based on patterns obtained through Nuclear Magnetic Resonance, compare them with analytical models, and identify the model that best suits the reservoir. It was observed that machine learning models provided more accurate predictions compared to analytical models.

Deltas, serving as significant hubs for agriculture, industry, and energy, are susceptible to coastal  erosion owing to anthropogenic pressures in both the drainage basins and the coastal zone. This study  investigates alterations in the shoreline of three northeastern Brazilian deltas (São Francisco, Parnaíba,  and Jequitinhonha) from the 1980s to 2021, correlating them with both human-induced and natural  impacts. Multispectral imagery was utilized to assess horizontal changes in the shoreline through the  DSAS software, providing insights into long-term trends across different decades. Additionally,  variations in the active coastal area were analyzed for the same periods. Furthermore, for the São  Francisco delta, sandbanks downstream of the Xingó dam were delineated using satellite imagery.  Hydro-climatic data from stations proximate to the coastal zone were also incorporated into the study. The data reveals that the Parnaíba Delta demonstrated a progradation rate at its mouth surpassing 20  m/year, resulting in sedimentary gains of 6 km² across the delta, encompassing 2.2 km² specifically at  the mouth. The most notable period of progradation occurred between 1991 and 2005, aligning with  heightened rainfall and fluviometric peaks in the lower river course. 

In contrast, the Jequitinhonha delta experienced predominant erosion processes at the mouth,  characterized by rates below 10 m/year and an increased delta mouth protrusion angle of 12° from  2005 to 2021. The limited correlation of the active coastal area (R² = 0.49) suggests that sediments  eroded at the mouth are transported, via bidirectional currents, to the delta's margins. Among the three deltas, the São Francisco delta exhibited pronounced erosion at the mouth, with  losses exceeding 20 m/year, reaching up to 50 m/year. The angle of the mouth increased by 13° during  the analyzed period, and there was a net loss of 6.2 km² of, with 2.6 km² attributed to the mouth alone.

Due to sparse human habitation along the coast, the construction of dams within approximately 100 km  of the coastal zone has emerged as a significant contributing factor to erosion processes in the  Jequitinhonha and São Francisco deltas. Prior to the construction of the Itapebi and Xingó dams, both  deltas exhibited relative stability in their coastlines. However, post-dam construction, Net Shoreline  Movement (NSM) data indicated a gradual increase in erosion at the mouths over time. Additionally,  these structures potentially retained sediments upstream of the dams, thereby reducing the annual and  monthly variability of the lower river courses of the Jequitinhonha and São Francisco, resulting in a  diminished capacity for riverbank erosion and sediment transport to the coastal area. For instance, within the São Francisco delta, spanning from 1984 to 2021, there was a reduction of  7.54 km² in the sandy banks downstream of the Xingó dam. This figure exceeds threefold the loss of  active coastal area observed across the entirety of the delta. Notably, this phenomenon did not occur in  the Parnaíba delta, as the Boa Esperança dam is situated 600 km away from the coastal zone. Climate change, alongside potential mining and dredging activities, may further alter the stability of  the Parnaíba Delta and exacerbate erosion processes in the Jequitinhonha and São Francisco Deltas.  Over the last two decades, northeastern Brazil has experienced a reduction of more than 30% in  rainfall. IPCC data suggests a projected 60 to 70% reduction in rainfall in this region by 2100.  Consequently, the capacity for river transport is expected to decrease significantly, thereby intensifying  erosion processes in both deltas.

The Furna Feia cave is the second largest cave in the state of Rio Grande do Norte, and it
was developed within the Cretaceous carbonates of the Jandaíra Formation. The aim of this
study was to analyze the geological indicators that affected the development of this karst
system, combining geological and geophysical data from surface and subsurface. Therefore,
a multidisciplinary approach was adopted, utilizing field visits, GPR, drone, LiDAR, gamma
rays, porosity, permeability, uniaxial compression strength, and petrography. The cave is
shallow, with 766m of linear development, linear meandering geometry, and its walls and
ceiling exhibit domes and pockets. The facies associations identified were tidal bars at the
base and top of the cave, intercalated with the lagoon facies association. Within this lagoon
interval, the rocks are intensely dolomitized. The tidal bars at the base indicate paleocurrent
to the northwest, and the tidal bars at the top of the section indicate northeast. LiDAR data
showed that the dolomitized interval is also the most dissolved, along which the cave exhibits
the greatest widening. This interval also showed a greater amount of fracturing in GPR data
and field analyses. Controversially, this interval presents the lowest values of porosity and
permeability in its matrix. Additionally, structural analyses also showed a tectonic influence on
the development of this karst system. The Poço Verde Fault, with a northwest direction,
affected the orientation of both the galleries and the pockets and domes found in the cave.
Therefore, we conclude that dolomitization exerted the greatest control on the formation of
the cave, as it provided the highest concentrations of fracturing and consequent horizontal
fluid percolation for the subsequent dissolution of carbonates. Tectonics, on the other hand,
guided this dissolution in preferential directions (northwest and northeast). These findings can
be extrapolated and used as guidelines in carbonate reservoirs affected by the same
process, indicating a dual porosity behavior for these rocks.

The Brazilian equatorial margin (BEM) is an oblique-transform segment with counterparts in the Gulf of Guinea on West Africa. Both margins are inherited from the Pangea breakup and hence opening of the Equatorial Atlantic Ocean. These areas have been studied as new exploratory frontiers and recently gained attention due to petroleum systems found in deep- and ultra-deep waters in both conjugate margins. The strike-slip Barreirinhas Basin, located at the central portion of the BEM, has counterparts with the oil and gas producers Ivory Coast and Tano basins. Nevertheless, no relevant reserves were identified on the Barreirinhas Basin yet, moreover due to the poor study in respect to the petroleum systems, particularly on deep-waters. This present study aims to identify cold seeps localized in shallow strata and associated with hydrocarbon migration, indicating possible hydrocarbon accumulations along the offshore Barreirinhas Basin. Investigation was made through conventional 2D seismic reflection in post-stack time migration with additional use of seismic attributes, including RMS amplitude, instantaneous amplitude, instantaneous frequency, and chaos. These seismic attributes are extensively used in the petroleum industry to reduce exploratory risks by optimizing the conventional seismic lines. The results comprise the identification of cold seeps, in shallow-strata, associated with hydrocarbon migration, including leaking faults, gas chimneys, pockmarks, hydrocarbon-derived diagenetic zone (HRDZ), bottom simulating reflectors (BSR), and deep-water mounds. Regional morphologic and stratigraphic structures constrain the zones of cold seep occurrences formed by fluid leakage and seepage, which indicate petroleum systems. In the eastern lower continental slope and continental rise, regional normal faults and gas chimneys controls cold seep formation. On the central to northern sectors of the continental rise and abyssal plain, several deep-water mounds are linked by large gas chimneys and faults. There are gravitational gliding systems on the western and central portion of the basin, where the extensional domain is characterized by normal faults, negative flower structures, and gas chimneys that produce cold seeps on the outer shelf and upper slope. These structural controls are related to the compressional domain of the lower continental slope and continental rise, where the decollement zone and series of faults and folds are correlated to pockmarks and deep-water mounds. Near to the western compressional domain, igneous intrusions control the development of leaking faults, gas chimneys, bright spots, and pockmarks. These hydrocarbon-derived structures, cold seeps, and pathways of fluid migration in deep-water indicate potential petroleum systems in the Aptian to Turonian-Oligocene tectono-sedimentary sequences in the central sector of the Brazilian Equatorial Margin. However, more refined techniques are needed to confirm the presence of active hydrocarbon seepage and/or storage. Likewise, the Barreirinhas Basin can be a vast field to the petroleum industry and scientific research, with the latter specially focusing in the nature of the HRDZs and deep-water mounds, endowed of great potential for the geobiology.

Detecting subsurface beach ridges covered by aeolian modern sediments is challenging through conventional methods such as aerial photogrammetry and satellite images. In this scenario, Ground Penetrating Radar (GPR) is the primary method for identifying and characterizing beach ridges. The integration of facies analysis and radarfacies characterization further enhances the accuracy of beach ridge and the sequence of prograde coasts interpretation. Combining geophysical techniques with traditional sedimentological analysis highlights the complex depositional processes associated with beach ridge formation and establishes a solid foundation for future research. A beach ridge is identified in GPR profiles following two criteria: the sigmoidal external geometry of these bedforms
and their internal radarfacies. The sigmoidal envelope of each beach ridge encompasses strata deposited in the backshore, foreshore, and shoreface settings. The comprehensive depositional model for beach ridges offers insights into their distribution, depositional architecture, sequence stratigraphy, internal structures, and the impact of sea-level fluctuations on beach ridge formation and preservation. Overall, this study significantly advances our understanding of beach ridge formations and their depositional architecture. It contributes to the field of coastal geology and offers practical insights for the understanding of coastal processes, which may be a valuable framework for studying similar landforms worldwide.

This study utilizes passive seismic interferometry, focused explicitly on calculating the auto-correlation function,on extracting reflections of P-waves centered on each receiver. Stacking these reflections allows for the construction of seismic sections at zero of sets. Typically, this technique uses data based on environmental noise or earthquakes. However, in this study, measurements taken during the hydraulic fracturing process in the vicinity of the Potiguar basin located in northeastern Brazil were used. Although this acquisition was not intended for a passive seismic interferometry experiment, an advantage was taken of its design and location concerning the fracturing point to evaluate the ability to construct seismic images from induced ambient noise. This geometry is composed of three main lines with three dif erent azimuth angles, which intersect precisely at the point of fracturing located at a depth greater than 400 meters. To extract the best body wave component from Green's function, we apply a novel variation to the commonly used processing flow. This includes the Gaussian smoothing filter, which allows a smoothed amplitude spectrum to be obtained. This spectrum may still be af ected by high-energy point events that need to be further treated, for which the whitening process is considered using the division between the natural spectrum of the data versus the smoothed spectrum. After applying the inverse Fourier transform to each trace obtained for each station, they are complemented to form the resulting seismic sections, which are compared to active source seismic lines acquired close to the study area and interpreted with available geological information. Seismic images were built in 2D and projected in 3D, taking advantage of the peculiar geometry arranged for monitoring the hydraulic fracturing process. This allowed analyzing the consistency between each of the acquired lines, also considering the point of intersection between them. Within this context, we can define a result of seismic sections that have well-defined reflectors of high resolution, continuity, and a satisfactory reproduction of the limits of the dif erent geological formations typical of the Potiguar basin, such as the Jandaira, Açu formation, and the basement top. Our work demonstrates the potential of passive seismic interferometry to generate high-resolution seismic images with highly ef icient processes, considering the low relative investment level, very low environmental impact, and high-quality results.Applying Seismic Noise Interferometry to extract high-resolution P-wave reflectivity from hydraulic fracturing data

In the extreme NE of the Borborema Province, within the tectonostructural context of the São José do Campestre (DJC) and Rio Piranhas-Seridó (DPS) domains, Ediacaran-Cambrian magmatism is responsible for generating igneous bodies constituting one of the main geological features. These are represented by different magmatic suites formed by various batholiths, plutons, stocks, and dikes. In this context, a range of studies, from a petrographic/textural and chemical (lithochemical and mineral chemistry) perspective, has been conducted for the six identified plutonic suites. However, for the Shoshonitic Suite, despite significant contributions in terms of mapping, petrography, lithochemistry, geochronology, and intensive crystallization parameters, there is a lack of integration of various bodies. Thus, there was an identified opportunity to integrate existing literature data with unpublished data, aiming to characterize the petrogenetic aspects of Shoshonitic magmatism in DJC and DPS. This is based on petrographic, lithochemical, and mineral chemistry data, including intensive crystallization parameters (P, T, and fO2). For the research development, twelve plutons were selected: Casserengue, Japi, Monte das Gameleiras, Poço Verde, Riachão, Serrinha, Acari, Quixaba, São João do Sabugi, Serra do Caramuru, Tapuio, and Totoró. Through the integration of compiled data, it was observed that rocks belonging to the Shoshonitic Suite in the DJC and DPS domains are transitional between calc-alkaline and alkaline or subalkaline rocks, with chemical peculiarities. These rocks are basic to intermediate, enriched in Fe2O3, MgO, CaO, TiO2, MnO, and K2O, all showing negative correlations in Harker-type variation diagrams, except for K2O, which correlates positively. The rocks of this suite are the oldest among the Ediacaran magmatism in DJC and DPS. Regarding intensive crystallization parameters, pressures were calculated based on empirical and experimental geobarometers of Al in hornblende. Initially, these rocks are relatively similar for DJC and DPS, with average pressures ranging between 4.1 kbar and 5.5 kbar, corresponding to crustal depths of 15 to 23 km. Average temperatures are also slightly different between the two domains, ranging from 911 to 1078°C, under conditions slightly reducing to slightly oxidizing. The estimation of oxygen fugacity conditions based on amphibole composition indicates predominantly high and subordinately intermediate conditions, typical for this rock type.

Fault zones accommodate deformation in a complex pattern, presenting themselves with different geometries, types of secondary structures, and changing the petrophysical parameters of host rocks. From a perspective of exploration of siliciclastic hydrocarbon reservoirs, understanding the complexity of fault zones has become fundamental, since these structures alter rock volumes, thus influencing fluid flow. The challenge of understanding these structures requires the use of conventional methodologies, providing relationships with the structural framework of the basin, as well as understanding the deformation of a fault zone from the outcrop scale, where it is possible to observe secondary structures such as deformation bands. In this research, fault zones in the Rio do Peixe Basin were investigated at the outcrop scale, understanding the mechanical-stratigraphic influence of deformation bands, and fault detection and characterization were also performed automatically using reflection seismic data. For this, structural, sedimentological and petrophysical data were combined to analyze mechanically the rock layers, and to characterize the deformation generated by deformation bands. Also, seismic data were used for automatic fault detection through seismic attributes and deep learning. Our results show the mechanical-stratigraphic influence of deformation bands in a fault zone that indicate the same regional trend of NE-SW, E-W and NW-SE direction, generating changes evidenced by our models in petrophysical parameters such as porosity, permeability, Young's modulus and Poisson's ratio. The deformation bands cross the sedimentary layers without being conditioned to their thickness, varying structural parameters such as frequency, dip, geometry and thickness of the bands. Our results also demonstrate the comparison between seismic attributes and deep learning (DNN), in which DNN is more successful in detecting faults, identifying their subsidiary segments with more strikes variation and number of minor faults. Seismic attributes are shown to be conditional on noise in the seismic data. Furthermore, we interpreted and mapped a new fault, which is aligned parallel to Fault Malta of E-W direction, with a central negative flower structure.

Geophysical methods aim at obtaining information about the subsurface rocks and fluids. To achieve this goal, different methodologies are employed to more accurately determine both the geometry and physical properties of the Earth’s strata at depth. Seismological methods recover structural and velocity information in the subsurface, while MT techniques are powerful tools to characterize the saturation of fluids, such as hydrocarbons or saline water, in subsurface rocks. Seismological or magnetotelluric (MT) measurements provide incomplete information when used independently. Combined, these techniques have the potential to considerably improve the imaging of structural features at depth. This paper evaluates the performance of joint analysis of seismological and magnetotelluric data for determination of subsurface structure beneath the Borborema Province and northern São Francisco Craton, using data collected along a N-S profile centered at the Araripe Basin.

First, resistivity and S-wave velocity models were obtained through independent inversions. The velocity models were obtained through simultaneous inversion of receiver functions and dispersion curves, and revealed the presence of a layer with high velocity (4.1-4.3 km/s) below the Araripe Basin - which was interpreted as a mafic layer in the lower crust - and a decrease in velocity (< 4.3 km/s) below 120 km depth. The resistivity models were taken from an existing 3D inversion of apparent resistivity and phase curves, noting the presence of high conductivity ( 25 Ωm ) in the mantle (120 km) beneath the basin. This conductive anomaly was interpreted as material enriched with small amounts of magma derived from Mesozoic rifting processes. The joint interpretation of the results thus evidences a thinning of the lithosphere beneath the Araripe Basin, contributing to improve our understanding of the tectonic inversion processes of this basin. 

The performance of the joint inversion of magnetotelluric and seismological data was also investigated. The joint inversion used the same receiver functions, phase and apparent resistivity curves as the independent inversions; however, a brand-new mean phasevelocity dispersion curve had to be utilized. The inversion assumes a common seismic and resistivity structure (1D), represented by a set of layers above a half-space. Furthermore, the inversion is performed using a multi-objective genetic algorithm (GA) that efficiently exploits the parameter space. Our results demonstrate that, in spite of considerable geological complexity, it is possible to determine structurally consistent velocity and resistivity structures beneath the Borborema Province and the São Francisco Craton. The inverse (1D) models do not allowed to develop empirical relationships between resistivity and S-wave seismic velocity at crustal or mantle depths, but they were able to image an electric Moho beneath most locations within the study region.

Terrain modeling, feature extraction, and automated classification are being applied in the subsurface to understand the forces that shape the seafloor. However, marine geomorphometry still requires further scientific effort due to the dynamic nature of the marine environment and the challenges of data acquisition. A geomorphometric analysis of the Jequitinhonha basin in northeastern Brazil was performed using satellite, nautical chart, and multibeam bathymetry data. The results obtained allowed the identification of new geomorphic features in this portion of the continental shelf, including six submarine canyon heads, a new direction of erosion of Belmonte Canyon on the continental shelf, a new unfilled incised valley, and paleochannels. Coral reefs, a paleo-spit, and a paleo-lagoon were also mapped. The positions and orientations of these paleodraineges systems indicate a significant change in fluvial flows in the narrow continental shelf of this region, transporting large amounts of sediments to the abyssal zone. This study highlights the importance of marine geomorphometry in identifying potential hazards to navigation and exploring natural resources. It also emphasizes the need for continued research to improve our understanding of the seafloor's morphology and the dynamic nature of the marine environment.

Along the Brazilian Equatorial Margin (BEM), a set of sedimentary basins have evolved from Neobarremian to Albian. This region has aroused significant interest due to recent discoveries of hydrocarbon reserves on the continental margins of Ghana, in Africa, and the Guianas/Suriname, in South America. However, the absence of exposures of the Aptian-Albian rift and the overlap of brittle structures related to this event with older and/or younger structures related to the Neocomian-Barremian rift and post-Campanian intraplate deformation hinder the correlation of surface-mapped structures with transtractive/transpressive tectonic events related to the evolution of the Equatorial Atlantic. In this work, we carried out an analysis of the orientation and distribution of brittle lineaments in the onshore Brazilian and African equatorial margins. In more detail, and also considering field data, trends associated with surface brittle lineaments were compared with magnetic lineaments in the Potiguar, São Luís, Bragança-Viseu, Grajaú, and Barreirinhas basins. The results indicate continental influence of Albian tectonics reached the southern portion of the Grajaú Basin, suggesting dextral transtension of the BEM during the Albian and control of the inheritance of Brazilian shear zones from the Gurupi and Araguaia belts, Borborema Province, and the Transbrasiliano Lineament in the development and reactivation of brittle structures in various stages of the BEM evolution. Furthermore, a study of the deep crustal architecture in the offshore área of the BEM was conducted, integrating gravity, magnetic, and 2D seismic data. The BEM was divided into four domains: proximal (PD), neck zone (NZ), ocean-continent transition (OCT), and oceanic crust (OC). These domains exhibit a predominance of NW-SE normal and oblique-slip faults from Aptian to Albian, associated with E-W strike-slip and oblique-slip faults, as well as NE-SW folds and thrusts. Ocean-continent transitions can vary from gradual to abrupt, depending on the location and predominant structural style in each segment of the margin. The defined boundaries provided a good fit between the continental crusts of the BEM and the African Equatorial Margin (AEM) during the Cenomanian. This study contributes to a better understanding of basin formation mechanisms in the BEM, opening perspectives for exploring its petroleum potential in deep and ultra-deep waters.

The Ceará Basin is located at the east portion of the Brazilian Equatorial Margin, and it covers, geographically, the states of Ceará, Piauí and part of Maranhão. The basin is subdivided from west to east into four sub-basins: Piauí-Camocim, Acaraú, Icaraí and Mundaú, the latter being the study region. The Mundaú Sub-Basin covers an area of approximately 12,000 km2 and it has three tectonosedimentary stages: Rift, Post-Rift and Drift. The section that includes the Lower Cretaceous, Paleocene and Eocene is within the Drift stage, which is lithostratigraphically represented by the Ubarana, Tibau and Guamaré formations. That interval has oil potential indicated by the Ubarana – Upper Cretaceous play, characterized by turbidite reservoirs, similar to important discoveries at the African Margin, such as the Jubilee field, and at the Equatorial Margin in offshore fields of Guyana and Suriname. For this study, concepts of low and high resolution stratigraphic analysis were used in data from eight exploration wells and ten 2D seismic lines, located from the most proximal portions, in shallow waters, to the deep water region. The analysis of the wells allowed the characterization of lithofacies and transgression/regression cycles which, together with seismic analysis, through the recognition of reflector terminations, seismic facies and unconformities, resulted in the individualization of six depositional sequences. Furthermore, this analysis allowed the identification of turbidite plays in deep waters, that are important in the context of the Brazilian Equatorial Margin and the African conjugate, as analogues to reservoirs of the same age in producing basins on the Eastern Margin.

The Ediacaran to Cambrian magmatism in the Rio Grande do Norte Domain, in the extreme NE of the Borborema Province, is represented by six suites defined by chemical, mineralogical and petrographic criteria: Shoshonitic, Porphyritic high-K Calc-alkaline, Equigranular high K Calc-alkaline, Calc-alkaline, Alkaline and Charnockitic Alkaline. However, as some divergences were observed between the results of a specific body classified in the
alkaline suite, the Stock Flores, it was analyzed separately. This work presents as main object the study of Rare Earth Element patterns using a new methodology for applying the patterns in petrogenetic problems having the Ediacaran/Cambrian magmatism of the Rio Grande do Norte Domain as a sample universe. Thus, the use of the lambda method to obtain the shape coefficients (i.e. λ0, λ1, λ2, λ3). The mean values for the shape coefficients (λ0/λ1/λ2/λ3 notation) observed are for Shoshonitic (5.36/8.68/108.65/-1438.32), Porphyritic high-K Calc- alkaline (5 .34/11.83/141.35/-1464.81), Equigranular high K Calc-alkaline (5.43/9.29/152.15/-1486.88), Calc-alkaline (4.77 /5.44/149.65/-1383.71), Alkaline (3.85/3.49/174.37/-1282.47), Alkaline-Flores (5.63/4.12/152.31 /-1166.31) and Charnockitic Alkaline (5.60/9.98/128.10/-1638.25). The results show a strong influence on the fractionation of feldspars on the observed ETR patterns, mainly regarding to the Eu anomalies observed using λ0 as a plagioclase fractionation marker. Other minerals such as garnets, clino and orthopyroxenes may have an influence on low values of λ1 and high values of λ3 while minerals that partition alkali influence high values of λ2. The Sm-Nd results point to negative εNd values, indicating an enriched source. The TDM model ages indicate age variations between the Paleoproterozoic (Staterian) and the Mesoarchean, which shows a possible age for the sources of these rocks. Furthermore, the T2DM model ages present a variation between Paleoproterozoic and Paleoarchean. Furthermore, the interpretation is that the shoshonitic suite has as its source the enriched mantle associated with a subduction zone related to the Transamazonian/Eburnian event (ca. 2.15 Ga), while the rocks of the other suites are sourced from the relative continental crust to the Paleoproterozoic to Archean gneiss-migmatitic basement.

This study integrates geological/geophysical, petrographic/diagenetic, and petrophysical data to individualize rocks with different flow capacities producing oil in a field in the Potiguar Basin, NE, Brazil. The work used information from more than 800 vertical wells, 19 of which have rock data and petrophysical analysis. Seven wells provided most of the data for the present study because of the greater thickness of cores recovered. Implementing the multiscale approach that we presented was essential in understanding the geological aspects that influence the reservoir production capacity. At the micro scale, for example, through the study of thin sections, it was possible to identify and recognize clay minerals that occur may obstruct pore throats and, consequently, affect the permeability and productivity of the rocks. At the meso scale, the study of cores in different portions of the field allowed us to characterize the depositional systems in the area and identify factors that influence the entry of oil into the reservoir. Finally, through the correlation of rock vs. profile at the macro scale, we estimated the distribution of the flow units defined for the other wells, thus allowing the construction of maps and petrofacies sections with geological and dynamic significance. At this last scale, we visualize the geometry of the sedimentary deposits and their heterogeneities, whose understanding directly influences the planning and development of an accumulation (for example, in the definition of the production wells grid and water or steam injection in case of application of secondary recovery methods). Additionally, we developed a methodology to quantify the production capacity of the rocks from a reservoir quality index (RQI) that we validated with field production data.

Digital Outcrop Models (DOMs) are visual representations of geological sites in a virtual environment. DOMs are constantly evolving and widely used tools for geological investigations. However, in contrast with their broad applications, the full potential of DOMs is still underexplored in terms of their integration with other data. We present an integrative approach by combining a DOM with stratigraphic, petrophysical, fracture distribution and karst dissolution information into a single 3D georeferenced digital model. Fracture aperture enlargement due to karstic dissolution are implemented on a Discrete Fracture Network (DFN) to generate a Discrete Fracture and Karst Network (DFKN), where it is possible to compose different karstification scenarios. The used DOM is based on photogrammetric data obtained inside the Access 1 of the Cristal Cave. This cave developed in Mesoproterozoic carbonate rocks of the Caboclo Formation, in the Chapada Diamantina Group, São Francisco Craton, Northeastern Brazil, and has been used as a structural and diagenetic outcrop analogue for the Brazilian pre-salt carbonate reservoirs. The described Integrative Model combines both deterministic (stratigraphy and petrophysics) and stochastic (DFN and DFKN) elements. The framework of the Integrative Model reproduces the stratigraphy of the Access 1 as 22 parallel layers, which were populated with measurements of porosity, permeability and uniaxial compressive strength. Resorting to a stochastic approach, we obtained a 3D DFN by solving the stereology inverse problem, where statistical measurements of the fracture traces (power law and P 21 persistences) on the walls and ceiling of the cave are honored. Petrophysical parameters of the Integrative Model can be easily changed. Also, it is possible to modify the power law that relates aperture and fracture length to implement different karstification stages of the fracture apertures. As a result, different scenarios of primary and secondary porosities can be easily composed, which can be used in fluid flow simulations, thus facilitating the understanding of the multiple factors affecting the behavior of carbonate reservoirs.

A-type granites are typically characterized by their alkaline trend, high concentrations of HFSE, high values for Ga/Al and HF/H2O ratios, and are mostly associated with post-collisional extensional and anorogenic environments. Over the last few years, however, a series of works have demonstrated that these rocks are much more complex both in terms of their geochemistry, associated tectonic environments and petrogenetic processes involved. In Brazil, A-type granites are described both in Archean to Paleo-Mesoproterozoic cratonic areas and in Neoproterozoic mobile belts, with several occurrences associated with important mineral deposits (Sn, In, W, among others). Many of these occurrences are described and interpreted in a local or regional context, so that an integrated and comparative analysis on a broader scale is still absent in the literature. In this context, this dissertation presents the results of data-driven discovery, by applying data science techniques to manipulate, process and analyze (with the aid of unsupervised machine learning with the K-means algorithm) an extensive database of rock-total geochemical data (>1,900 samples) of A-type granitoids from Brazil in various geotectonic contexts and of various ages. The results show that A-type magmatism in Brazil can be separated into three subgroups named A1, A2 and A3, with distinct geochemical (and partly petrographic) characteristics. The first two show correspondence with the A1 and A2 subtypes already established in the literature, while the third defines a new subgroup, characterized by less evolved lithotypes. These subgroups are individualized in several binary and ternary diagrams proposed in this work from combinations of chemical variables (major and trace elements) and normative minerals. The A1 subgroup encompasses alkali to alkali-alkalic rocks, of peralkaline to metalluminous character. The A2 granites are alkali to calcium-alkaline, peraluminous to weakly metalluminous; while the A3 subgroup includes alkali, alkali-calcic, calcium-alkaline to calcic, metalluminous to peraluminous (to a lesser extent) rocks. Although they do not have preferences for a particular tectonic context or range of occurrence over geologic time, the A1, A2 and A3 subgroups can occur together in the same body, with seven possible combinations, suggesting that they may represent different facies related to each other by magmatic differentiation processes. The association of the subgroups with a specific geotectonic context is not always direct. However, in general terms, plutons formed exclusively from A1-type granites relate more strongly to anorogenic to post-orogenic environments, whereas A2 and A3 subgroups are linked to syn- and post-collisional to late-collisional contexts.

The Parnaíba River Delta, located in northeastern Brazil, is one of the few examples of a deltaic depositional system that still has its characteristics well preserved, which makes it increasingly the target of scientific research in the most diverse areas. The present work aimed to identify changes in the depositional environment, based on the vertical analysis of sediments. Vibracores were collected in old mangrove forest, in active zones of tidal channels, and in supratidal swamp. The study included sediment analysis associated with petrophysics (Gamma Ray Spectrometry), as well as dating by the radiocarbon method using the Mass Spectrometry Accelerator technique. In a first phase, the gamma-ray spectral analysis and the photographic record of the cores were carried out, followed by the stratigraphic description, as well as the identification and selection of material for dating (e.g. shells, wood). Subsequently, the cores were sampled at regular intervals, every 4 cm, for granulometric, compositional (organic matter, and calcium carbonate quantification) and mineralogical analyses. The results obtained showed mineralogical variations, indicating changes in sedimentary origin. The gamma-spectrometric data tend to show higher values with the decrease of the grain and associated to the sedimentological, stratigraphic and mineralogical data improves a better interpretation of the depositional history. The contents of organic matter and calcium carbonate, in general, presented variations related to the grain size, with fine sediments presenting higher contents of organic matter, while carbonate is related to the presence of shells. Datings showed ages ranging from 4057± 22 BP to more recent ages (1950 AD). The integration and joint analysis of the data allowed a better interpretation of the late Holocene evolution of the current system of tidal channels on the western and eastern margins of the Parnaíba river delta.

This dissertation investigates the tectonic role of the Precambrian shear zones and the Romanche Fracture Zone (RFZ) in forming the central part of the Brazilian Equatorial Margin. To this aim, gravimetric, magnetic, elevation, seismic and well data were compiled, processed and integrated. The separation between the South American and African continents, in the Lower Cretaceous, was strongly conditioned by the Precambrian structural fabric of amalgamated crustal blocks along extensive shear zones during the Brasiliano Cycle (720-540 Ma). The reactivations of these continental-scale shear zones occurred mainly where there was high mechanical contrast between Precambrian terrains, compartmentalizing the continental margins on both sides of the Equatorial Atlantic. These shear zones arrest at the RFZ, where the continent-ocean crustal boundary occurs. The reactivated faults and folds are compatible with an initially extensional stress field during rifting until the Aptian. This stress field inverted to strike-slip after the main breakup phase, with the direction of maximum compression varying until the Present. In this context, the RFZ divides this sector of the Equatorial Margin into one E-W-transform and two NW-SE-oblique divergent segments. Gravimetric models along regional seismic sections reveal distinct crustal behaviors for each segment: south of the RFZ, a divergent margin with a crustal stretch of ~90 km; along the RFZ, a transforming margin with little extended continental crust (~30 km); and to the north of the RFZ, another divergent segment shows a hyperextended continental crust up to 160 km long on the continental shelf. The Moho discontinuity and the internal geometry of the sedimentary basins were also modeled, completing the lithospheric characterization of the Equatorial Margin. The basins South of RFZ are thicker than those to the North because this structure acted as a barrier to the deposition of continental sediments in the oceanic regions. The boundary between continental and oceanic crusts identified in the present work is also consistent with previous studies. However, it diverges from these studies north of the RFZ due to the hyperextended continental crust described here.

Kartisification processes in carbonate reservoirs are well defined in the literature and relevant for oil and gas exploration. However, the development of mixed-carbonate-siliciclastic reservoirs can sometimes be difficult to understand. The studied caves presented in this work comprise two main approaches: stratigraphic and structural. The main objective is to understand the behavior of a conduit-seal system in a mixed-carbonate-siliciclastic plataform in the Lapinha and Paixão caves, located at Una-Utinga Basin, Bahia, Northeast Brazil. The study is based on micro to macro scale analyses, through Light Detection and Ranging (LiDAR) surveys, Unmanned Aerial Vehicle (UAV) images, stratigraphic profiles, gamma spectrometry, Uniaxial Compressive Strength (UCS) using Schmidt hammer, structural field mapping and laboratory data analysis, petrographic and
petrophysical analyses. The stratigraphic results comprise the definition of three sedimentary facies described in a vertical columnar section of 22 m in Lapinha and 10 m in Paixão, as well as in thin sections. At the bottom of sections, the lime mudstone facies (Lm) comprises 10% of siliciclastic sediments, which characterizes Lm as the most soluble facies, responsible for the development of most cave passages. Heterogeneous calcarenite facies with carbonate and siliciclastic intercalations may present a conduit or seal behavior, depending on siliciclastic sediments variation (ca. 30-50%). The mixed limestone facies with siliciclastic sediments, about 50% of siliciclastic content, can be characterized as a sealing facies due intense chemical compaction. In addition to the stratigraphic control, it was possible to identify in these caves a structural control, based on quantitative analysis, associated with stratigraphic data. The conduit facies (Lm and/or CaLm) present great density and intensity of fractures indexes, while the sealing facies (LmTs), the opposite. In conclusion, siliciclastic sediments along the described sedimantary facies controls karstification processes at different scales in a mixed carbonate-siliclastic platforms. Thus, Lapinha and Paixão caves can potentially be analogues of mixed carbonate-siliciclastic reservoirs, using the stratigraphic and structural patterns described in the present work. The conduit-seal system in a mixed carbonate-siliciclastic platform may be interesting for characterization of these mixed reservoirs and for the prediction of oil and gas.

The recharge of unconfined urban aquifers is substantially affected by high rates of soil sealing, while, occasionally, it may present additional components to those from rainwater infiltration.  In this case, infiltrations caused by leaks in sewage and water supply networks can represent significant contributions to these recharge rates. This situation is common in some areas of Northeast Brazil, especially in places with high population density and deficiencies in wastewater collection and supply networks. In this last aspect, it is not uncommon to have the contamination of urban aquifers by nitrate resulting from the infiltration of untreated wastewater. This research aimed to evaluate the effects of a variable recharge resulting from land use and occupation, as well as artificial contributions, in the Barreiras Aquifer, of a predominantly unconfined hydraulic character, in the city of Natal-RN. Additionally, we conducted simulations about the prospects of natural purification of waters with high nitrate contents, previously characterised by different renewal times associated with the changes in saturated zones due to decreases in recharge rates. The methodology used was based on the elaboration of numerical models and scenario analysis, emphasising the variations of artificial recharges resulting from wastewater infiltration and losses by the public supply network. Thus, the total recharge rates were calculated by individualizing areas with higher and lower population density, with subsequent simulations of different natural and artificial contributions. The results demonstrate significant variations in the potentiometric surface of up to 15 meters in several areas presented in the critical scenario, which considered the removal of artificial recharge and inversions of the groundwater flow. In this context, the saturated zones showed a variation of about 44 million m3 between the current and critical scenarios, associated with the suppression of 100% of the contribution from losses by the supply network and wastewater infiltration. In terms of prospects for natural purification of waters with high nitrate contents, from the analysis of renewal times and based on the variations of saturated zones calculated in the numerical models, values ranging from 6.5 to 12.9 years were obtained, this time being longer considering the most critical scenario reported in terms of recharge. The results presented here may contribute to the management of shallow aquifers in similar scenarios, especially regarding urbanization rates and efficiency in supply and sewage networks.

We evaluated the impact of karst dissolution on the permo-porous system of carbonate rocks, using field data obtained from outcrops of the Jandaíra Formation (Potiguar Basin). The karst system of this formation has excellent exposures, which allow the study of karst features both in vertical and horizontal planes. The integrated and multidisciplinary approach of this thesis was carried out in two stages. The first stage was predominantly two-dimensional (2D), in which we used scanlines and aerial images of Unmanned Aerial Vehicles to characterize
networks of karstified subvertical fractures. In this stage, we show that the process of fractures enlargement by karstic dissolution modifies the statistical relationships between fracture length and aperture. For early stages of karst dissolution, the length and aperture values follow approximately the classical power law distribution typical of mechanical fractures. However, as karstification progresses, fracture aperture tends to remain constant, regardless of its length. Thus, by adapting the aperture-length curve, according to the known stage of karst dissolution, it is possible to build discrete fracture models that include the effects of karstic dissolution. We call the resulting model DFKN (Discrete Fracture and Karst Network). We also show that fracture enlargement can increase the transmissivity of a karstified fracture network by up to five orders of magnitude, without changing its connectivity. The second stage of the research consists of a three-dimensional (3D) analysis of fracture networks, lithostratigraphic interfaces and karst features, based on the joint interpretation of Ground Penetrating Radar (GPR) cubes, core logs, porosity, permeability and total radiation profiles, images of borehole walls and thin sections. In this stage we verified that GPR signal attenuation zones are related to secondary alterations of carbonate rocks, which are caused by fracturing, fracture and pore enlargement, as well as stylolite dissolution. Such secondary alterations significantly increase the porosity and permeability of rocks. Fractures are the main pathways for fluid percolation, contributing to the evolution of karstification processes, especially in layers with higher primary porosity/permeability. On the other hand, layers with low primary porosity/permeability, but with
a high concentration of stylolites, can also develop zones of high permeability due to the interconnection of dissolved stylolites. The attenuation/dissolution zones can compose  connected volumes of high permeability and generally have tabular geometry, because they are limited by Tese de Doutorado – Lopes, J.A.G., 2022 PPGG – UFRN ix subvertical fractures and subhorizontal stratigraphic interfaces. At the reservoir scale, these tabular bodies may constitute super-k layers. In a unified view, our results contribute to a better understanding of the three-dimensional permo-porous system of fractured and karstified carbonate reservoirs.

Salt tectonics concerned with the geometries and processes associated with the presence of significant salt thicknesses within stratigraphic sequence. Salt behaves like a viscous fluid over geological time scales and, therefore, it may flow due to lateral differences in thickness and density of the supra-salt layers. This influences the structural evolution of sedimentary basins, and related structures are remarkably important for the exploration of mineral resources, oil and gas, as well as for energy storage such as gas in salt caverns (e.g. hydrogen and compressed air), CO₂ storage, and geothermal energy. Therefore, understanding the processes involved in salt tectonics has important scientific, economic, and social implications. In this regard, recent advances in analog modeling have been contributing to the hydrocarbon exploration and production industry associated with salt tectonics as one of the most powerful and visual tools for understanding 3D and 4D structural evolution of sedimentary basins. Knowledge of the model setup and combined with serial sections allows for the identification and understanding of structural processes within basins as well as providing possible geometries of poorly imaged structural geometries in seismic data. This thesis investigates the impacts of lateral and vertical salt flow on the supra-salt tectono-stratigraphic architecture developed in the realm of extensional basins as well as the origin and evolution of salt structures and supra-salt deformation in response to base-salt relief during gravity gliding in Atlantic-type salt basins formed in passive margin settings. To achieve this, the thesis uses a wealth of analog models in different settings of passive margins and continental rifts. This detailed and incremental approach allows for greater confidence in interpreting complex salt-related geometries and kinematics, improving their understanding. Although we do not address our models to specific salt basins, the structural processes and salt-related geometries modeled are also comparable and relevant to many other salt-bearing rifted margins (e.g., Gulf of Mexico, West Africa, East Brazil).

Single-channel seismic data are still a challenge to apply fundamental processing techniques such as deconvolution and migration. This study proposes a workflow processing for high-resolution seismic-reflection data regarding problems of   wavelet phase, low signal/noise ratio of raw data, random noise, transmission loss, static variations, and multiples, which restrict the geological information of shallow marine strata. The data were acquired using an Applied Acoustics Squid2000 sparker system, operating up to 2500J, with a frequency range of 100-1200Hz. The survey was carried out in the inner shelf of Bahia in front of the Jequitinhonha delta and aimed to investigate Quaternary deposits and stratigraphic structures. The processing explores fundamentally predictive deconvolution and Kirchhoff migration, and then applies techniques of static correction, band-pass frequency, gain, and average filters as secondary techniques. Deconvolution removed random and high-frequency noises and broadened the frequency spectrum of the data. Kirchhoff migration collapsed the diffraction hyperbolas, enhanced coherency, and continuity of reflectors along with the data, and repositioned dip reflectors to their real position. Application of static correction combined with bandpass fitter and average filters smoothed the undulating seabed reflector and subsurface reflectors. The results confirmed the efficiency of the processing workflow proposed here by removing random and high-frequency noises, correcting static variations, slightly attenuating the seabed multiple, moving reflectors to their real position, and providing a high signal/noise ratio image that better represents the subsurface of the southern Bahia continental shelf

The stresses that led to the opening of the South Atlantic were responsible for intracontinental extension and, consequently, for the formation of a number of aborted rift basins in Northeastern  Brazil. Extension began in the Neo-Jurassic, with the formation of an Afro-Brazilian depression south of the Patos Lineament, and continued in the Eoberriasian with rifting along two NS-trending deformation axes: Recôncavo-Tucano-Jatobá (RTJ) and Gabon-Sergipe-Alagoas (GSA). Rifting initiated north of the Pernambuco Lineament during the Neoberriasian – Eobarremian, later migrating to the West along the NE-SW Cariri-Potiguar (CP) trend. In the Neobarremian, approximately coinciding with the opening of the Equatorial Atlantic, rifting was aborted along the RTJ and CP axes and continued along the GSA trend, eventually resulting in the separation of the continents. The magmatic activity on the Brazilian continental margin seems to have been restricted to the north of the Patos Lineament, as represented by the dykes of the Rio Ceará-Mirim. The geological history of the continental rifting process in NE Brazil indicates the influence of different types of extensional stresses in the rifting styles of each sub-basin. In order to better understand the influence of these stresses on possible rifting models, 11 seismographic stations were installed in and around the RTJ rift in October 2018. The installation was funded by the national oil company Petrobrás and included both short-period and broadband stations. In addition, 10 more stations from the Rede Sismográfica do Nordeste (RSISNE) that were close to the study area were utilized. In this work, measurements of crustal thickness and Vp/Vs ratio obtained from the  joint analysis of receiver functions and surface wave dispersion, aided with the H-k stacking technique, are reported. The results show that the crust is 40 km thick below the Recôncavo and Tucano sub-basins and that it contains a thick layer (5-8 km) of high-velocity material (Vs > 4.0 km/s) below 35 km depth. These observations contrast with the structure immediately to the West (São Francisco Craton) and East (Borborema Province) of the basin, for which the crustal thicknesses are in the order of 44 km and 36 km, respectively, the lower crustal velocities are below 4.0 km/s, and local instances of crust as thin as 31 km are observed. Thus, we propose, according to the 'flexural cantilever' model, that the high- velocity layer that forms the lower crust of the basin resulted from mafic underplating after stretching and thinning during the syn-rift phase, restoring crustal thickness to pre-rift phase values (or greater) and providing the necessary buoyancy to initiate regional uplift. Furthermore, although not generalized, cases of thin crust along the footwall may be related to ‘rift flank’ erosion. We therefore conclude that, regardless of the mode of extension in the upper crust, our results favor basin formation models that involve the extension of the lower crust by pure shear

The S-SE region of Brazil, between the states of São Paulo and Santa Catarina, is marked by the occurrence of an intense Neoproterozoic volcano-plutonic activity, formed during the post-collisional stages of the Brasiliano orogeny.  The rocks are predominantly acidic, have chemical signatures of type-A granites and rhyolites and form several granitic and syenitic plutons (Graciosa Province), as well as effusive and explosive volcanic sequences in contemporary volcano-sedimentary basins. Additionally, the acidic volcanics in these basins are commonly part of a bimodal volcanism, with scarcity of intermediate lithotypes. Among these occurrences, the Morro Redondo Complex (PR-SC) is particularly interesting because it encompasses two type-A granitic plutons with contrasting geochemical affinities (peralkaline and peraluminous), along with comagmatic acidic and basic volcanics and subvolcanics. This work presents an integrated study of the Morro Redondo volcanic rocks based on (1) petrographic, (2) magnetic susceptibility, (3) lithochemical, (4) geochronological (zircon U-Pb) and (5) isotopic (zircon Hf-O) data. The results show that the basic volcanics and subvolcanics correspond to alkali-basalts and microgabbro/microdiorites with pigeonite/augite and andesine/labradorite and high magnetic susceptibility. On the other hand, the acidic rocks are predominantly alkali-feldspar rhyolites and granophyres with high SiO2 contents (>70 wt.%) and low magnetic susceptibilities. Two subgroups of rhyolites have been identified: (1) aluminous rhyolites, with biotite ± hornblende and metaluminous to peraluminous affinity, compositionally equivalent to the Quiriri granites; and (2) alkaline rhyolites, with sodic amphiboles and clinopyroxenes and metaluminous to peralkaline affinities (comendites), chemically similar to the Papanduva granites. In-situ zircon U-Pb dating (LA-ICP-MS) of an aluminous rhyolite indicate crystallization ages around 585±5 Ma that overlap within error with the ages of the Morro Redondo granites (578±3 to 580±5 Ma), as well as with the ages of volcanic episodes in volcano-sedimentary basins of S-SE Brazil. Additionally, zircon Hf-O isotopic signatures for this rhyolite indicate εHf values between -23.6 and -16.7 (with TDM model ages between 2.34 and 2.72 Ga) and δ18O = 5.0±0.1‰. The petrogenetic model proposed for the origin of the Morro Redondo volcanics starts with the partial melting (~13%) of an enriched mantle (EM-1 type) in an extensional post-collisional environment, with the production of basaltic magmas. These in turn would have promoted the partial fusion of the basement rocks (Luiz Alves Microplate) generating A-type magmas that ascended to shallow crustal levels, evolving by fractional crystallization (45-52%) to compositions akin to the aluminous granites of the Quiriri Pluton. From this "reservoir", subsequent processes of fractional crystallization (30-50%) mainly of alkali feldspar, gave rise to more peralkaline compositions (Papanduva Pluton). Finally, rhyolites were extracted from these crystalline mushs, ascending to the surface as dykes.

The cities on the east coast of the Rio Grande do Norte State are primarily supplied by the Barreiras Aquifer, which has a predominantly unconfined hydraulic character. However, the lack of reliable data about wells hinders the identification of more promising areas for future well locations, especially outside urban perimeters. In this context, the present research was carried out in an area in the lower course of Maxaranguape River-RN, aiming to identify the most promising subareas for the location of wells and estimates of hydraulic transmissivities of the Barreiras Aquifer based on geoelectric data. Thus, we adopted the methodology of the transverse electrical resistance (RT) parameter methodology through inverse models of vertical electrical soundings-VES, considering a previous geoelectrical calibration conducted adjacent to local research well with a defined lithological profile. The estimates of hydraulic transmissivities also resulted from the calibration between the transverse electrical resistance value and hydraulic parameters from the aquifer test in the referred well. Additionally, we conducted dependence degree analysis (linear regression - R²) between transverse electrical resistance (RT) values with the resistivity
and the saturated zone thickness parameters in order to identify a possible local predominance of one or another of these parameters in the definition of areas with the most significant hydrogeological potential.
The results obtained show a band in the center of the area with an NW - SE orientation and transverse electrical resistance values greater than 25,000 Ohm.m², associated with thicker sectors and/or average resistivities of the saturated zone. Thus, this subarea is the most promising in terms of hydrogeological potential. The mean thickness of the saturated zone showed values above 56m in the central and northwestern portions of the area. In contrast, the mean resistivity of the saturated zone showed values above 990Ωm in the extreme southwest and the central region. In this respect, analyzes based on linear regression demonstrate that average electrical resistivity exerts more significant influence on the transverse electrical resistance parameter in the study area, exhibiting a correlation factor R² of 0.88, in detriment of an R² of 0.39 of the ratio between saturated thickness and transverse resistance. The hydraulic transmissivity estimates map revealed higher values in the central portion of the area, highlighting the most significant transversal resistances associated with the highest hydraulic transmissivities. Therefore, this portion is the most promising for future well locations.

The discoveries of oil fields in the African Equatorial Margin combined with the drilling of wells such as Pecém and Pitu in the Ceará and Potiguar basins, respectively, reinforce the necessity for studies which aim to better understand the evolution of the sedimentary basins within the Brazilian Equatorial Margin (BEM), emerging as a new frontier for hydrocarbon exploration. The tectonic-structural complexity of the Equatorial Margin is discussed in several works, which classify this region as a transforming passive margin. However, there is a gap in the research of this basins when it comes to the concepts of Sequence Stratigraphy. The Ceará Basin is placed in the continental shelf of the Equatorial Margin and its origin is connected to the Gondwana’s breakup process during the Lower Cretaceous, resulting in the Equatorial Atlantic opening. The basin is limited to the southeast by the Fortaleza High, to the west by the Tutóia High, to the north by the southern part of the Romanche Fracture Zone, and to the south by the crystalline basement. Due to the distinct tectonic aspects and different structural framework, The Ceará Basin can be divided into four sub-basins, from west to east: Piauí-Camocim, Acaraú, Icaraí and Mundaú. The tectonic-sedimentary evolution of the Mundaú Sub-basin is composed by three super sequences: rift, post-rift and drift. In lithostratigraphic terms, the rift and post-rift stages correspond to the Mundaú and Paracuru formations, respectively, which were studied in this work from the well data, allowing the elaboration of 1D diagrams with lithofaces, cycles, sets of cycles and depositional sequences. The seismic stratigraphic analysis was carried out from 2D seismic lines, and consisted of characterizing seismic facies, reflectors terminations and bounding surfaces. The integration of these data and interpretations allowed the separation of the studied section in terms of tectonic systems tratcs and seismic stratigraphic units. Therefore, a model for the tectonic stratigraphic evolution of the basin was proposed.

The continental shelf of northeastern Brazil is characterized by a semi-arid climate, warm temperatures, clear waters, low sedimentary input, and mixed sedimentation, carbonatesiliciclastic. In this study, statistical analyzes, mean grain size, sorting, skewness, and kurtosis were applied to 123 superficial sedimentary samples from the outer shelf of Rio Grande do Norte to verify the controlling factors of the sediment distribution. In addition,
geochemical analysis using X-ray diffraction (XRD) methods in 18 samples, X-ray fluorescence (XFR) in 20 samples, scanning electron microscopy, and dispersive energy spectroscopy (SEM / EDS) in 10 samples. Another technique used was digital image processing applied to Landsat 8 / OLI satellite images in order to assess the spatial distribution of the submerged features on the continental shelf between Amazonas and Bahia. The main results demonstrated that the statistical parameters skewness and kurtosis were the ones that most evidenced the distinction between siliciclastic and carbonate sediments from the outer shelf, the chemical compositions differ between siliciclastic facies, composed by Si, Al, Fe, K, Zr, and Ti and the bioclastic facies, consisting of the elements Ca, Sr and Mg. As for digital mapping, reefs occur in waters from 10 to 35 m deep, paleochannels showed a maximum length of 25 km at depths of up to 80 m and underwater dunes have average lengths ranging from 300 to 8 km at depths of 10 to 100 m. Therefore, the integration of these data, showed that the bioclastic sediments come from in situ production and the siliciclastics are relict and derived from continental rocks. The occurrence of reefs, paleovalleys, and dunes indicates similar and favorable conditions for the establishment of these features during the Holocene along the Brazilian continental shelf

Predicting sub-seismic structures in carbonate reservoirs is a technological gap for reservoir models and new exploration targets. This study aims to understand the geological controls on the permeability-porosity distribution in fractured and karstified carbonates rocks of the Jandaíra Formation, Potiguar Basin, Brazil. The present study investigates the concentration of karst in an anticlinal hinge zone and below a subaerial unconformity. This study area lies in a karstic valley formed by collapse of galleries and cave walls. The methodology integrates satellite and drone imagery, aerial photography associated with the digital terrain model, 2D seismic data, exploratory well logs, field, and laboratory (mineralogy, geochemistry, petrology, petrophysics) data. A regional-scale fold with a NE-SW-oriented axis plunging to NE occurs in the area. It is parallel to the current drainage of the Apodi-Mossoró River and consistent with an NW-SE-oriented compression in a strike-slip stress field. Our findings indicate that fracture intensity is higher in fold limbs, forming a high-permeability roughly vertical high-permeability corridor. Far from the fold limb, the karst features are mainly at the surface. In addition, caves systems and conduits are concentrated below subaerial unconformities, which was formed by superposed epigenetic dissolution. The sedimentary sequence below the unconformity is composed of dolomitic peritidal deposits, whereas de sequence above the unconformity consists of tight-cemented calcite subtidal deposits. The karst features associated with the unconformity form a high-permeability zone of regional extent. Both sequences are recognized across the basin. The present study implies that superposed rock exposure, fracturing, and hydrological dynamics are key elements that influence epigenic karstification of carbonate reservoirs. They control the lateral reservoir zonation, whereas faults and fractures concentrate porosity within the vadose/phreatic hydrological zones. The present study presents a multidisciplinary and multiscale approach to analyze the karstification in carbonate rocks. It contributes to predicting the occurrence, distribution, and concentration of karst features in carbonate units and the consequent increase in permeability-porosity in carbonate reservoirs.

Parabolic dunes occur usually in coastal environments of tropical zones, and consist an important role in the ecological succession of coastal fauna and flora, composing habitat for certain species. A simple model for parabolic dunes internal strata and its correlation with geomorphologic features is proposed. Ground Penetrating Radar (GPR) and altimetric data were acquired in crossline and inline directions in two dune fields in northeast Brazil: Rio do Fogo/RN and São Bento do Norte/RN. PETREL environment was used for the 2D data interpretation, with geophysical attributes application. Five radar facies were interpreted and delimitation of four bounding surfaces was seen, in the hierarchy order: deflation, inundation, superposition, and reactivation. A conceptual model of parabolic dunes is proposed for depositional lobe, trailing arms, back ridges, trailing ridges, and deflation basin.

The São João do Sabugi Pluton, near the homonymous city in the Rio Grande do Norte state, is one of the most expressive occurrences of shoshonitic rocks within the Rio Piranhas – Seridó Domain of the Borborema Province. The petrography and chemistry (whole-rock and mineral chemistry) of the pluton was investigated in order to better characterize the involved magmatic differentiation processes and the crystallization conditions. The identified lithotypes were grouped into three petrographic facies: dioritic facies, with gabbro-dioritic rocks containing the mafic paragenesis clinopyroxene ± orthopyroxene ± amphibole ± biotite; monzodioritic facies, including diorite and monzodiorites, as well as quartz monzonites with amphibole ± biotite; and granodioritic facies, with the more felsic and evolved lithotypes containing biotite as the main mafic mineral, and higher contents of alkaline feldspar over plagioclase. The studied rocks are metaluminous and show high-K calc-alkaline to shoshonitic signatures. Textural evidences and geochemical modeling suggest that the pluton magmatic evolution was mainly governed by fractional crystallization processes coupled with assimilation of paragneisses and calc-silicate rocks of the Jucurutu Formation (AFC processes). The magmas that have built the São João do Sabugi Pluton crystallized at temperatures of 730 – 740 o C, under pressures of 5 – 6 kbar.

The study area is located in the Pirangi River Basin, Metropolitan Region of Natal, covering 370 km². The Barreiras Aquifer System (SAB) in the study area has high hydrogeological potential and the capture of its waters has been essential for the water supply of urban and rural populations and the industrial and agricultural development of the region. However, disordered urban growth and the adoption of inappropriate agricultural practices have threatened the quality of this underground spring. Based on the above, this study evaluates the hydrochemical behavior and water quality of SAB in the Pirangi River Basin region, as well as mapping the natural and anthropic vulnerability to aquifer contamination. The analyzes consider mapping of land use and occupation. For the hydrochemical study, a 30-well monitoring network was defined, followed by a collection campaign and physicochemical analysis of water samples. The interpretation of the results was made through isovalor maps and hydrochemical diagrams. Regarding water quality, groundwater was evaluated for human consumption, agricultural purposes and industrial use. The mapping of SAB vulnerability to contamination was performed by applying GOD, DRASTIC and IS methods based on the analysis and interpretation of 38 lithological profiles of wells distributed in the study area and cartographic data from previous works. Despite the hydrochemical variations observed in the different sectors, SAB groundwater in the study area is generally characterized as slightly acidic and of low salinity, predominantly encompassing magnesian sodium chloride (Na + - Mg2 + - Cl-) and chlorinated sodium facies. (Na + - Cl-). The climatic aspect is the main controlling factor of the chemistry of these waters, with the influence of anthropogenic factors of urban development and agricultural activities (nitrate contamination). As for quality, 70% of the samples evaluated can be destined for human consumption; for agricultural purposes there is no restriction on use; and for industrial application there were mainly restrictions on the paper, textile, beer, dairy and canning industries. The mapping of vulnerability to SAB contamination resulted in a predominantly low and intermediate vulnerability index for the urban zone through the GOD and DRASTIC methods and an intermediate index through the IS method. In the areas of agricultural development and in the area of lagoons and dunes with little human intervention, low and intermediate vulnerability indices were determined using the DRASTIC and IS methods, while the GOD method has a predominance of high vulnerability.

Physical modeling is a tool that has been widely applied in several fields of geology, in particular, structural geology focusing on the tectonics of sedimentary basins and mountain ranges formation, and their associated processes. In this research, analogical physical modeling was used to investigate the influence of rheology on the nucleation and evolution of secondary structures associated with transcurrent tectonics. The experimental models performed in a sandbox apparatus were monitored by conventional photographs, Laser Scanner and Particle Image Velocimetry (PIV). This latest enabled the analysis of the strain distribution within the damage zone, the structures nucleation, their relative chronological relationships and their influence on the topographic evolution of the deformed area. The experiments simulated the development of secondary structures nucleated during a progressive deformation in a dextral shear zone. The models were executed with granular analog materials of different rheological behaviors, such as quartz sand, dry clay, plaster powder and a mixture of sand and plaster powder. The physical properties of these materials were characterized by Ring Shear Tester (RST). Along with the deformational evolution of the experiments, secondary fractures (R, R’, P, Y), pull-apart basin, positive and negative flowers (transpressive and transtrative sites, respectively) and block rotation were analyzed qualitatively. Models constituted of different pre-tectonic sequences without rheological contrasts (a single type of granular material) displayed a geometrical and evolutional diversified structural framework conditioning to the used material. Experiments with rheological stratification (pre-tectonic sequences with different granular materials) displayed a structural architecture distinct from rheological homogeneous models. Our results confirm that rheology has a significant role in the arrangement of secondary faults and their relative chronology during the transcurrent tectonics. These experimental analyses corroborate with natural examples available in the literature

The present work comprises the results of the description of vibra cores collected in recent sediments deposited in the Parnaíba river delta, located on the border between the states of Piauí and Maranhão, in the Barreirinhas basin. Because of the low number of inhabitants and the low socioeconomic development of the Brazilian Northeast region, the Parnaíba River delta is a rare example of this environment deposit system that still presents a large part of its natural features with few human interventions. On the delta, 9 cores were collected by the method of vibration which result in 14,86 meters. A granulometric, compositional, mofoscopic and mineralogical analysis was carried out in a total of 295 samples from these 9 cores aiming to carry out a study of sedimentary provenance in the delta and identify changes in the depositional environment that may be related to the lateral migration of the main channel of the Parnaíba river and to the isolation of the western portion of the delta during the Holocene. Ascending granodecresence was observed in the four cores. At the tops, we have very fine sands or mud with high contents of organic matter and calcium carbonate (CaCO3). At the intermediary section occurs a variation between very fine sand and medium sand with present a decrease in the contents of organic matter and CaCO₃. At the base occurs fine sand with low levels of organic matter and CaCO₃. The transition between mudy and sandy environments occurs abruptly, however concordantly, between depths of 42 and 72 cm. The mineralogy at the basis of the cores in the western portion of the delta, close to the city of Tutóia shows great similarities with the mineralogy of the cores located in the main channel of the Parnaíba river. However, tops have significant variations indicating that in the past, the Parnaíba river deposited sediments directly in the western portion of the delta but at some point this reality has changed Possibly, in this period the main channel ran through the western portion and the great tidal channels of the delta are in fact ancient main channels that were abandoned during the evolution of the lateral migration of the river

The Barreirinhas Basin is located in the central portion of the Brazilian Equatorial Margin (MEB). Its origin is linked to the rifting and fragmentation process of West Gondwana in the Early Tertiary. It happened when the continental lithosphere in the north of the Barreinhas Basin was uplifted and fractured by transforming movements Romanche Fracture Zone (RFZ). This basin was controlled by a mixed tectonic regime: distensional efforts, resulted from the separation of the Supercontinent, associated with shearing efforts. One of the objectives is to investigate how the RFZ has been influencing the evolutionary history and the main structures of the Barreirinhas Basin. In addition, the study was important to favoring the contribution of knowledge about the region through the construction of geophysical and geological models, which structurally and stratigraphically portray the internal architecture offshore and onshore portions of the basin. For this purpose, eight 2D seismic sections were interpreted together with information from five well geophysical profiles. In order to assist in the interpretation process, seismic attributes were used to highlight both seismic stratigraphic horizons and structural features. The results show the predominance of lytic faults of normal tailings in the rift sequence and the presence of transtensional kinematics, represented by negative flower structures, due to the dextral movement during the separation of South America and Africa. In the more distal portions of the emerged basin, it is observed that reactivations of the RFZ influenced from Aptiano structures to the Holocene, and therefore have a strong impact on the evolutionary history of the Brazilian Equatorial Margin, in particular, the Barreirinhas basin

The Potiguar Basin comprises one of the basins of the Cretaceous Continental Rifts system, an important event that occurred in the implantation of the Brazilian equatorial margin in northeastern Brazil, evincing a noteworthy region of hydrocarbon accumulations. In order to better understand the tectonic-stratigraphic evolution of the Potiguar Basin, this work aims to contribute to the study of the sedimentary record of the basin's rift and post-rift sections through the stratigraphic analysis of wells and seismic data. The study area is settled by this post-stack seismic volume known as Pescada Field, comprising the wells and seismic lines scrutinized. The first phase of interpretation, the 1D analysis of six exploratory wells, made it possible to characterize the main lithofacies and depositional systems of Pendência, Pescada and Alagamar formations, and also to recognize the main units of sequence stratigraphy, such as cycles, key surfaces and systems tracts, with the definition of three depositional sequences on a regional scale. The 2D interpretation displays a structural arrangement consisting of grabens/semi-grabens, internal highs, and an important fault system of NW-SE to E-W trends that affect the layers and gave rise to additional structures of rift context. Furthermore, the stratigraphic framework enabled the identification of the main boundary surfaces, seismic facies and seven tectonic system tracts that comprise the rift and post-rift sections and reflect the progress of active tectonism, from the initial rifting and two stages of high/low tectonic activity in the basin installation. The integration of all results reveals the effective application of sequence stratigraphy in the study area.

Located in the São José do Campestre Massif, the Senador Elói de Souza Complex is a geological unit composed of 3.03 Ga granitic to tonalitic orthogneisses, mafic and ultramafic rocks characterized by metagabbros, metaclinopyroxenites and anorthosites with garnet and oligoclase, with the ultramafic bodies and carbonatites dated at 600 ± 03 Ma. These bodies have contact features evidenced through magmatic breccias with carbonate matrix and involving pyroxenite fragments. In addition, field data and 2D gravimetric modeling allowed interpreting carbonatites and pyroxenites as ellipsoidal bodies, the first one less expressive along the borders of the intrusion complex. The analysis of gravimetric data suggests they ate shallow bodies and appear to truncate the low angle structures of the basement gneiss rocks. Clinopyroxenites have a well-preserved igneous texture, a low fractional pattern of rare earth elements [(La_N/Yb_N) = 8.9-49.8] and negative Eu anomaly of (Eu/Eu* = 0.39-0.88). Carbonatites are calcite-rich, with diopside, phlogopite and olivine as main mafic phases, low concentration of rare earth elements, with parallel and slightly inclined patterns [(La_N/Yb_N) = 1.5-8.6], in addition to enrichment of rare earth elements lightweight compared to heavy rare earth elements. The distinct geochemical behavior between these lithologies in Harker-type diagrams, in addition to a magmatic gap, suggests partial mixture of magmas. Occurrences of symplectite between clinopyroxene and plagioclase and grossular partially consumed generating scapolite indicate retrogression processes in clinopyroxenite. Recrystallization of calcite, serpentinization of olivine and deformation of phlogopite in carbonatite indicate the action of metamorphic events and fluid-rich (CO₂, H₂O) metasomatism. The geological and geophysical data reported here may contribute to understand the Ediacaran mantelic events in the Archean domain of the São José do Campestre Massif

Volcanic rocks, especially basalts, commonly have vesicles generated by the escape (expansion) of gases during the cooling process. These vesicles can be filled (turning into amygdales) by different mineral assemblages through the circulation of hydrothermal or meteoric fluids. The identification and characterization of these secondary assemblages, as well as their processes and formation conditions can provide important insights on the
subsolidus history of volcanic rocks, such as the evolution and compositional and physical-chemical factors of the fluids involved, chemical balance and mineralizing processes. The northern portion of the Borborema Province was affected during the Mesozoic by an important continental tholeiitic volcanism related to the Gondwana breakup and the opening of the Equatorial Atlantic Ocean. This magmatism manifests itself mainly as the Rio Ceará-Mirim dike swarm (CMD) and the Serra do Cuó basaltic flow (SCB), whose basalts and diabases are often vesicular and amygdaloidal. The detailed characterization of the secondary/hydrothermal mineralogy in these rocks is still an unraveled research topic, therefore this work aims to fill this gap with a systematic mineralogical study of amygdales from selected samples of CMD and SCB volcanics, based on petrographic, X-ray diffraction (XRD), thermogravimetric (TGA/DTA) and mineral chemical (EDS) data. The results show that the CMD amygdales are predominantly monomineralic, filled with laumontite and, locally, quartz or calcite. Laumontite was probably formed at temperatures of ~125oC after a higher temperature (up to ~300oC) hydrothermal event that changed the primary mineralogy to mafic phyllosilicates. Infillings in the SCB amygdales are polymineralic, defined by the initial low-temperature (~150oC) formation of nontronite/saponite on the cavity walls, followed by the precipitation of natrolite and/or phillipsite, reflecting changes in compositional and temperatures (up to ~250oC) of the meteoric fluids from which these phases have precipitated. A late low-temperature stage is marked by the alteration of zeolites to clay minerals. It is inferred that the needed chemical components for the formation of these mineral assemblages result from the destabilization and alteration of interstitial volcanic glass, primary mafic minerals and plagioclase caused by the percolation of meteoric fluids within the rocks during their cooling. The observed mineralogical variability in the CMD and SCB amygdales points to contrasting compositions of these fluids which ultimately reflect the compositional (chemical and mineralogical) differences between the two volcanisms, as well as external contributions.

This dissertation presents the results of the application of the Seismic Reflection Method together with data from some boreholes in a aseismic ridge in the South Atlantic Ocean called Rio Grande Rise, which is about 1500 km from Rio de Janeiro, in international waters. There are approximately 100 Ma volcanic sills in the oceanic crust, caused by the Tristan - Gough hot spot that would have caused this Elevation. After that, around 97-90 Ma the Meso-Atlantic Ridge would have broken the oceanic crust and the Rise would have become part of the South American plate. Then a phase of pelagic sedimentation begins in shallow water environment on the raised crust by volcanic spill. In the Upper Cretaceous, intense rifting affected the Rise resulting from extensional plate settling forces and the opening movement of the South Atlantic Ocean. In the Middle to Upper Eocene, sedimentary fill of significant thickness continued be deposited. Also in the Eocene expressive magmatism due to pressure relief, caused by the extensional tectonics, occurred in the Rise and forming several guyots and exposing part of the Rise above sea level. When the magmatism ceased between the Eocene and Oligocene, the Rise was cooled, subsidized, eroded, and submerged.

The objective of this dissertation was to reprocess vintage seismic lines in order to obtain better images and new information of tectono-depositional sequences in the Rio Grande Rise. The seismic data have been correlated with a DSDP borehole to obtain seismic stratigraphic interpretations and a sequence of evolutionary stages, based on a priori knowledge, and thus provide more complete explanations of the tectonic, volcanic and sedimentary evolution of the Rise. It also aimed to find correlation points between the Rise and the adjacent continental margin. Four seismic lines were reprocessed using Promax® software. Then, the stratigraphic units described in the borehole close to the lines were correlated. And so it was generated seismic interpretations and evolutionary model of the Rio Grande Rise. Interpretations of three seismic lines located in the vicinity of the Rise were also made.

Our results show that the uplift of the central portion of the Rio Grande Rise was responsible for the appearance of inclined reflectors within the basement, on both sides of the Rise. The interpretation of the sedimentary package shows that the causative extensional pulse of the Cruzeiro do Sul Rift would have been active from the Maastrichtian to the Middle / Upper Eocene. Another rift on the eastern slope of the central portion of the Rise is interpreted, recent reactivation being noted. Faults ranging from acoustic basement to the most superficial units of the sedimentary package plus aborted rift are evidence that this extensional tectonic remains active from the Late Cretaceous to the Recent. Still regarding tectonics, the effects of strike-slip movements along the Porto Alegre Fracture Zone were also observed in the sedimentary package. This fracture zone was imaged in seismic between two guyots. This sinistral strike-slip movement would have displaced the axis of the Cruzeiro do Sul Rift about 90 km eastwards in the Upper Cretaceous. We have also postulated, from volcanic breaches and ash identified in some boreholes, a thermal anomaly of great proportion due to the magmatism that raised the central portion of the Rise. We also observed improved imaging of mounds within the sedimentary package, which are possibly associated with intrusive Eocene volcanism or hydrothermal activity at the base of the sedimentary package and / or gas chimneys due to warming associated with the magmatism. These latter hypotheses are corroborated by depressions of about 500 m in diameter on the ocean floor and polygonal faults that may be related to the presence of fluids and pockmarks. Finally, similarities between seismic facies and extensional tectonic events in the Upper Cretaceous and Eocene volcanism point to a correlated evolution between the Rio Grande Rise and the adjacent continental margin.

This dissertation represents new knowledge about the Rio Grande Rise and its surroundings, which may be useful for future scientific purposes and exploration of mineral resources.

The present work investigates the formation and compartmentalization processes of the fault zones and hydrothermal silicification in the Rio do Peixe Basin, Brazil, observing these processes' impact on the host siliciclastic rocks. For this, we mapped six outcrops with the aid of unmanned aerial vehicle (UAV), structural mapping, petrography, scanning electron microscopy (SEM), spectroscopy dispersive energy (SDE), X-ray diffractometry (XRD), and fluid inclusion analyses. We observed that the fault zones have a core with a high degree of cataclase, reducing the size of the grains, primary and secondary porosity. Next to the core, a damage zone is characterized by single deformation bands or clusters, where the content of clay minerals vary significantly. The borders fault zones have silicification bands up to 250 m thick. Throughout these bands, silicification varies in intensity and can show a static or dynamic pattern. Deformation bands, hydraulic gaps close to the main fault plane, and silicified basement rocks with quartz veins are found in these places. Within the primary or secondary pores, there are occurrences of newly formed minerals such as kaolinite, chalcedony, apatite, and barite, representing the interaction between the heated hydrothermal fluid and the host rock. Silicification is associated with ascents of hydrothermal fluids along the deepest faults, varying in temperature conditions between 89 ° C and 240 ° C and 30-80 Mpa pressure. From the results obtained, we conclude that the composition of the framework and the clays' mineralogy do not vary along the fault zone, despite the content of clay minerals being systematically lower in the most deformed rocks. They have a weathering origin, unrelated to the fault activity. On the other hand, the silicification of the border faults is linked to the fault dynamics, because they suffer reactivation from the rise of hydrothermal fluids formed at high pressures and prices. Therefore, the cataclase and the hydrothermal silicification processes have important implications for aquifers and hydrocarbon reservoirs

The northeastern portion of the Borborema Province (PB), in northeastern Brazil, is marked by a voluminous Ediacaran magmatism that intrudes the paleoproterozoic gneiss-migmatitic basement (the Caicó Complex) and neoproterozoic metasupracrustal rocks (the Seridó Group). In this context, the Umarizal pluton, the focus of this work, is classified among the Ediacaran types as the Charnockite alkaline suite (AlcCh). The main objective of this research is the reevaluation of previous interpretations through new field data concerning emplacement mechanism, dating plutonic rocks and of neosome of thermally affected hosting units and thermal modeling of magma cooling. The obtained results showed that the magmatic suite is composed of three distinct petrographic facies, where the Umarizal and Ação facies are restricted to the Umarizal pluton and the Lagoa facies is found as minor bodies intruding in the Tourão pluton. Usually the AlcCh Suite is composed of quartz-syenite and quartz-monzonite and their charnockitic equivalents. Structurally, the main pluton is emplaced between the NE-SW Portalegre and NE-SW Frutuoso Gomes shear zones. Field criteria suggest that these lineaments had progressive movements, begining with synistral extensional that favoured the emplacement of the Umarizal magma and finished with dextral contractional movement. Synchronously with the emplacement, a thermal aureole of up to 1-2 km thick was formed in Formação Jucurutu country rocks, with Buchan-type metamorphic associations, registered in andaluzite - sillimanite in paragnaisses, scapolite in calciosilicatic gneisses and flogopite in marbles. The U-Pb age of 583 ± 1.8 Ma, obtained in zircons from a neosome, is similar, within error, to the zircon U-Pb ages of the Tourão (589.3 ± 4.4 Ma) and Umarizal (565 ± 22 Ma) plutons. Modal and lithogeochemical compositions configure two suites, one of probable mantle derivation (gabbro-norites, anorthosites) and another crustal-derived (granites and charnoquites), thus characterizing an anorthosite - mangerite - rapakivi-granite – granite magmatic association. The mineralogical variation from the least differentiated facies to the most evolved facies suggests the dominance anhydrous conditions (fayalite, hyperstene, diopside-hedenbergite) at the beginning of crystallization to water subsaturated at the end of evolution and, thus, favouring the formation of hornblende and biotite. The initial crystallization conditions of the charnockite suite indicate control by the fayalite-magnetite-quartz buffer, with pressures of ~ 9 kbar and temperatures in the order of 900-1100 ° C. On the other hand, geothermobarometric data using Al-in hornblende allowed to calculate approximate conditions of 4.5 ± 0.6 kbar and 755 ± 32 ° C for the final crystallization stage. The integration of mineralogical and petrophysical data of the plutonic units and the thermal aureole allowed the thermal modeling of the cooling magma, being coherent with conditions of high geothermal gradient (40 °C / km), peak of thermal metamorphism in 15,000 - 80,000 years after emplacement, and thermal conditions extending to 1 - 2 km away from the contact. Considering the existence of countless other batholithic bodies of the same age in this part of the PB, it is proposed that the Ediacaran was a period of extensive crustal heating under conditions of high geothermal gradient, possibly due to the heating driven by underplating of mantelic (gabbro-norite) magmas.

The mapping of subsurface features can contribute to the understanding the chronostratigraphic boundaries associated with distinct depositional phases, as well as to record the hydrodynamic conditions in the system. High resolution seismic, in this context, is widely used to delimitation of surfaces and structures allowing the understanding of the sedimentary evolution - its seismostratigraphy. The purpose of this study is to establish a relationship between the events and the chronostratigraphic boundaries associated with the sea level changes in the shelf during the Quaternary, in order to define the sedimentary evolution of the inner Continental Shelf adjacent to the city of Natal/RN. Thus, 31 lines (transversal and longitudinal) were distributed in 62 km along the inner shelf, using a boomer system that operates with energy of 300 J and frequency 1-2 kHz. The acquired data were later processed in the software ReflexWin 8.0, in which a flow processing was established that enhanced the seismic sections and the visualization of the reflectors. Through the analysis of the profiles, three main horizons, D01, D02 and D03, from bottom to top, respectively, representing the boundaries between the Seismic Units (U01, U02 and U03) were identified. The D01 horizon is represented by a large, discontinuous, high-amplitude sinuous surface that reaches 40 m depth and is located below Unit U01. The D02 horizon is an irregular, sometimes tabular, sometimes like depression surface that reaches 20 m deep. It is the boundary between Units U01 and U02. The horizon D03 is a parallel/subparallel surface that reaches up to 4 m deep and divides Units U02 and U03. Unit U01 has low continuity and frequency, varied amplitudes, and subparallel to chaotic configurations. The U02 Unit has high continuity, low frequency, moderate amplitude and configurations that range from parallels to sigmoidal clinoforms. The U01 and U02 are interpreted deposits developed in higher energy conditions. The U03 Unit features high continuity, low frequency, high amplitude and parallel configurations. This unit is interpreted as a depositional phase of lower energy. The D02 horizon represents an erosive surface that possibly represents the Pleistocene-Holocene chronostratigraphic boundary.

This study aims to apply a special processing in the investigation of gas chimneys in the Parnaíba Basin and, to use this knowledge, as an exploratory tool in hydrocarbon research. The new processing methodology aims to facilitate the visualization process in seismic of the gas chimneys by frequency spectrum enhancement of the seismic signal in the Hilbert domain. Allowing for an amplification of the information concerning the petroleum system, this research methodology diminishes the high exploratory risks inherent to the frontier basins with high territorial extension such as the Parnaíba Basin. Other basins that were also visited in this dissertation using this technology were the Paraná and Tacutu basins. Often the seismic response of gas chimneys is treated as noise or even their presence is not even perceived in conventional PSTM seismic processing. This work shows a processing methodology that seeks to highlight the gas chimneys and make their interpretation in the seismic profiles unequivocal. Its sismofacies consists of chaotic and low-frequency disturbances that interrupts the lateral continuity of good reflectors and its origin is related to migration of fluids or free gas in its path between the source rock and the reservoir rock. In addition, this research, by observing the rooting of the gas chimneys in the basin grabens, strongly indicates a new petroleum system associated with the deposits present in the pre-silurian grabens. To prove that these seismic features enhanced by the new processing are actually gas chimneys, a validation work was carried out to identify topographic, seismic and geochemical features that occur in other sedimentary basins associated with the presence of gas chimneys. To facilitate the management of future exploratory process by directing the new seismic programs to be acquired, a table was elaborated with the different types of traps associated to gas chimneys found in this basin and their respective probabilities of success considering the results obtained in this basin and in other parts of the world. Those most likely to succeed should be those chosen for further seismic detailing. Considering the quantity of gas chimneys encountered with this special processing, the significant area of the structures found and the other direct hydrocarbons indicators revealed in the work, it can be affirmed that one faces  a high potential basin for commercial discoveries of hydrocarbons and with relatively low risk.

The origin and evolution of the Pantanal Basin has been investigated through velocity-depth profiles developed from the joint inversion of receiver functions and surface-wave dispersion velocities at 32 broadband stations. The Pantanal Basin is a shallow and wide depression in South-Central Brazil that developed within the Andean foreland in response to loads and flexural bending of the South American plate. Our results reveal the existence of up to four different crustal types that correlate with surface geology: (i) crust of 35 km with V_S < 4.0 km/s, under the basin and along the SW projection of the Transbrasiliano Lineament (TBL); (ii) crust of 45 km with V_S > 4.0 km/s below 40 km depth, flanking the basin to the East and West; (iii) crust of 50-55 km with V_S > 4.0 km/s below 40 km depth, flanking the basin to the North and South and along the TBL; and (iv) crust of 42.5-45.0 km with V_S < 4.0 km/s in the neighboring Paraná Basin. Existing geodynamic models propose that the Pantanal Basin formed either in the backbulge of the flexural system or at the top of the flexural forebulge, due to extensional bending stresses that reactivated pre-existing faults in the shallow upper crust. We argue that the Pantanal Basin formed in a structurally weaker portion of the foreland crust that was affected by delamination and enhanced bending of the South American plate. Our findings do not allow for discrimination among the competing models, but suggest the TBL was critical in marking the location, origin and evolution of this basin. 

Stock Serra do Capuxu (SSC) is located in the northern portion of Borborema Province, in the southwest of the Rio Piranhas-Seridó Domain. The SSC intrudes gneissic rocks of Caicó Complex, which holds xenoliths, and truncates previous ductile features. MME-type enclaves occur locally with mixing and mingling features, and multiple and complex schlierens. The SSC is characterized by leucocratic rocks (∑Mafics=7,5-13%) of monzogranitic composition, equigranular texture, occurring locally K-feldspar phenocrystals (microcline). K-feldspar+ plagioclase+quartz constitute more than 85% modal; biotite is the main mafic (6-10%); titanite, opaque, allanite and zircon are accessories; and chlorite, muscovite and carbonate occur as products of tardi-magmatic transformations. These rocks are highly evolved (SiO₂=71.80-73.14), with high alkali contents (Na₂O+K₂O=8.25-8.77) and low Calcium contents (CaO=1.23-1.69). The Rare Earth Elements spectra (REE) shows enrichment of lightly versus heavy REE’s, with pronounced negative Europium anomaly (Ce_N/Sm_N=4.8-5.7; Gd_N/Yb_N=1.6-2.2 and Eu/Eu*=0.34-0.44). The alumina saturation index reveals a metaluminous to peraluminous transitional character (A/CNK=0.98-1.03). Discriminating diagrams of magmatic series reveal mostly chemical affinity with subalkaliine (high-K calc-alkaline) rocks and tectonic environment classification diagrams associate SSC with post-collisional environment. These data are corroborated by the U-Pb zircon age of 579 Ma found for stock, suggesting late emplacement (post-tectonic) of SSC. An eminently crustal source for the SSC is postulated, possibly fusion of basement gneisses (low fusion, due to its high and little varied SiO₂ contents) generating a magma already of high-K calc-alkaline nature. Rocks with similar chemestry signatures have been called “Fractionated I-Type Granites”.

Early Jurassic basic magmatism of the Parnaíba Syneclise (Northeast Brazil) is represented by the Mosquito Suite, which is part of the important Central Atlantic Magmatic Province (CAMP). The unit is relatively well studied from the petrological and geochemical points of view and has a number of geochronological ages. This magmatism is mapped in a regional scale and described at the surface as dominated by flows. In subsurface, it is characterized by an important sill complex, evidenced by magnetometric, seismic reflection, and well data. Besides subordinate exposures in southern portion of the basin, the main occurrence of (sub)volcanic rocks of this suite is located in central-western portion of the basin, focus of this study. Magmatic bodies of the unit are associated with an E-W to ENE-trending expressive lineament pattern, also observed in plateaus supported by these basic rocks and eolian sandstones of the Sambaíba Formation, for which a Middle Triassic age is assumed. In this work, the structural controls and stratigraphic relations of the Mosquito Magmatic Suite were approached. The methodology involved interpretation of orbital remote sensing images (optical and radar) and field data, including the characterization of faults and contact relations of magmatic bodies with the sedimentary units. Petrographic studies were performed and subsurface information was obtained from well profiles. As a result, the area previously mapped as Mosquito Suite was restricted, mostly corresponding to the Sambaíba Formation sandstones intruded by sills (besides feeder intrusions). A younger unit of sandstones was named as intervolcanic, displaying clasts of the basic rocks. It occurs intercalated with likely flows and shallow sills, at the top of the plateaus or at lower elevations, when affected by faults. Macro and mesoscale structural analysis characterized an Early Jurassic deformational event, with NNW-trending extension direction, which controlled the emplacement of magmatic bodies of the Mosquito Suite. Previous fractures were also used for the intrusion emplacement. Different types of interactions between sills, feeder bodies, and their sedimentary country rocks are described, ranging from non-brittle style (viscous regime structures) to brittle style. The tabular sub-horizontal geometry of the bodies (including cross-sections with shapes of steps and fingers), xenoliths, contact-metamorphic aureoles, besides the country rock fluidization, as shown by the thermal carapaces, peperites, and injection clastic dikes attest the dominance of sills at the present surface. The Early Jurassic deformation, responsible for the structural control of these magmatic bodies, represents distal effects related to the opening of the Central Atlantic. The important magmatic component in this syneclise certainly contributed to its history of subsidence and uplifts. This magmatic event has important implications for the formation of atypical petroleum systems in this basin, which is still considered as an exploratory frontier.

The onshore Potiguar Rift is the result of the first rifting phase (Berriasiano - Barremiano) that gave rise to the Potiguar Basin. Its structural framework is complex, consisting of semi-grabens, internal highs and important interacting fault systems. A relatively younger rifting phase is attributed to the Aptian. Two major fault systems have controlled the origin and evolution of the basin: the Baixa Grande and Carnaubais fault systems, which delimit the Umbuzeiro semi-graben, the main depocenter of the rift. Despite the existence of a well-established structural framework, there is still no consensus on how these structures evolved. This work aimed to analyze the eastern margin of the onshore Potiguar basin, where the main faults and depocenters systems of the rift stage are located. Analysis of seismic data (2D and 3D) and available geophysical profiles of some wells showed that both fault systems evolved through nucleation, relay ramp interaction, and connection of diachronic and echelon fault segments of a smaller order. Each diachronic segment conditioned the accumulation of sedimentary sequences and, when they interacted with each other, an angular discontinuity was formed. The mechanical connection of the diachronic normal fault segments occurred by second-order fault nucleation (connection failure) in response to stress fields located in a contractional bridge between fault segments. The connection fault developed over the basement weakness zones (mylonitic fabrics) with a relatively smoother dip in relation to the main faults, resulting after a mechanical connection, in faults with ramp-flat-ramp geometry. This geometry induced the formation of anticlinals found in the vicinity of fault systems. The physical models corroborated the interpretations obtained with the seismic data and showed the importance of relay-ramp formation. A new model for the evolution of the eastern margin of the onshore Potiguar Rift and possible implications for the opening kinematics of the basin as well as for the exploration of hydrocarbons is proposed.

Carbonate rocks are recognized for their great heterogeneity and for the presence of structures associated with dissolution. This is very important in fractured regions, since fractures can induce dissolution processes. Among the consequences generated are secondary porosity and increased permeability, which is essential in regions with oil reservoirs. In addition, the increase in dissolution is responsible for the formation of collapse structures, which can occur both at the surface and in the subsurface. The collapses are responsible for several problems in urban areas built on this type of terrain, such as the collapse of buildings and roads, which can cause serious social and environmental problems. The work focused on the study of sinkholes, which are the most expressive collapse structures in carbonate rocks, and their relation with preexisting fractures. The occurrence of sinkholes in outcrops can help to answer questions intrinsic to the problems mentioned, such as if there is any interference in the structural and petrophysical properties of the affected rocks, or even to improve the prediction about the effects that the collapses generate in the topography. The studied area has two sets of preexisting fractures, one N-S / E- W and another NE-SW / NW-SE, which concentrate the main dissolution in the region. The presence of these fractures allowed the formation of the collapse sinkhole. The data showed that in areas where collapses occur, there is the formation of what are being called subsidence halos. This zone is suffering subsidence due to the main collapse, and the original relief is affected, plunging towards the sinkholes. Topographic relief variations greater than 10 meters in relation to the non-affected areas were measured. It was also observed that the affected area around the sinkholes has on average twice the radius of the sinkholes. This process generates a change in the pattern of fractures of the region, with the formation of a new set, called collapse fracture. These fractures are circular in shape and occur around the sinkholes. An increase in the aperture and density of these fractures when approaching the sinhkoles was also observed through scanlines. This represents an indicator of permo-porous quality improvement in these areas. In addition, it shows that there is an increase in structural instability, rising the risk of accidents in areas built on soluble rocks, since the affected area may be much larger than previously predicted.

We use a 5-h long experiment with 182 vertical 2 Hz sensors deployed on the surface to characterize noise before and during a hydraulic fracking monitoring in the Potiguar Basin, NE Brazil. We observe that the seismic noise is mainly from electromagnetic inductions and from machinery vibration near the wellhead, and within 2 km from the array center from pupjacks, pipelines, roads, and industrial facilities. We also report a resonance composed of body wave coming from the treated area which is only present when the injection takes place. We interpret this resonance resulting from fluid filled fractures in the subsurface maintaining waves that reverberate in the fractures. Different strategies were employed to cross-correlate and stack the data to Ambient Noise Seismic Interferometry: classical geometrical normalized cross-correlation (CCGN), phase cross-correlation (PCC), linear stacking and phase weighted stacking (PWS). PCC and PWS are based on the instantaneous phase coherence of analytic signals. Because of the unsuitable distribution of the noise source and geometry of acquisition, spurious arrivals arise in the correlograms. We proposed a simple methodology to attenuate these unwanted effects which consists of applying Linear Moveout (LMO) correction, stack the data in the shot domains and f-k filtering. The dispersion curves after this processing are improved and the results from the phase velocity analysis are consistent with those data from the literature.

The understanding of earthquake occurrence in intraplate areas has been one of the most difficult tasks in Seismology. Attenuation of seismic waves in these areas is lower compared to border plate regions. As a consequence, even moderate magnitude earthquakes can represent great hazard. In this case, assessing the stress field in intraplate regions is important to better understanding the earthquake generating mechanisms. We analyzed 241 earthquakes of the 2017 seismic sequence in NW Potiguar Basin and estimated the stress regime. Seismically defined faults were determined for 4 high-precision relocated NW-SE- and NE-SW-trending clusters. Faulting intersection acting in one of this clusters was representative for suggest Intersection model for intraplate earthquakes as possible explanation about why size moderate earthquake occur in the study region. Another cluster presented an en echelon fault with a clear spatiotemporal evolution and occurrence of almost entire activity in very short period, which suggest energy build-up and rapidly release between this fault segment.  We were be able to calculate composite focal mechanism for three clusters, with predominant strike-slip faulting with sinistral movement. The inversion of focal mechanisms reinforce evidence for a superposition of local and regional stresses, with major compressional axis subparallel to continental equatorial margin.

Currently, the greatest challenge to overcome in order to apply FWI is avoiding cycle-skipping. Accomplishing this goal requires an initial velocity model that has a significant amount of longwavelength information from the subsurface velocity distribution. In order to produce a suitable initial model, this thesis proposes an inversion approach composed of three stages. The output of each stage is the input of the next one. In the first stage, Dix-Stage, we build a model derived from a coarse Dix velocity analysis. In the second stage, K-Stage, we derive velocity models that honor the first-arrival traveltimes using a transmission inversion approach. In the third stage, FWI-Stage, a concluding waveform inversion process is carried out. The focus here is on the second stage, where we compare first-arrival traveltime tomography with the inversion of a misfit functional based on the windowed early arrivals of the envelope in producing starting models for the FWI-Stage, and on third stage. We use the Marmousi and Overthrust models to show that, in the K-Stage, the early-arrival envelope functional produces solutions with at least the same quality as those derived from first-arrival traveltime tomography. As a result, in the FWI-Stage, final velocity models with similar quality are obtained not mattering whether this stage was initialized with early-arrival envelope or with first-arrival traveltime tomography models. However, unlike the first-arrival traveltime tomography, the early-arrival envelope inversion does not require time picking, which could save an expressive amount of time. In addition, the early-arrival envelope functional is robust to noise. We conclude then that the early-arrival envelope functional has good potential to substitute first-arrival traveltime tomography in the K-Stage. However, neither earlyarrival envelope or traveltime functionals are free from problems and, as a result, the interpreter ultimately must judge the resulting velocity models to decide whether they are valid to initialize an FWI process. For the FWI Stage, we propose a sequence of different misfit functions in time domain. The employed misfit functions are sensitive to different wavelengths but use the same modeling algorithm and the same model grid. In the first and third inversion steps the transmitted (early arrivals) and reflected (late arrivals) components of the wavefield envelopes are respectively fitted. The second step promotes a smooth transition between the first and third steps, by using the envelope of the complete waveform. The phases of the reflected waves are mostly fitted in the fourth step, which is based on the waveform misfit function preserving only the late arrivals. The third and fourth steps are of crucial importance to fit the reflected events. We test this approach with the Marmousi model using datasets with different frequencies, obtaining better estimates of the velocity field than those obtained with the classic FWI. The solutions obtained with both classic FWI and sequential inversion approach degrade with a progressively higher peak frequency dataset, but the classic FWI solution degrades more rapidly.

This research investigates how fractures associated with the stress field (SH_max) influence the increase of porosity and secondary permeability, as well as the development of karst features of the carbonate rocks of Rosário Outcrop (Jandaíra Formation - Potiguar Basin). The study presents the interpretation of Unmanned Aerial Vehicle (UAV) images, numerical modeling data and field research. Through the UAV image was performed the structural interpretation and preparation of lineament maps, surface and topographic dissolution, and topographic profiles. The structural analysis performed in the field had the characterization of centimeter structures, such as veins, tectonic stylolites and distensional structures, as well as metric structures as normal faults. Numerical modeling investigates how fractures subjected to a maximum compression stress NW (current stress field in the Potiguar Basin) influences the dilatancy process and plastic flow and, consequently, the karstic development. Field results indicate that the main structures, generated by a transcurrent stress field with maximum horizontal compression NS and maximum horizontal distension ES, are compatible with NS veins, distensional fractures (I-mode) and E-W to ENE-WSW tectonic stylolites, perpendicular to stratification, compatible with the same stress field. The linkage of these structures forms continuous fractures up to 100 m in length and 15 m deep, which allows the fluid to flow vertically along the fracture planes, which can reach the depositional planes, also favoring horizontal dissolution. These plane intersection zones generate zones of high connectivity that leads to increased porosity and permeability, generating structurally controlled conduits, being responsible for the development of caves, collapse structures and large fractures. The results of the numerical models indicate that the accumulated stress along the pre-existing fractures generates zones that favor the increase of porosity and permeability, favoring the karstic development. NW fractures, orthogonal to the stress field (SH_max), and fractures at the intersection of NE-SW and NS fractures were the sites with the largest increase in dilatancy and the presence of plasticization, that is, the preferred sites for karstic development. The results of numerical modeling when compared to dissolution maps show realistic results for the development of karst features. The behavior of pre-existing fractures can greatly contribute to the understanding of the development of secondary porosity and permeability in carbonate rocks, as well as in the development of karst features.

Benthic foraminifera are widely used as bioindicators, especially in environments with high levels of pollution and anthropogenic interaction. We collected 59 sediment samples through Van Veen grab sampler, as well as physical-chemical data from the water column using the CTD (conductivity, temperature and depth) equipment. The objective is the sedimentary and environmental characterization of the Potengi River estuary and the adjacent inner continental shelf of Rio Grande do Norte. The study area is located between Presidente Costa e Silva and Nilton Navarro bridges, while the continental shelf area is located between the beaches of Mãe Luiza in the south and Redinha Nova in the north, approximately 10 km from the coast. Data on granulometry, carbonate, organic matter content, sedimentary facies and benthic foraminiferal distribution were studied. PCA (Principal Component analysis) and Cluster analyses divide the area into three parts. First part is the estuary, where fine to medium sands predominate, and foraminiferal assemblages show presence of pollution in the river channel. The second part is the central portion of the inner shelf, which has carbonate sedimentation and a great abundance of foraminifera. The third part is also located on the inner shelf, but has siliciclastic sediments and low abundance of foraminifera. Amonnia tepida are predominant in the estuary and Quinqueloculina lamarckiana in the shelf. The abundance of Amonnia tepida and the low concentration of the other species in the estuarine region probably revealed a high stress environment.

The Cretaceous led to the brittle reactivation of continental-scale Precambrian ductile shear zones and the development of rift basins in northeastern Brazil. These basins commonly exhibit subseismic structures, such as deformation bands. The objective of this study is to analyze the influence of early rift architecture and associated master faults on the occurrence and attributes of deformation bands. We used shuttle radar topography, aeromagnetic, and gravity data to unravel the rift structure and identify master fault segments. In addition, we used an unmanned aerial vehicle (UAV) and a field study to map deformation bands close to the main rift faults. Our results indicated that the Rio do Peixe Basin was formed along the reactivation of the Malta fault with four major fault segments and along the Portalegre fault along two major fault segments. Deformation bands occur in poorly sorted, medium to very coarse sandstones within ~70 m wide hanging wall damage zones at the master border faults. The deformation bands occur as single bands or clusters as far as 5 km from the master faults and are widespread in a structural high bounded by relay ramps. The deformation bands follow the strike or are oblique to the master rift faults. The kinematics of faulted deformation bands are consistent with those of extensional rift faults. In addition, a logarithmic decrease in deformation band frequency occurs away from the master slip surface. The deformation band frequencies peak close to the fault core with values as high as 22-48 bands/m. These observations indicate the influence of reactivated rift faults on the deformation band pattern and evolution, and they contribute to the prediction of the location, strike, and kinematics of deformation bands in continental extensional settings

The potengi estuary has undergone anthropic influences in the last decades, where these processes affected sediment distribution and bedforms. Changes in sedimentation patterns may result in habitat destruction, disturbances in physicochemical processes, changes in suspended sediment concentration, water eutrophication, and instability of estuarinesedimentary dynamics. This work aims to understand how estuarine sediments spread over decades and which factors control sedimentary dynamics in the Potengi estuary. To understand these changes, sedimentological and bathymetric data of the estuary were collected between 2003 and 2015 covering significant events such as: flooding, dredging and sewage treatment station. The recent sedimentological data show the existence of 10 faciological classes, with predominant siliciclastic facies along the main channel and the carbonate facies in the tidal channels, differently of the distribution sediments in 2003 that showed siliciclastic facies for the entire estuary. The main differences are granulometry reduction of the principal channel, representing a change from medium sand to fine sand, increase particle size in tidal channels, increase organic matter content throughout the estuary at levels greater than 3.0%, reduction the content calcium carbonate at the mouth of the Baldo channel and an increase of CaCO3 in the tidal channels. The bathymetric variation in the estuary between 2004 and 2014 is mainly due to the dredging carried out in 2010, with results the deepening of the channel with differences from up to 3m and increasing slope at the edges of the channel (7.5o - 22o). Changes in channel morphology after dredging show the reworking sediments in situ and adjustments in the river profile in relation to degraded areas. The estuary circulation is strongly controlled by tidal cycles affecting the bottom forms distribution and recent surface sediments. The comparison between data indicates a major marine influence in the carbonate sediments introduction among the estuary and the weak competence to export fluvial sediments and post-dredging in the short term.

The present research includes the integration of geophysical, seismological and geological data in the Northern domain of Borborema Province, Northeast of Brazil. This region presents areas with important records of neotectonic activities, and is seen as one of the most seismically active areas in the intraplate region of South America. The definitions in detail of the region and on which structures have been reactivated are still reasons for debate. The main aim of this study is to investigate the correlation between seismicity and the fabric of the Precambrian crystalline basement for the epicentral area of the Riacho Fundo and Samambaia faults. The faults present E-W and NE-SW trend, respectively, and exhibit a dextral transcurrent kinematics. The magnetic data were processed using the most varied filter applications in order to find the one that best correlated to contribute to the investigation of the reactivation of the basement fabric. Our investigation showed a correlation between the crystalline basement fabric and seismicity, which was done by comparing seismicity with interpreted magnetic lineaments. In the area of the Riacho Fundo fault, Granite Meruoca, the ductile fabric pattern indicates that the regional foliation is E-W-trending, correlating with the orientation of the epicenters zone. In the Samambaia fault region, the analysis of the basement fabric indicates that the regional foliation is NE-SW-trending, which coincides with the orientation of the epicenters and the quartz-chalcedony veins. In addition, in both regions, filters were applied to find the possible depths of the magnetic sources, associated with the faults and correlated with the regional hypocenters zone. With the Matched Filter, for the area of the Riacho Fundo fault we can obtain four depths: Deep ~ 2.7 - 7.2 km, Intermediate (1) ~ 1.2 - 2.6 km, Intermediate (2) ~ 0.4 - 1.1 km and Shallow ~ 0.0 - 0.3 km; the same was done for the area of the Samambaia fault, the four depths found for the magnetic sources were: Deep ~ 2.4 - 7.5 km, Intermediate (1) ~ 0.6 - 2.3 km, Intermediate (2) ~ 0.3 - 0.5 km, and Shallow ~ 0.0 - 0.2 km. Based on these data, we can observe that this relationship may indicate a reactivation of structures and the preexisting fabric for both areas.

The ediacaran plutonic activity consists of one of the most important geological features in the Borborema Province, NE of Brazil. In this context, the Serra da Acauã Stock (SAS) is inserted in the eastern portion of the Rio Piranhas-Seridó Domain (PSD), between the Currais Novos and Acari cities, state of Rio Grande do Norte. The integrated SAS study (geology, petrography, geochronology and geochemistry) may provide important information for a better understanding/discussion about ediacaran granitic magmatism in PSD. Cartographically, this stock has a surface area of 7km² divided into two facies: one fine to medium equigranular (subordinate) and a onother unequigranular medium to slightly porphyritic (predominant), with K-feldspar phenocrysts of 1.0 to 3.0cm. U-Pb (SHRIMP) determinations in zircon indicated an ediacaran age of c. 578 Ma for its crystallization, close to those already found for other ediacaran plutons in DPS. Petrographically the SAS rocks are hololeucocratic to leucocratic biotite-monzogranites (M = 1.3% -9.9%), with biotite being the main mafic (0.5% to 8.1%). Opaque minerals, titanite, allanite, apatite and zircon are earliest minerals. Geochemically the SAS rocks are similar, with a weakly peraluminous character (1.00≤A/CNK≤1.04), with normative corundum (0.11 – 0.59%) and transition signature between alkaline and calc-alkaline. The variation of the amount oxides and trace elements suggests the fractionation of plagioclase, biotite, titanite, apatite and magnetite during the crystallization of SAS magma. The Rare Earth Element (REE) diagram shows enrichment of the LREE relative to the HREE, with LaN/YbN ratios between 16.10 and 54.75, and negative Eu anomalies (Eu/Eu* = 0.66 – 0, 90) compatibles with plagioclase fractionation. Tectonic discriminant diagrams insert the SAS in the context of late to post-tectonic granites in relation to the Brasiliana orogenesis. The titanite-magnetite-quartz paragenesis in equilibrium, in addition to the processes of marttitization associated with magnetite crystals indicate relatively high fugacity (fO₂) during the evolution/crystallization of magma. Data related to the zircon saturation temperature added to the geochemical discriminant diagrams allow to associate these rocks with a regime similar to that of highly fractionated I-type granites of southern China. The total dataset allows correlating the SAS to the context of late to post-tectonics high-K calc-alkaline granites of PSD.

Bedforms are important morphological elements of shallow marine environments, working as major contributors to the sediment flow on the shelf. This research proposes to analyze the shallow-water bedforms morphodynamic on the continental shelf. We integrated single-beam bathymetry, Landsat 8 OLI image, swath bathymetry and sonography, scuba diving video and sediment samples. Two data acquisition campaigns were realized with a difference of two years. The subaqueous dunes field (SDF) is visible by satellite image. SDF is limited between 5 to 10 m depth, stretched to E-W. This field is composed by sand ridges parallel to the coastline in the west and oblique when near to the coast in the eastern part of the field. The SDF is shaped by the dunes amalgamation with crest to SW-NE direction. The dunes have 1 to 4 meters, with 400 to 1200 meters wavelength, measured from the single-beam bathymetry. The sand ridge flank facing coastline is straighter, on the other hand the side facing offshore has reentrances. On the coast, from east to west, there is the spit of Galinhos, the ebb tidal delta of the Guamaré tidal inlet, the Canto do Amaro barrier island system and the beach of Minhoto. From the mosaic generated by the sonar data, ripples were described, with SE-NW crests, superimposing the dunes. Scuba diving videos show symmetrical ripples, sometimes with red algae (rhodolites) in the trough. Four backscatter patterns were identified. This pattern is related to the four sedimentary facies found and change with the carbonate bulk content. The area is sandy covered, with variations of 10% to 80% carbonate. The integration of remote sensing, current and sedimentological data of distinct periods allowed to identify the morphodynamics of the bedforms and sedimentary cover in the shallow water. The coastal drift and the tide inlet of Guamaré influenced the current shape of the SDF. The difference in the data of bathymetry suggests a drift of the dunes to NW, also showing by its asymmetry. Ripples have SW drift; however, ripples superimposed the ridges of the dunes is drifting to NW. The passage of sediments between the dunes occurs through the trough. These ripples probably have the dynamics difficult by the presence of red algae in the trough.

The Potiguar Basin is located at the intersection between the east and equatorial Brazilian margins, covering areas of the Rio Grande do Norte and Ceará states. The sedimentary filling of this basin is represented by rocks that were deposited from Neocomian to Quaternary, during different tectono-sedimentary stages, being: Rift, Post-Rift and Drift. The last stage, in particular, designates a period of relative tectonic quiescence marked by more modest subsidence rates, which led to the deposition, in an open ocean context, of the Drift Supersequence. This supersequence is subdivided into the transgressive (lower portion) and regressive (upper portion) phases, by means of an important regional unconformity with upper Campanian age. The deposits of the regressive drift phase, target of this study, have their lithostratigraphy designated by the Agulha Group, which consists of the Barreiras, Tibau, Guamaré and Ubarana formations. The main purpose of this research was to perform a stratigraphic analysis of the regressive drift succession of the Potiguar Basin, from the perspective of sequence stratigraphy, aiming at a better understanding of its evolutionary process in the shelf, slope and basin regions. For this purpose, lithological information and gamma ray logs of five exploratory wells were used during a 1D analysis phase. Subsequently, the information from the previous phase helped to interpret seven seismic lines in the course of a 2D analysis phase. At end, the results of the 1D and 2D analyzes were integrated, leading to the individualization of five depositional sequences in the studied succession. In general, in more proximal portions, the two older sequences (1 and 2) were characterized by a preponderance of slope deposits, as well as by strongly progradational patterns. On the other hand, sequences 3, 4 and 5 have a more aggradational tendency and are represented by the sedimentation of shelf deposits. Concerning the Sequence 3, this is marked by a wide development of the carbonate sedimentation, whereas the Sequence 4 is characterized by a significant siliciclastic influx. The Sequence 5, in turn, has its depositional configuration defined by an important stage of global eustatic rise, which resulted in an extensive migration of the deposits from more distal portions to the shallower zones. Finally, in the deep marine context, the five depositional sequences show a similar framework, being denoted by the preponderance of hemipelagic successions, with the secondary presence of deposits associated with gravitational flows that occurs mainly in the two oldest sequences (1 and 2).

The ediacaran granitic magmatism of alkaline affinity (A-type) within the São José do Campestre (SJC) and Rio Piranhas-Seridó (RPS) Domains, in northeastern part of the Borborema Province, is represented by the Japi, Caxexa, Serra do Boqueirão, Serra do Algodão, Olho D’Água and Serra Negra do Norte plutons, and by the Flores stock. This work presents an integrated and comparative petrographic and chemical (whole-rock and mineral chemistry) study among these plutons, with the main focus on the revaluation of the intensive crystallization parameters (P, T, ƒO₂), in light of new geothermobarometric calibrations and crystallization modelling with the rhyolite-MELTS software. In order to provide a regional understanding of this magmatism, the results are compared with available data for chrono-correlated A-type granites within the Transversal Zone (TZ) Domain of the Borborema Province. Based on petrographic data, the plutons are divided in two groups: (1) plutons intrusive into the SJC Domain (Japi, Caxexa, Serra do Algodão, Serra do Boqueirão and Olho D’Água) that are made mainly of alkali-feldspar granites, syenites and syenogranites, with calcic amphibole and/or calcic and sodic-calcic clinopyroxene; (2) plutons that crop out in the RPS Domain (Serra Negra do Norte and Flores), comprising syeno- and monzogranites with biotite ± calcic amphibole and clinopyroxene (Serra Negra do Norte). Titanite, apatite, zircon and opaque minerals are the main accessories. Andradite is found in the Caxexa and Serra do Algodão plutons, and primary epidote in the Serra Negra do Norte. Overall, the studied rocks show well-defined alkaline to alkali-calcic affinities in lithochemical diagrams. They are iron-rich (ferroan) and have meta- to peraluminous character. The Serra Negra do Norte pluton differs by showing more magnesian compositions that approach those typical of calc-alkaline granites (cordilleran I-type). The mafic minerals follow the chemical signatures of their host-rocks. Clinopyroxenes vay from diopside and augite (Serra Negra do Norte and Japi) to hedenbergite and aegirine-augite (Caxexa, Serra do Algodão); amphiboles are mainly Mg-ferri-horblende, and the biotite is annite, with more magnesian compositions in the Serra Negra do Norte granites. The Caxexa, Serra do Algodão, Serra do Boqueirão and Olho D’Água plutons share petrographic and chemical similarities with peralkaline granites of the TZ Domain, whereas the Flores stock are akin to meta- to peraluminous A-type granites of the Alto Moxotó and Alto Pajeú terrains inside the ZT Domain. The Japi, and mainly the Serra Negra do Norte plutons are transitional, with chemical similarities sometimes with one group, sometimes with another. The revaluated thermobarometry reveals that the studied granites crystallized under pressures of 3.0–3.7 kbar (~11–14 km deep in the crust), except for those of the Japi pluton, with average pressures of 5.3 kbar (~20 km) that are akin to those found for the A-type granites in the Alto Moxotó and Alto Pajeú terrains. Crystallization modelling gave liquidus temperatures in the range 885–917 ^oC, and 818 ^oC for the Flores stock, and solidus between 660–700 ^o. When present, clinopyroxenes, amphiboles and biotite are formed between 813–822 ^oC, 728–751 ^oC, and 750–789 ^oC, respectively. Among the accessories, the geothermometer Zr-in-titanite yielded temperatures of about 780 ^oC (maximum of 830 ^oC). Crystallization took place under essentially oxidizing conditions for most of the plutons (+1.0 < Δ_QFM < +2.1; +0.4 < Δ_NNO < +1.5), except for the Flores stock formed under slightly more reduced conditions (Δ_QFM ≈ 0.0; Δ_QFM ≈ -0.6).

Methodological researches have pointed out severe limitations of Euler deconvolution (ED) to outline source shape. However ED has been extensively employed on field data to outline interfaces and estimate dips of faults and shear zones, evidencing a disagreement between theoretical and practical results of the tool. To reconcile this disagreement, we show that ED might help to infer useful information about source volume and dip, when it is applied to the reduced-to-the-pole anomalies caused by two types of body. In the first, the body might have uniform magnetization contrast but rough interfaces. The dip can then be grossly estimated from the solution cluster. In the second type, the body interfaces might be smooth but it has internal magnetization contrasts. Now, besides dip, one can delimit approximately the source volume from the solution cluster envelope. ED was also applied to field anomalies, which are caused by a curved-shape thrust zone and by a banded iron formation. These two field cases were considered as examples of anomalies caused by the described first and second types of bodies, being the ED results similar for each body type: for the thrust zone, the solution cluster follows its known geologic shape and allows to estimate dip variation whilst, for the banded iron formation, the solution cluster spreads out occupying a volume. For the latter case, a trial-anderror 3D modeling of the field anomaly was also performed to estimate the magnetization distribution and ED was applied to the fitting synthetic anomaly. The resulting solution cluster is similar to the one obtained with the field anomaly, showing the consistency of the ED results. From the obtained results, it can be conclude that ED does not really outlines source shape but that useful information about dip and volume might be indeed inferred.

Seismic illumination at each point of the interwell region can be defined as the maximum angle between the rays that pass through the point. Interfaces completely contained in the angular apertures can be imaged with first arrival travel time tomography (FATTT), but interfaces completely outside cannot be imaged even under regularized FATTT. We investigate if 2D acoustic full waveform inversion (FWI) can compensate for the lack of illumination. We use synthetic data generated with Ricker source wavelets with peak frequencies at 100 or 500 Hz, resulting in a small overlapping in the frequency bandwidths, so that a multiscale FWI approach is employed where the results with the 100 Hz dataset are used as input for the 500 Hz dataset. We investigate two FWI cases: in the first (FWI T), just the waves recorded at the opposite borehole are used whilst, in the second case (FWI T+R), the waves recorded at the two boreholes are used. For a single interface separating two media, the shape of the transmitted waveform varies significantly only when the interface is contained in the angular apertures. Accordingly, shot gathers for layered models with interfaces outside the angular apertures can be approximately reproduced with equivalent homogeneous media. As a result, in comparison with FATTT, both FWI cases give a mild improvement for models with interfaces inside the angular coverage, but cannot compensate for the lack of illumination. In this situation, minor resolution increases are obtained either with FWI T or FWI T+R cases. However, for models in the mixed condition where layers with interfaces inside the angular coverage are cut by a fault, FWI offers substantial improvements over FATTT, even if the fault plane is outside the angular coverage and FWI T is employed. In this mixed situation, resolution also increases when FWI T+R and source wavelets with a higher frequency content are used.

The São Francisco River is located in the northwest portion of Brazil and is the biggest river located entirely in Brazilian territory. This river had been affected by coastline retreat with times of a severe coast line erosion. Such changes in coastline had been attributed to anthropic changes such as dam’s constructions. The propose of this study is understand what is controlling the short-term changes that the coast line of this river is facing. For that, it was used three satellite images, the coast line was drawn for the periods of each cruise, 2009 and 2012 and for 2017. The drawn lines were made through Landsat 7 ETM+ scenes, for 2009 and 2012, and through Landsat 8 OLI scenes for 2017. It was calculated accretion and erosion as well as the accretion/erosion ratio for the areas of northeast and southwest from the São Francisco River Mouth. It was acquired sonographic and seismic data from 2009 and 2012 in order to identify bedforms changes during that period. The sonographic data was acquired through a Side Scan Sonar model 272-TD from Edgetech, and seismic were acquired from a parametric sub-bottom profiler model SES 2000 from Innomar Technologie. It was acquired hydrodynamic data from 2009 to understand the river behavior in its mouth, the equipament used was an Acoustic doppler current profiler (ADCP). Sediment sample from 2009 was collected with a Van Veen Grab in order to understand the sediment distribution along the area. Additionally, it was acquired historical data of rainfall, river runoff, ONI events and SACZ events to find correlations with coastal changes. The data analyze and process showed that the bed forms had not surfed significantly changes, indicating that the river are still transporting enough sediments to the coast. The SACZ events have more influence in rainfall regime than ONI events. The anthropic interference through rivers dams have more influence in coastline changes than rainfall regimes. We concluded that the São Francisco River is the main sediment provider to the coast, in this way, it will always find a new equilibrium when its discharge is controlled.

The Borborema Province is a geological and structural domain located in the Brazilian Northeast, which is limited to the South by the São Francisco craton, to the West by the Parnaíba basin, and to the North and East by a number of marginal basins. Its basement consists of Paleoproterozoic rocks and Archean nuclei, which underlay metamorphic supracrustal rocks with ages spanning the entire Proterozoic eon. Its structuration happened during the Brasiliano/Pan African orogeny, at the end of the Neoproterozoic, resulting in a complex orogenic system affected by ductile, metamorphic, and magmatic deformational processes. During the Mesozoic, the evolution of the Borborema Province was marked by extensional events that eventually led to continental breakup and the opening of the Atlantic Ocean. The separation formed a rift system in the Brazilian Northeast that was ultimately responsible for the formation of the marginal and interior basins that pervade the Province. After continental breakup, the evolution of the Province was characterized by episodes of intraplate volcanism along the Macau Queimadas Alignment 

(MQA) and tectonic uplift throughout the Borborema Plateau, which displays an elliptic topography and is located in the western half of the Borborema Province with maximum elevations of approximately 1200 m.

In order to understand the origin of the intraplate volcanism and uplift after the opening of the Atlantic Ocean, P-wave (and PKPdf) travel-times from teleseismic earthquakes were utilized to develop tomographic images of the upper mantle under the Borborema Province. About 120 events with magnitudes 5.5 and above, totaling over 1800 relative residuals, were used in the tomographic inversion. Those residuals were in turned mapped in 3D as P-wave velocity perturbations in the upper mantle under the recording seismic stations, through a tomographic inversion. Among the main features displayed by the tomographic images we find: (i) a relatively shallow low-velocity anomaly (< 150  km), located under the north easternmost corner of the continente and clos to the Cenozoic volcanism, and (ii) a high-velocity lithospheric mantle (<250 km) South of the Patos Lineament – approximately coinciding with the Southern half of the Borborema Plateau – when compared with the lithospheric mantle to the North. Those results suggest that the origin of the Cenozoic volcanism might be related to a relatively shallow termal at the corner of the continente, and that the Patos Lineament is a lithospheric-scale suture zone that separates contrasting mantle rheologies, with the more rigid rheolgy to the South of the Patos Lineament being responsible for the topographic elevation of the Borborema Plateau. The rigid lithosphere to the South of the Patos Lineament might also have affected the stress regime during the opening of the Equatorial Atlantic. The equatorial region marked the last phase of the continental breakup, contrasting with the stress regime in other segments of the Atlantic rift. A cold and rigid lithosphere at the Earth’s equator was independently postulated by other authors to explain the anomalous opening of the Atlantic Ocean in the equatorial region. However, theoretical calculations for the equatorial stress field developed in this work, demonstrate that a cold and rigid equatorial lithosphere would have resulted in a stress rotation opposite to that inferred from geological observations. Additionally, the pressence of a cold and rigid lithosphere contrasts with the tomographic results developed for the Borborema Province. Thus, a new tectonic model for the opening of the Atlantic Ocean in the equatorial region is proposed, in which Precambrian structures and lithospheric delamination – assisted by the St. Helena mantle plume – would have been responsible for stress transfer and rotation during the various rifting phases in the Equatorial region.

The phenomenon of coastal flooding in estuarine areas is studied worldwide to understand the risks generated by low reliefs and plans where human communities exist, economic activities and constant transformation of morphologies and ecosystems. Climate change is not new and forecasting impacts from sea level rise is a matter of concern to countries, as trends indicate greater frequency of flooding with greater depths and proportionate losses. This research was carried out in the Apodi-Mossoró estuary, in the northern coast of the State of Rio Grande do Norte, Northeastern Brazil, with the objective of analyzing the risks generated by the coastal flood related to the high altitudes of the mesotidal regime in an equatorial tropical hypersaline estuary with intense transformation by activities and human occupations. The research was based on geoprocessing techniques applied in remote sensing products with different spatial and temporal resolutions, observations of changes in land use and coverage, protected areas and wetlands, as well as the generation of information with precision and centimeter accuracy tracking with Global Navigation Satellite System and Remotely Piloted Aircraft to understand the hazards of flooding and areas under exposure, where it was necessary to work with digital photogrammetry procedures for digital surface model generation. The results point to saline activity as the main modifying agent of land use, resulting in the loss of permanent preservation areas, remaining 787.57 ha, and even so, approximately 1,907.09 ha of wetlands were lost in approximately 50 years . This picture contributes to the occurrence of coastal floods that affect 34.38 ha (16.29%) in the main city at the mouth of the estuary, in the city of Areia Branca / RN, interfering with the dynamics of more than 13 thousand people when the occurrence of floods by astronomical tide of spring tides of 3.8 meters combined with phenomena that rise 10 cm of the level of the sea. With the future trend of sea level rise, the flood area can reach 64.78 ha (30.69%) due to climate change. The flood reaches the special areas of planning of Areia Branca defined by its Master Plan, and in addition to the other areas affected, it is estimated economic damages close to R$ 597,438.68.

Ferriferous rocks occurrences in Rio Grande do Norte central region essentially correspond to small deposits without apparent economic potential. In contrast, during the last years, small deposits of this mineral has been well exploited in some areas of the region, especially within the Rio Piranhas-Seridó Domain. The iron formations occur as decimeters to tens of meters layers intercalated with the Jucurutu Formation gneiss, at the base of Seridó Group metavolcano-sedimentary sequence. They may be associated, but less frequently, with metamafic rocks hosted in the gneiss and possible orthoderived metamorphic rocks from Caico Complex. Systematic mapping at the scales of 1:100,000 (Lajes and Currais Novos geological maps) and mineral resources survey carried out by the Companhia de Pesquisa de Recursos Minerais (CPRM) identified a significant amount of mineral occurrences (registered 48 occurrences of ferriferous rocks). In this work will be performed a macroscopic and microscopic petrographic characterization of thin sections, bipolid and polished sections of banded iron rocks, besides the discussion of lithochemistry data by analyzing the major elements, trace signing and rare earth elements to defining protolith and tectonic environment, where appropriated, as well as the use of MEV-EDS to study the qualitative chemical composition of magnetites and amphiboles. Basically, these rocks are composed of quartz, iron oxides and hydroxides, amphibole (cummingtonite-grunerite and actinolite-tremolite series), fine- to medium grained and granonematoblastic texture, sometimes with compositional banding. They are formed by Fe2O3 content ranging between 46 and 59% and SiO2 content ranging between 33 and 50%. Petrographically it was identified two distinct groups: homogeneous ferriferous rocks and banded iron rocks. The lithochemistry permited to conclude that groups of homogeneous and banded iron rocks sometimes present a similar behavior, sometimes not. The bimodal rocks are mainly composed of Si and Fe, with small proportion of trace and rare earths elements. The chemical parameters indicate dominantly oxidant environment and groups of rocks at intermediate positions closest to the oceanic hydrothermal vents. As for the nature of the formation of the iron rocks, binary graphs with the relations between Th, Zr and Ti in ppm allowed to identify that they are chemically pure rocks, with few levels of terrigenous. While binary diagrams of SiO2 and Al2O3 in % of weight and Al-Fe-Mn ternaries indicate that all samples of ferriferous banded and granular formations form hydrothermal chemical-exhalation sediments. Specific diagrams for the identification of the tectonic environments for the formation of granular iron rocks and banded iron rocks studied in the Faixa Seridó indicate mainly oceanic chains located next to active continental margins transitional to island arches. The iron formation study is important not only because it is the most economical source of iron in the rocks, but is particularly essential to understanding the atmospheric evolution and to the oceanic chemical composition in the period of their deposition.

The northern outer continental shelf of the Rio Grande do Norte is a zone of physiographic, sedimentological transition and of physical and biological oceanographic processes marked by the eustatic variations of the Quaternary. The sedimentary evolution of these transition areas can be revealed through geomorphological and sedimentological data, for which the sonography method and the bottom sediment technique have been applied in geological and habitat mapping. In this study the side scan sonar was used to map an area of 413 km², parallel to the breaking of the platform, between Macau (to the north), and Ponta do Mel (to the east). As a result, 12 backscatter patterns (P1 to P12) were associated with 11 sedimentary facies (bioclastic and siliciclastic faceis), patches reefs that extend for more than 30 km parallel to the coast, and the paleovale of the Açu river that crosses all the region of the platform under study.The bioclastic sand facies with granules are predominant, related to the backscattering pattern P11, and is the main faceis responsible for the high percentage of organic matter and carbonate contents.The characterized sedimentary facies show a relationship between their distribution and the reefs mapped, indicating a migration of sediments to the west of the studied area, where the finest sediments are concentrated within the valley and among the reefs. Around the incised valley occurs the highest levels of carbonate and organic matter, this may be due to the geomorphological barrier formed by it that favors the circulation and the permanence of the nutrients in this region. However, this region does not concentrate the largest amounts of reefs, this may indicate excess nutrients capable of disfavoring its growth due to the competition for space generated with the sponges. The reefs were classified in patches reefs and elongated in the NW-SE direction, aligned for several kilometers. They are located between 30.68 - 33.91 m depth, with average values of 5 m for height, 135 m for length and 26 m for diameter. Reef alignment may be evidence of substrates that represent features subject to the effect of waves and tides, such as ancient coastal lines. The distribution of the sedimentary facies suggests that the sedimentation of the outer platform is constituted under a hydrodynamic regime of variable energy. Additionally, it was observed that the reef field serves as a trap for the sediments, this makes sedimentation distinct inside and outside the reef field. Thus, the sedimentation of regions above 30 m of depht are essentially bioclastic, and represent the most reef-rich portion of the shelf.

The integrated assessment of an aquifer intrinsic vulnerability constitutes an extremely important tool as a subsidy to the establishment of public policies for the preservation, protection and sustainable hydro-environmental use of an underground water source. In this aspect, the main purpose of this work was the elaboration of vulnerability mappings based on hydrogeophysical data, aiming at the identification and delimitation of subareas with different degrees of protection associated with different vulnerabilities of the Barreiras Aquifer in the lower course area of the Maxaranguape River, Northeast of Brazil. These mappings were elaborated using the following methodologies such as Longitudinal Electrical Conductance, GOD (G – groundwater hydraulic confinement; O – overlaying strata; D – depth to groundwater table) and Aquifer Vulnerability Indexes (AVI), which are based on lithological, hydraulic and geoelectric parameters, as well as the thickness of the unsaturated zone. The results show that the domains delimited by vulnerability indexes are approximately concordant with each other. In general terms, the moderate, high to extremely high vulnerability classes cover almost the entire area, delineating both the central and the northern and southern portions of the investigated area, according to values lower than 3 of log c and 5 mS, in the AVI and Longitudinal Conductance methodologies, respectively; and magnitudes higher than 0.4, according to the GOD methodology. Therefore, the study area exhibits a substantial susceptibility to the contamination of its groundwater, mainly due to the occurrence of sedimentary formations with high permeability and reduced depths of the water table, facilitating the percolation of possible contaminant loads towards the aquifer.

The Transbrasiliano lineament (LTB) is a NE-SW trending shear zone, with length of over 2700km in the brazilian territory. About 900km of the LTB occur in the precambrian basement of the Parnaíba Basin (BPar), inferred as a plastic shear zone with dextral strike-slip kinematics, on the basis of geological and geophysical data, as well as field observations in NW of Ceará and eastern Tocantins states. In the basin itself, reactivation of the LTB is expressed at the surface by NE-trending lineaments which correspond to faults or fractures intercepting paleozoic to triassic units of BPar. This dissertation addresses the structural signature and age of reactivations of the LTB in the southern region of the basin, east of Palmas (border region between Tocantins, Maranhão and Piaui states). In the crystalline basement, the dextral kinematics of LTB also displays a late, low temperature stage, probabbly of Ediacaran-Cambrian age, like observed at Northwest Ceará state. In the BPar lithostratigraphic units, reactivation events under brittle or hydroplastic conditions are recognized. In the studied region, an older event displays a sinistral transcurrent kinematics expressed as NE-trending deformation bands and faults of meso to macroscale, combined with oblique slip structures, either dilatational (including joints and normal faults) or conjugate/antithetic strike-slip or oblique slip-structures. Their orientations range from NNE to NNW, being observed in the Sambaíba, Pedra de Fogo and older formations. SE of Alto Parnaíba (Maranhão State), remarkable flower structures controling strata-thickening in Pedra de Fogo Formation attest syndepositional tectonic activity during the Neopermian. A second set of structures are extensional joints or oblique slip and normal faults associated with a N/NNE extension, overprinted in the eojurassic basic rocks of the Mosquito Suite and older units. Volcanogenic sandstones correlated to the Corda Formation overly basic sills south of Lizarda. A third set of structures, characterized by NE-trending normal or normal-oblique slip faults reflect a NW extension also observed along the eastern border of BPar, being correlated to the rifting event in the Brazilian Eastern Margin during the Eocretaceous. Finally, a fourth event, with more restrict occurrence, involves NE extension, being also observed in the Urucuia Group sandstones, sugesting a Neocretaceous age for both.

Large-offset transform faults/fracture zones characterize transform continental margins, which have been seldom investigated when compared to divergent and convergent margins. These faults influenced the segmentation and evolution of the transform margins. This study investigates the evolution of the Romanche Fracture Zone (RFZ) in the Equatorial margin of Brazil using bathymetric, magnetic, gravity, and reflection seismic data. The results of the present investigation indicate that the RFZ is an E-W-trending, ~70-km-wide zone marked by ridges 2.5 km above the surrounding topography. Magnetic anomalies that mark the oldest oceanic crust are at an angle of 26° and 30° clockwise south and north of the fracture zone, respectively, indicate that the first spreading centers were oblique to the main fracture zone. The anomalies rotated clockwise and shift from oblique to orthogonal to the transform at isochron 34 (83.5 ± 8 My). This rotation indicates that the influence of the continentaloceanic crust boundary is less pronounced as the anomalies become younger and a farther away from the continent. The RFZ behaved as topographic barrier, which prevented part of the sediments from the continent and shelf from reaching the northern part of the ridge. Normal faults form the border of the continental shelf and the borders of ridges and seamounts and they reach the upper younger layers, indicating that neotectonic reactivation. The orientation and geometry of the RFZ shaped the present-day geometry of the Brazilian margin, characterized by E-W- and NW-SE-trending sectors, and the evolution of the Pará-Maranhão, Ceará, and mainly the Barreirinhas basin.

This dissertation involves the digital imaging and modeling of a neoproterozoic microbialite colony from the outcrop of Fazenda Arrecife (BA), using the Ground Penetraring Radar (GPR) method and the application of "attributes". Concomitantly, a survey of repairs and an acquisition of radioactive profiles was applied, allowing the characterization of the sedimentary facies. Petrographic studies and chemical analysis (SEM/EDS and XRF) were used to identify a composition of the stylolithics levels that generate reflections in the GPR sections. The
"Instantantaneous Amplitude" attribute highlighted a microbialite community (low amplitude) which displays different signature pattern. The "Energy" attribute showed a similar result comparing to the "Instantaneous Amplitude", nevertheless, providing a greater visualization of the internal lamination of the columnar microbialite. The "Similarity" attribute emphasized the community boundary. The "Hilbert Trace/Energy" combination showed significant enhancement of the microbial growth boundaries than the "Energy" attribute. The attribute
"Hilbert Trace/Similarity" highlighted the internal structure of the microbial community. The described facies were described the microbialitic facies (MCme, MCm and MCma) and the tempestite facies (Cahm). The petrographic study shows minerals such as limonite and/or siderite, which corroborates with the chemical analysis results. The chemical analysis shows high Fe values to the stylolithic level, which causes the reflections observed in the GPR
sections, due to the electromagnetic contrast between the microbialite (ℇ = 6, 55) and the stylolithic levels (ℇ = 14,2). The 3D solid result properly represents a microbial community. The attribute application to GPR section applied in this dissertation allowed highlight the microbialite features non-observed in the original data. This application can be used in other geologic context.

The Brazilian Equatorial Margin (BEM) deep-water regions present important geological features, although few explored beyond continental shelf-break. The main objective of this study is to characterize seismically syn and post-rift sequences and some seamounts which are part of the Fernando de Noronha Ridge (FNR) in deep-water basins offshore northeastern Brazil. We used 2D post-stack high resolution seismic sections to distingue syn and post-rift tectonic phases. The syn-rift stage is marked by discontinuous and locally parallel reflectors with low amplitude and low frequencies, which are offset by normal faults in half-grabens. The post-rift stage is characterized by continuous-parallel reflectors with low to high amplitude and frequency. The volcanic intrusions affected syn-rift and post-rift sequences and partially confines deep-water basins deposits. That happened once the pre-existent material and the material deposited after the seamount rises were partially confined by continental slope and one or two seamounts. Some volcanic vents reach the ocean bottom and form dome-shaped features. Both volcanic episodes seem to have created volcanoclastic deposit marked by disorganized/chaotic seismic pattern with few continuous reflectors, indicating interbedded magma flows with sedimentary material. Seismic interpretation indicates two periods of volcanic activity: (a) Early Eocene to Late Miocene for seamounts and, (b) Neogene, for volcanic vents. Although deeper water regions can hold key points about the BEM formation and on future could represent oil and gas reservoirs, deep-water basins deposits remain poorly studied in this portion of BEM. In this sense, our paper provides a first insight about deep-water basin deposits on syn and post-rift stages and how they are affected by volcanism on area. 

This research presents the results of the interpretation of a 2-D seismic grid in the mid-western portion of the Parnaíba Basin, focusing on the pre-Silurian interval and the crystalline basement. Pre-Silurian grabens have been interpreted in the substrate of the basin, with implications to the subsidence controls and development of the syneclisis during the Paleozoic. The pre-silurian basin in the region of Balsas (MA) is compartmentalized by a structural high in two main depocenters. In the eastern sector of the study area, the pre-Silurian strata have an external wedge shape geometry which thickens towards an important N-S trending normal fault, about 100 km long, which bounds this depocenter to the east. In turn, the depocenter to the west of the structural high exhibits contractional structures. It was possible to individualize two seismic sequences in the pre-Silurian section. SEQ 1 is characterized by a package of high-amplitude parallel reflectors with regular thickness, which form a smooth arc over the structural high. SEQ 2 is characterized by low-frequency and low-amplitude reflectors, presenting as east-dipping parallel seismic facies. Both seismic sequences are deformed by folds and thrusts in the western sector of the study area, opposed to the extensional style observed to the east. It is proposed that the pre-Silurian interval corresponds to wedge-top deposits of a foreland system associated with the collision between the Parnaíba Block and the Amazon Craton along the Araguaia Belt, during the amalgamation of Western Gondwana in the Neoproterozoic.

Inversion in DC-resistivity is an ill-posed inverse problem because different realizations of the same model might satisfy approximately the same data fitting criterium. It is therefore necessary to use constraints to obtain unique and / or stable solutions to small perturbations in the measurements. However, in general, the introduction of constraints has been restricted to cases of differentiable constraints, which can be treated with local optimization algorithms. 1D and 2D modeling in DC-resistivity is computationally inexpensive, allowing the use of global optimization methods (GOMs) to solve 1.5D and 2D inverse problems with flexibility in constraint incorporation. Changes in the cost function, either in the constraints or data fitting criteria, can be easily performed, since each term of the cost function is properly normalized to allow the approximate invariance of the Lagrange multipliers. GOMs have the potential to support a computational environment suitable for quantitative interpretation in which the comparison of solutions incorporating different constraints is one way of inferring characteristics of the actual distribution of the underground resistivity. In this work, we developed: (i) comparison of the performances of the Simulated Annealing (SA), Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) methods to solve the 1.5D inverse problem in DC resistivity using synthetic and field data; (ii) an inversion approach based on particle swarm optimization (PSO) to solve the 2D DC-resistivity inverse problem; (iii) exploration of several constraints in the variation of log-resistivity, including spatial continuity in both L1 and L2 norms, total variation and sparsity constraints using discrete cosine and Daubechies bases. In addition, we explore the minimum inertia constraint, including the case of using the Earth’s surface as the target axis, to impose the concentration of resistive or conductive materials along target axes. The main results of the comparison for the 1.5D case are: a) all methods reproduce quite well the resistivity distribution of synthetic models, b) PSO and GA are very robust to changes in the cost function and SA is comparatively much more sensitive, c) PSO first and GA second present the best computational performances, requiring smaller number of forwarding modeling than SA, and d) GA shows the best performance with respect to the final attained value of the cost function and its standard deviation, whilst SA has the worst performance in this aspect. Equally important for both 1.5 and 2D cases, from the stopping criteria of the PSO algorithm results not only the best solution but also a cluster of suboptimal quasi-solutions from which uncertainty analyses can be performed. As a result, the interpreter has freedom to perform a quantitative interpretation process based on a feedback trial-and-error inversion approach, in a similar manner he/she has when using a friendly forward modeling software, being capable of driving the solution to incorporate his/her conceptions about the geologic environment, besides appraising data fitting and stability of the obtained solutions. We present both synthetic and field data examples for all inversion cases. 

A Bacia Potiguar, localizada na margem equatorial Brasileira, possui diversas rochas sedimentares que são afetadas por intrusões ígneas básicas cenozoicas, conhecidas como Magmatismo Macau. Dentre os efeitos mais proeminentes, relacionados a estas intrusões, temos a formação de buchitos, rochas pirometamórficas que ocorrem em altas temperaturas e baixas pressões, na fácies sanidinito. Por meio de revisão bibliográfica, observações de campo, petrografia, petrofísica, acesso a bancos de informações de trabalhos prévios na área e resultados da presente pesquisa, foi possível caracterizar e estimar os efeitos termais produzidos na auréola de alguns corpos hipabissais nesta bacia. As feições mais relevantes associadas às intrusões são: compactação, faturamento hidráulico, fusão parcial e recristalização das rochas encaixantes. De acordo com as ocorrências minerais registradas, interpretam-se de 800 a 1200oC e pressões inferiores a 0,5 kbar nas proximidades dos corpos ígneos. O modelamento térmico do plug São João registrou o efeito metamórfico até 150 m do contato com dissipação de calor total em aproximadamente 265 mil anos. Após o pico de temperatura, seguiu-se a fase de arrefecimento registrada com remobilização e precipitação de minerais de baixa temperatura em falhas, fraturas e geodos, derivados de reações com de porções sedimentares e fluidos metassomáticos / hidrotermais, com abundante silicificação e carbonatização.

A atividade sísmica do Nordeste do Brasil tem sidoalvo constante de estudos, uma vez que esta é região mais ativa do país.Contudo, algumas áreas possuem seus terremotos relacionados com ação humana, ouseja, são de caráter induzido. A barragem do Açu constitui um exemplo clássicode sismicidade induzida por reservatório e já foi alvo de diversos estudos.Recentemente, após um considerável período sem que houvesse atividade sísmicana barragem, o LabSis/UFRN registrou, por meio de uma estação regional, eventosrelacionados com o açude, o que motivou a instalação de uma rede local ao redorda barragem. A partir dos dados provenientes dessa rede, observou-se que aatividade sísmica está relacionada com uma nova área epicentral dento dabarragem. Os parâmetros hipocentrais dessa atividade foram determinados, bemcomo o respectivo mecanismo focal. Verificou-se que eventos estavamrelacionados com a reativação do embasamento em uma nova falha subvertical comorientação NE-SW subparalela a falha de São Rafael. Esses resultados foramutilizados na elaboração de um artigo científico, o qual discutiu a relaçãodessa sismicidade com a geologia da região e também com o nível de água doreservatório. O artigo mostrou que a difusão da pressão de poro foi o mecanismoque controlou o disparo da sismicidade induzida na barragem.

A química mineral de granitos, juntamente com revisão de dados químicos de rocha total e petrografia foram utilizados para determinar as condições de cristalização e as implicações na gênese de granitos Cálcio-alcalinos de alto K Porfiríticos. Seis corpos graníticos foram analisados: Monte das Gameleiras, Barcelona, Acari, Caraúbas, Tourão e Catolé do Rocha, localizados nos domínios Rio Piranhas-Seridó e São José de Campestre, NE do Brasil. Os plútons são representados por monzogranitos, texturalmente possuem fácies porfirítica compreendendo fenocristais de K-feldspato com tamanhos entre 5 a 15 cm. K-feldspato, plagioclásio e quartzo constituem a paragênese félsica e dominante; enquanto biotita e anfibólio representam os minerais máficos principais; titanita, minerais opacos, allanita, epídoto, apatita e zircão são os principais acessórios. Em relação ao índice de Shand o granito Monte das Gameleiras mostra-se mais metaluminoso, enquanto os outros seguem a transição metaluminoso a peraluminoso. Em diagramas discriminantes químicos estes se apresentam com caráter transicional (subalcalino). As análises de petrografia e química não expõe as diferenças dos granitos, porém os resultados de química mineral revelam as diferenças dos mesmos e podem ser divididos em dois grupos: a leste (Monte das Gameleiras, Barcelona e Acari) e a oeste (Caraúbas, Tourão e Catolé do Rocha). As razões Fe/(Fe+Mg) da biotita mostra um aumentam do grupo leste para oeste com valores de 0,48 a 0,64 e 0,66 a 0,92 respectivamente. As razões Mg/(Mg+Fe₂) do anfibólio diminui nesse sentido com valores de 0,40 a 0,57 e 0,06 a 0,31. As condições de cristalizações para os granitos a leste (Monte das Gameleiras, Barcelona e Acari) mostram pressão entre 4.2 kbar a 5.8 kbar, com profundidades que variam de 15,9 km a 20,5 km a uma temperatura entre 710 ºC a 734ºC e a oeste (Caraúbas, Tourão e Catolé do Rocha) com pressões de 5,4 kbar a 7,1 kbar e profundidades que variam de 20 km a 23 km a uma temperatura entre 729 ºC - 753 °C. Ambas as áreas, tanto leste como oeste foram gerados a partir de magmas oxidados. As profundidades das intrusões graníticas podem estar relacionadas aos deslocamentos de falhas e ao alto conteúdo de água e voláteis que permitem que o magma de alguns plutons atinja níveis mais rasos em relação aos outros. Os resultados mostram um aumento sistemático de temperatura e pressão de cristalização dos plútons de leste para oeste sugerindo um espessamento crustal nessa direção nos dois domínios geológicos pesquisados.

Nós estudamos a Bacia Potiguar Cretácea na margem Equatorial do Brasil para entender a geometria das grandes falhas e a influência da heterogeneidade crustal e o fabric estrutural preexistente na evolução da arquitetura interna bacia. Estudos anteriores apontaram que o rifte é um meio graben assimétrico alongado de direção NE-SW. Para determinar o deslocamento máximo (D_máx) e comprimento (L) dos principais segmentos de falha de borda do Rifte Potiguar foram usados sísmica 2D, dados de poços e modelagem gravimétrica 3D. A modelagem gravimétrica 3D foi parametrizada com os dados de poços e interpretações das seções sísmicas. O grau de incerteza do modelo gravimétrico foi da ordem 10% aos dados sísmicos e de poços. Através das curvas de crescimento de falhas foi possível dividir as falhas de borda do rifte em quatro segmentos principais, os quais forneceram valores D_máx/L da mesma ordem de grandeza. As curvas de crescimento de falhas sugerem que um mecanismo tectônico uniforme regional teria influenciado o crescimento dos segmentos dessas falhas.  As variações dos deslocamentos máximos ao longo dos segmentos de falha indicam que estes segmentos se desenvolveram de forma independente durante o início do rifteamento e, posteriormente, foram unidos por ligações rigídas e flexíveis. Este último, chegou a formar uma rampa de alívio entre as falhas de Baixa Grande e Carnaubais. Nos pontos de interligação entre falhas as taxas D_máx / L são mais elevadas devido à interferência do crescimento dos segmentos de falha adjacentes. A evolução do Rifte Potiguar foi dividida em cinco etapas com base nas relações D_máx/L, que foram correlacionadas com as principais fases tectônicas da separação entre a América do Sul e África no Cretáceo Inferior.

The mapping of features in the subsurface can be established in detail by the seismic using sub-bottom profiler, high resolution hydroacoustic equipment. The study area is located in the Açu river, bounded by its estuary, northern coast of the Rio Grande do Norte state, NE Brazil. Locally, the estuary is inserted in a coastal environment consisting of: fluvio-marine floodplain, mangrove ecosystem, sandy banks, dune fields, spits and sandy beaches. This study aimed to characterize the depositional and erosional features from Açu River estuary, through the acquisition, processing and interpretation of high-resolution seismic data and cores. Using the XStar sub-bottom profiler (chirp), with frequency range between 0.5 to 7.2 kHz, were acquired seven seismic profiles (four horizontal and three parallel to the river course), totalizing approximately 16 km of seismic acquisition. The cores were done in seven different points along the estuary, using two drilling methods: vibracore and percussive. The length of the cores varied between 0.42 m and 4.27 m. Processed seismic data showed excellent quality and allowed the visualization of several architectural elements characteristic of estuarine deposits, such as: lateral accretion deposits, channel concave erosional base, infill deposits. Moreover, subaqueous dunes and flat bottom bedforms were also observed. Additionally, well market reflectors were interpreted as: (1) erosional truncation surface; and (2) possible Pleistocene-Holocene contact. The cores showed an intercalation between clayey and sandy layers (ranging from very fine to course) which allowed the correlation between geophysics and geology on the study area

The target area of this research is the Maxaranguape River lower course, located on the east coast of Rio Grande do Norte state, and particularly the hydrogeological domain Barreiras Aquifer. This study aimed to analyze the influence of regional structure in the geometry of the aquifer in the study area (taking into account thickness variations), in order to make an optimized calculation of local hydrogeological reserves in that area.

The methodology was based on the use of morphotectonic and lithostratigraphic analysis techniques, in well profile correlation, as well as hydrogeological and geoelectric analysis (Vertical Electrical Sounding - VES). The geophysical method of electrical resistivity was adopted in order to infer thickness values of the aquifer and depth of the basement. It were carried out 17 SEV with maximum aperture of current electrodes (AB) of 1200 meters, distributed so as to cover the entire study area, although primarily seeking to obtain data for subareas with little or no well information. Hydro-stratigraphic and lithologic data from 21 wells profiles were integrated with VES  data, 5 hydrogeophysical profiles were generated to define downthrow and  a geomorphological analysis was performed, which aimed at the structural characterization of the area with emphasis on aquifer compartmentalization. The morphotectonic analysis used the topographic (SRTM) and hydrographical data to support the structural characterization taking into account the lack of outcrops with specific features in the area. Topographic data are presented as a map of residual topographic anomalies, with defined topographic lineaments. Hydrographic data underscore preferred directions of fluvial channels and anomalies of this hydrogeophysical network with abrupt deflections of drainages and alignments of other surface features such as springs. The results of this analysis enabled to draw up a morphotectonic lineaments map, arranged according to the prevailing NE and NW directions. The results of this analysis enabled the development of a map of morphotectonic lineaments, arranged according to the prevailing NE and NW directions. The hydrogeophysical profiles, obtained from geoelectric inverse models and well data, were prepared to intercept the lineaments, emphasizing saturated thickness values ranging from 19 to 66 meters, and featuring some of these lineaments as faults.

The hydrogeological reserves were evaluated considering 18 subareas associated with blocks resulting from structural compartmentalization. Therefore, the saturation reserves are the order of 8.7x10⁸ m³, considering average saturated thickness for each subarea and 7.6% average effective porosity.

A borda oeste da Bacia do Parnaíba é definida por superfícies de não conformidade (em geral, na base do Grupo Serra Grande) e é acompanhada por um marcante sistema de lineamentos N-S, a leste do contato com o embasamento.  A distribuição das unidades litoestratigráficas nesta região também segue a orientação N-S, diferindo do arcabouço geral ovalado da bacia. Esse padrão N-S corresponde a uma estrutura grabenforme já abordada na literatura e esboçada nas cartas geológicas da CPRM. A oeste do gráben, dominam as ocorrências da Formação Pimenteiras, sendo que o Grupo Serra Grande ocorre com maior expressão na porção sul do gráben, o que sugere para o mesmo uma terminação mais rasa, nesse sentido. No gráben e suas bordas, afloram unidades mais jovens (tais como as formações Motuca e Sambaíba, eo-mesotriássicas), em contatos normais ou balizados por falhas normais ou normais oblíquas que ocasionam a omissão de algumas formações no empilhamento estratigráfico. No alto estrutural a leste, e ainda na região sul (Palmas-Miracema do Tocantins), o Grupo Serra Grande e o embasamento cristalino afloram soerguidos por essas falhas, já no interior da bacia. A análise de imagens SRTM auxiliou na cartografia dos lineamentos e, acoplada aos mapas pré-existentes, os limites do gráben. A orientação N-S das falhas envolve uma variação de 20º-30º para E ou W. Considerando que, a oeste, a Faixa Araguaia também exibe orientação N-S, fica patente o controle das anisotropias do embasamento sobre a estruturação desta borda da bacia. Na região norte do gráben, lineamentos E-W/ENE que controlam as ocorrências de diabásios e basaltos eojurássicos da Suíte Mosquito claramente interceptam as estruturas do gráben. Na área do gráben e adjacências foram observadas em campo falhas de regime normal ou normal sinistral, dominando a sua estruturação controlada por distensão NE. A idade mínima para a formação do gráben é estimada no Eo-Mesotriássico, com base nas relações entre as estruturas descritas e as unidades litoestratigráficas. As estruturas de distensão NNW eojurássica na Suíte Mosquito, e falhas normais ou transcorrentes exibindo distensão NW, são mais jovens sendo tentativamente correlacionadas aos eventos de abertura do Atlântico Central e Sul, respectivamente. O presente trabalho constitui uma contribuição do Projeto Bacia do Parnaíba, objeto de contrato entre a UFRN/PPGG e a empresa Chevron Brasil.

The Parnaíba Basin occupies a large area in the NE portion of Brazil, covering several states. It is a Paleozoic syneclise that contains records from the formation and break-up of the Gondwana supercontinent. The basin is supported by a crystalline basement developed after the collision between the Amazonian and Brazilian platforms. During the Mesozoic break-up of Pangea megacontinent, which contributed to the opening of the Atlantic Ocean, intrusive igneous (dykes and sills) and extrusive rocks took place in the Parnaíba Basin. In the stratigraphic context, those igneous rocks were divided into two units: Early Jurassic Mosquito and Early Cretaceous Sardinha formations. The main objective of this research is regional geophysical mapping of these magmatic bodies based on aeromagnetic data and self-organizing map technique (SOM). The Matched Filter was applied in order to decompose the Total Magnetic Intensity anomalies (TMI) of the basin in their components related to magnetic sources at different depths: Deep (DMF), Intermediate (IMF), and Shallow Magnetic Fields (SMF). As the IMF anomalies mainly present contributions caused by magnetic sources at shallower depths in the upper crust, characteristics of such magmatic bodies, spectral filtering techniques (Analytic Signal Amplitude and Vertical Derivative) were applied in the IMF data in order to enhance the geophysical response of these magnetic sources, increasing the spatial resolution of the investigative method. Based on high amplitude and short wavelength anomalies, magnetic domains and lineaments were delimited in aeromagnetic maps and correlated with the possible causative bodies. Thus, the correlation of the geophysical maps with SOM solutions and the geological map allowed to propose an interpretive map with the surface distribution of magnetic anomalies associated with Mesozoic Magmatism in the Parnaíba basin. The results indicated that the Mosquito Magmatism has great occurrence at the western and southern basin edges and the Sardinha Magmatism is located at the central-eastern and northeastern parts. Magnetic susceptibility data, measured in the magmatic rocks, permitted individualizing the Mesozoic Magmatism.The Sardinha Formation displays average magnetic susceptibility of 25.2 x 10^-3 SI, about two times higher than the values of 11.46 x 10 ^-3 SI obtained to Formation Mosquito, revealing a compositional differentiation of these two magmatic events. Associations between seismic sections, magnetic data and geological map showed that the high amplitude anomalies in the Analytic Signal and TMI maps are associated with sills and dykes intruded usually within Balsas, Canindé and Serra Grande groups, and are significantly influenced by outcropping or at near-surface buried igneous rocks. Finally, the directions of the magnetic lineaments revealed that ENE-WSW and NNE-SSW oriented rifts, associated with the break-up of West Gondwana, and E-W and NE-SW structural trends, associated with Transbrasiliano Shear Zone, exercised structural control over the Mesozoic Magmatism of the Parnaíba basin.

The southeast border of the Parnaíba Basin (BPar), which follows the borders between the Piauí, Bahia and Pernambuco states, is characterized by an expressive NE trend parallel to the one of the Transbrasiliano Lineament, as well as a narrowing of the outcropping belt of the Silurian-Devonian formations, as compared to the situation in the east basin border.  The evidence of a structural control in this basin border was analysed interpreting hillshade images obtained from radar imagery. NE-trending photolineaments were highlighted in the crystalline basement and in the sedimentary cover, as well as in the contact zone between these domains. An integrated analysis of macroscale (radar and multispectral images) and mesoscale (outcrop data) structures, lead to the characterization of three deformation events on the basis of their orientation, kinematics and chronology. Dn structures were recognized in the crystalline basement and molassic sequences of Araçá and São Julião basins, being correlated to same context of the Jaibaras Group, in NW Ceará, of Ediacaran-Cambrian age. This deformation event is related to a retrometamorphic, plastic-brittle late stage of Brasiliano mylonite zones. Its signature includes NE-trending dextral transcurrent shear zones, as well as acid veins filling dilational C bands and E-W extension joints. Dn+1 deformation corresponds to a new stage of dextral movement along the NE-trending structures, accompanied by normal faults and extension joints oriented WNW to E-W, in this case overprinting the Silurian-Devonian formations. Dn+2 deformation is characterized by normal faults, basic dykes (correlated to the Eocretaceous Sardinha Suite) and siliceous veins (filling anisotropy in rocks), all of them following a NE-SW trend. The NE-trending faults may occur in the contact between basement and the sedimentary cover, or inside the basin. This event resulted from a NW-SE extension, analogous to the one recognized further east in the Northeast Brazil Interior Basins, associated to the South Atlantic rifting.

This paper analyzes different types of karst landforms and their relationships with fracture systems, sedimentary bedding, and fluvial processes. We mapped karst features in Cretaceous carbonates of the Jandaíra Formation in the Potiguar Basin, Brazil. The study area is a semi-arid region, with low annual rainfall (600mm) and high evaporation (2.000mm). We used high-resolution digital elevation models acquired by Light Detection and Ranging (LiDAR) and aerial ortophotographs acquired by unmanned aerial vehicle (UAV). This study focuses on surface and near surface process and grouped karst evolution into four stages. Fractures were opened by dissolution, which form vertical fluid pathways during stage 1 in a centimetric to metric scale. The most pervasive set of fracture concentrates the dissolution. Coeval intrastratal and interstratal dissolution occurred along horizontal layers, which bound dissolved fractures. This conduit system acted as pathways for water flow, which caused advanced leaching. The enlargement of conduits in subsurface contributed to the collapse of blocks, generation of sinkholes, and caves expansion in stage 2. During stage 3, propagation of horizontal and vertical dissolution along fractures and layers cause coalescence of sinkholes and capture of small streams. Fluvial processes dominate karst dissolution during stage 4, where alluvial sediments that caps the carbonate karst surface and fill caves and sinkholes along the valley. Tectonic and sedimentary bedding control all stages of karst evolution and resulting structures and landforms formed during these stages coexist. Comparisons with GPR, borehole and seismic surveys in sedimentary basins indicate that these structures are preserved after burial.

The study area is located in the region of Baraúna-RN city, extreme West of the Potiguar basin, RN. It covers an area of 1290 square kilometers, including the city of Baraúna (urban and rural zone), and the part of the cities of Quixeré-CE and Mossoro-RN. The Jandaíra aquifer constitutes the hydrogeological unit and it is the object of this work. It is an aquifer of carbonate rocks used in the water supply of urban and rural population, especially in the production of irrigated orcharding. The Jandaíra aquifer is a karst-fissure aquifer with a large variability in hydrodynamic parameters that is attributed to its heterogeneous and anisotropic character, with frequent features discontinuities. The aquifer is quite affected by overexploitation attributed to agricultural activities, but also is influenced by the periodic droughts that occur in the region. The study is being accomplish to evaluate the hydrogeological behavior of the aquifer Jandaíra with a view to the management of the available water resources, for this, it will be evaluated its conditions of use, the character of the groundwater flow and the hydrodynamic parameters, influence of the drought and calculation of recharge, followed by the proposition of the conceptual model. 

Analog modeling has been used since the XIX century to simulate geological structures in order to understand the mechanisms that control its geometry and kinematics. The use of this tool in the oil industry, to help seismic interpretations (mainly to search for structural traps), helped to spread the use of this tool in the literature. Studies involving basins inversion are developed to improve understanding factors that influence the reactivation of pre-existing structures as well as their geometry. In this work, we analyze the construction of the structural architecture of a fault system that underwent positive inversion, and analyzed the relationship between the generation of new faults and reactivation of pre-existing normal faults during a contraction event. In addition, the behavior and distribution of strain along the deformation process ware performed based on images obtained and processed by Particle Image Velocimetry (PIV) system. Two series of experiments were developed: i) Series I: We analyzed the generation of fault sets associated with a main lístrica fault and their reactivation during a kinematics inversion event. Two types of models were performed: one with lístrica fault, orthogonal to the direction of tension and compression (IA series), while in the other the lístrica fault was oblique ("α" = 80) (IB series). The final structural configuration after inversion showed major fault and some of the normal faults (delimiting the grabenforme structure) reactiveted. Thrust and backthrust were developed from the basal portion of listric fault, or in the upper part of the model, propagating towards the base of grabenform structure; ii) Series II: We analyzed the generation of faults associated with the formation of a planar master fault, orthogonal to the direction of both tension and compression. In these experiments, the role of rheology during normal faults reactivation was analyzed. Three types of experiments were done varying the materials of the pre-tectonic sequences: only sand (IIA series); sand and gesso (IIB series); and sand and clay (IIC series). These experiments displayed the final architecture with normal faults completely or partially reactivated, and the developed thrusts and backthrust sliced up the basal portion of the grabenforme structure. The PIV data showed that during the first stages of compression, deformation was absorbed mainly by rearrangement of the granular material (compactation) and only after this process fault reactivation (or new fault) occurs. During deformation, some faults alternated intervals of activity and inactivity.

The evaluation of the hydrodynamic and hydrochemistry behaviour of the aquifers in areas under the influence of the oil exploration activity, are essential to the protection and management of the groundwater resource.

The aim of this study was to analyse the relationships between the hydraulic loads of Açu and Barreiras-Jandaíra aquifers in the area of Fazenda Belém, sector west of the Potiguar basin and its implications on the quality of groundwater.

The potentiometric surfaces of the two aquifers systems for different periods, since its original state, before the influence of the oil exploration activity, until the present day were set, as well the variations in hydrochemistry of these units, throughout this period.

With this information it is possible to affirm that the Açu and Barreiras–Jandaíra aquifers correspond to individual aquifers systems without hydraulic communication with each other. The distinct water chemical classes of the two aquifers confirm the isolation between them and indicating the absence of water mix between the two systems, since its original state until the present.

The study has identified a local fall in the potentiometric surface of the Açu aquifer, which points to the need to propose measures of control, through the continuous monitoring of water levels of the aquifer and the quality of its waters

Processos endógenos recentes proporcionam dinâmica à litosfera e geram as mais variadas formas de relevo, mesmo em áreas de margens continentais passivas, como é o caso da área de pesquisa deste trabalho, localizada no Nordeste brasileiro. A reativação das estruturas do embasamento pré-cambriano, após a separação entre a América do Sul e África no Cretáceo, teve um papel importante na evolução de suas bacias, o que proporcionou formas de relevo variadas. Estas características morfodinâmicas podem ser facilmente percebidas nos sedimentos de borda das bacias marginais, que apresentam fortes indícios dessas reativações. O objetivo deste trabalho é investigar a influência dos processos morfotectônicos na estruturação da paisagem nos sedimentos da Bacia Paraíba. Para tanto foram utilizados dados aeromagnéticos de alta resolução, imagens da Shuttle Radar TopographicMission-SRTM, dados geológicos estruturais, dados de poços profundos e dados geológicos de campo. Nos resultados foi observado que algumas estruturas conhecidas no embasamento da Bacia Paraíba coincidem com os lineamentos magnéticos e topográficos interpretados como reativações de falhas do Pós-Mioceno. A atividade neotectônica ocorrida na Bacia Paraíba teve a capacidade de reorganizar a deposição dos sedimentos e de dominar os padrões das formas de relevo. Dados estruturais adquiridos nas unidades litoestratigráficas mostram evidências de atividade tectônica associada à deposição e erosão de sedimentos do final do Cretáceo até o presente. Isto indica que a deposição dos sedimentos pós-cretáceos foi influenciada por reativações de estruturas do embasamento pré-cambriano nesta porção da margem continental brasileira.

O Estado do Rio Grande do Norte é privilegiado pela existência de quatro Províncias
Espeleológicas distribuídas da seguinte forma: Província do Mato Grande, situada ao
norte do estado; Província da Chapada do Apodi, na porção oeste; Província Seridó,
situada ao sul do estado; e a Província do Alto Oeste, no sudoeste do estado. Este
trabalho abordará a influência de feições estruturais em relação à morfogênese de
ambientes cársticos, bem como sua relação com porosidade e permeabilidade dos
carbonatos da formação Jandaíra. A formação Jandaíra faz parte do Grupo Apodi, é uma
unidade litoestratigrafia Turoniana-Campaniana pós-rifte na Bacia Potiguar e encontrase
no contato inferior concordante com as rochas siliciclásticas igualmente aflorantes da
Formação Açu. Para um melhor resultado na pesquisa, foi utilizado o VANT (Veículo
Aéreo Não Tripulado). O VANT pesa cerca de 900 gramas e com 50 centímetros de
largura, esse dispositivo alcança uma altura máxima de 400 metros e seguindo um plano
de voo consegue fazer várias imagens e após um processamento, obtém-se um mosaico
com todas as fotos e assim uma imagem área de alta resolução é gerada. Foram
exploradas 17 cavidades no Lajedo do Rosário, das quais foram selecionadas apenas as
cavidades imageadas pelo VANT no total de 8 cavidades distribuídas pelo o lajedo. A
área de estudo foi fragmentada em três domínios e escolhida com base na necessidade
de investigar o comportamento dos diferentes sets de fraturas em superfície e
subsuperfície, que possuem quatro padrões distintos de trend de direção preferencial,
são eles: N-S predominante na porção central, E-W que são as fraturas bem marcadas na
porção oeste da área e por fim, pares conjugados na direção NE-SW e NW-SE na
porção leste. A porosidade é evidente na interconexão de duas fraturas, pois o ponto de
encontro entre ambas sofre colapso, gerando uma feição negativa, ou seja, uma
cavidade. Vale ressaltar que a porosidade é bastante influenciada pelo regime tectônico
da região, pois é bem visualizada em diferentes escalas, tanto na escala de afloramento
quanto na escala vista na imagem do VANT. Além disso, foi observado em superfície,
os lajedos totalmente fraturados e basculados onde o mesmo apresenta diferentes
feições cársticas, de padrões tectônicos e atectônicos.

A modelagem física é uma ferramenta cada vez mais utilizada para melhorar o entendimento da formação e desenvolvimento das estruturas geológicas. O crescimento na utilização dessa ferramenta é impulsionado principalmente, mas não exclusivamente, pela indústria do petróleo onde a análise estrutural é importante para a definição da geometria das estruturas que possam constituir armadilhas para o hidrocarboneto.

O presente trabalho teve como objetivo o estudo da influência do contraste reológico na nucleação e desenvolvimento de falhas e fraturas em contexto de bacias ortogonais e sub-bacias conjugadas oblíquas à direção de distensão. Os materiais utilizados incluem pó de gesso, microesferas de vidro, argila seca e areia quartzosa. Alguns experimentos foram realizados com o acompanhamento do PIV (Particle Image Velocimetry), instrumento que registra a movimentação das partículas granulares a cada instante deformacional.

Duas séries de experimentos foram realizadas: i) A série MO representa os experimentos que geraram uma bacia ortogonal à direção de distensão. Vários experimentos foram realizados, variando-se os materiais, a espessura dos estratos, além da presença, em alguns experimentos, de sedimentação sintectônica. Verificou-se que há diferenças de comportamento das falhas geradas nas camadas de materiais reologicamente distintos. As camadas de pó de gesso comportaram-se de forma mais competentes do que as camadas de areia quartzosa e microesfera de vidro, levando à formação de um maior número de falhas. De forma geral, as falhas nas camadas de gesso foram nucleadas a partir de fraturas e geraram blocos com a clássica geometria em dominó. A passagem das falhas de um estrato menos competente para um mais competente é marcada pelo aumento acentuado do mergulho. Brechas cataclásticas são desenvolvidas em algumas falhas, mas com histórias de desenvolvimento diferente, dependendo da configuração inicial do modelo. ii) A série MO-S2 representa os experimentos com a formação de bacias conjugadas, obliquas à direção de distensão. Um experimento constituído apenas de estratos de areia quartzosa foi comparado com outro contendo contraste reológico entre os estratos. No experimento sem contraste reológico dois depocentros importantes se desenvolveram junto às falhas das bordas das bacias ao contrário da sequência com estratigrafia mecânica. Embora ambos apresentem sistemas de falhas oblíquas, no modelo estratificado as falhas são mais numerosas, maiores e desenvolvem-se de forma mais rápida (com menor intensidade de distensão).

Este estudo foi realizado na plataforma interna equatorial brasileira adjacente ao Rio Grande do Norte, entre a região de Porto do Mangue e Galinhos, tendo como principal objetivo a caracterização dos sedimentos biogênicos, especialmente os foraminíferos e ostracodes coletados na superfície do fundo marinho. A metodologia utilizada envolveu procedimentos padrões de levantamentos bibliográficos, processamento de amostras em laboratório e identificação, em lupa binocular e microscopia eletrônica de varredura (MEV) dos foraminíferos e ostracodes segundo gênero ou espécie. Análises estatísticas multivariadas e estudo dos índices ecológicos foram aplicados no estudo de foraminíferos. Com o objetivo de um melhor entendimento e interpretação dos resultados a área foi dividida em três perfis perpendiculares a linha e costa, desde a plataforma interna até o talude: o perfil 01 (a leste, próximo a Galos), o perfil 02 (centro, próximo à cidade de Macau) e o perfil 03 (a oeste, próximo a Ponta do Mel). As condições ambientais influenciam diretamente no desenvolvimento dos organismos. Na região de estudo observa-se uma homogeneidade relativa para as distribuições horizontais de temperatura, verificando-se para a superfície (mínima de 24º C, e máximas de 29ºC a 35ºC) e para a região localizada nas proximidades do fundo (mínima de 5,2 ºC, e máxima de 28,8 ºC). Os resultados indicaram o predominio dos gêneros de foraminíferos bentônicos com pouca ocorrência planctônica. Os gêneros bentônicos observados em maior abundância foram Quinqueloculina, Textularia , Globigerina e Pyrgo, respectivamente; Quinqueloculina, Textularia, Pyrgo, Ammonia, Elphidium, Pseudononion, Peneroplis, Bolivina e Poroeponides, respectivamente, ocorreram com maior frequência. Com menor frequência foram descritos Amphistegina, Arcaias, Bigenerina, Cibicides, Cassidulina, Amphicorina, Cornuspira, Paterina, Hopkunsina, Oolina, Uvigerina, Fusenkoina, Nonionella, Amphisorus, Wiesrella, Reussella, Reophax, Nodosaria, Marginulina e Cyclogyra. Também foram Entre os Foram identificados seis gêneros de ostracodes: Puriana variabilis/P. convoluta ?, Loxoconcha sp, Bairdiidae, Xestoleberis sp, Hemicytheridae e Ruggiericythere sp. Os grupos de organismos encontrados na plataforma atual apresentaram composição química principal de Ca, C, O, Na, Cl, Al, Mg e Si. A proporção destes elementos químicos pode variar de acordo com o tipo de sedimento biogênico, sendo as maiores quantidades identificadas de Ca, C, Cl, Na e O. A datação absoluta pelo método carbono 14 indicou que as gerações de sedimentos de colorações diferentes (claras e escuras), correspondem a uma única idade, entre 3 e 6 mil anos AP, relacionados ao Quaternário. Estes dados irão complementar informações a respeito dos sedimentos biogênicos existentes atualmente na plataforma continental brasileira, especialmente na região nordeste, onde há carência de estudos nesta linha de pesquisa. 

A atividade plutônica ediacarana, relacionada a orogênese Brasiliana/Pan-Africana, constitui uma das mais importantes feições geológicas na Província Borborema, representada em sua extensão por inúmeros batólitos, stocks e diques. O Plúton Granítico Serra da Rajada (PGSR), principal objeto desse estudo, situado na porção central do Domínio Rio Piranhas–Seridó representa um exemplo dessa atividade, sendo objeto de estudos cartográfico, petrográfico, litogeoquímico e geocronológico. Suas rochas são individualizadas em duas fácies, sendo a fácies granítica descrita como monzogranitos constituídos por K-feldspato, plagioclásio (oligoclásico-An_23-24%), quartzo e biotita (máfico principal), tendo como minerais acessórios opacos, titanita, allanita, apatita e zircão. Clorita, mica branca e carbonato são minerais de alteração. A fácies diorítica compreende rochas formadas por quartzo diorito contendo plagioclásio (fase mineral dominante), quartzo e K-feldspato. Biotita e anfibólio são os minerais máficos dominantes, e titanita, minerais opacos, allanita, zircão e apatita são os acessórios. Contudo, os trabalhos de cartografia geológica também identificaram na região a presença de outras unidades litoestratigráficas, descritas como gnaisses e migmatitos indiferenciados com lentes de anfibolitos relacionados ao Complexo Caicó (Paleoproterozoica) e rochas metassedimentares do Grupo Seridó (Neoproterozoico) compostos por paragnaisses com lentes de calciossilicáticas, muscovita quartzitos e biotita xistos (respectivamente formações Jucurutu, Equador e Seridó), os quais são as encaixantes para as rochas do PGSR. Ainda foram identificados diques de leucomicrogranito e de pegmatitos, ambos relacionados ao final do magmatismo Ediacarano, bem como depósitos colúvio-eluviais e aluvionares relacionados ao Neógeno e Quaternário, respectivamente. Dados litogeoquímicos, na fácies granítica do PGSR, evidenciam rochas bastante evoluídas (SiO₂ 69% a 75%), rica em álcalis (Na₂O+K₂O ≥ 8,0%), empobrecidas em MgO (≤ 0,45%), CaO (≤ 1,42%) e TiO₂ (≤ 0,36%) e teores moderados de Fe₂O_3t (2,16 a 3,53%). Apresentam natureza transicional entre metaluminosa e peraluminosa (predomínio do último) e possuem afinidade subalcalina/monzonítica (cálcio-alcalina de alto K). Diagramas de Harker mostram correlações negativas em Fe₂O_3t, MgO e CaO, indicando fracionamento de máficos e plagioclásio. O espectro de ETR mostra enriquecimento dos ETR leves com relação aos ETR pesados (La_N/Yb_N = 23,70 a 0,23), com anomalia negativa no Eu (Eu/Eu* = 0,70 a 0,23), sugerindo fracionamento ou acumulação na fonte de feldspatos (plagioclásio). A integração dos dados permite correlacionar às rochas do PGSR àquelas referidas na literatura como Suíte Cálcio-Alcalina de Alto K Equigranular. Considerações sobre as condições de cristalização para as rochas do PGSR foram obtidas a partir da integração de dados petrográficos e litogeoquímicos, os quais indicaram atuação de condições moderadas a elevadas de ƒO₂ (paragênese mineral titanita + magnetita + quartzo), magma progenitor saturado em H₂O (cristalização precoce das biotitas), atuação de processos tardi-magmáticos de fluidos ricos em ƒCO₂, H₂O e O₂ causando alterações em parte da assembleia mineral (carbonatação e saussuritização dos plagioclásio, cloritização das biotitas e esfenitização dos opacos). Condições de termobarométricas foram estimadas com base em parâmetros geoquímicos (Zr e P₂O₅), bem como por minerais normativos CIPW, com resultados mostrando temperatura mínima de liquidus da ordem de 800°C e temperatura de solidus da ordem de 700°C. As pressões final/mínima de cristalização sugerem ser da ordem de 3 a 5 Kbar. A presença de minerais zonados (plagioclásio e allanita) associadas a dados litogeoquímicos diagramas bi-log para Rb vs Ba e Rb vs Sr sugerem a atuação da cristalização fracionada como processo dominante na evolução magmática do PGSR. Estudos geocronológicos U-Pb e isotópicos Sm-Nd indicam, respectivamente, que o biotita monzogranito possui idade de cristalização de 557±13 Ma, com idade modelo T_DM de 2,36 Ga, tendo valor de e_Nd para a idade de cristalização de -20,10, permitindo inferir fonte crustal paleoproterozoica para o magma.

A porosidade e permeabilidade em zonas fraturadas podem aumentar devido a fluidos ascendentes em sistemas cársticos. Este trabalho apresenta uma análise estrutural de duas cavernas hipogênicas da América do Sul . A área de estudo inclui a Toca da Boa Vista (TBV) e Toca da Barriguda (TBR), que possuem 115 km e 32 km respectivamente. Este sistema cárstico ocorre em carbonatos neoproterozoicos da Formação Salitre, porção norte do cráton São Francisco. Durante o Brasiliano foram formados cinturões de dobramento ao redor do cráton com padrão compressivo desenvolvido entre 740-580 Ma. A metodologia inclui mapas de condutos do Grupo Bambuí de Pesquisas Espeleológicas, a partir dos quais foram elaborados mapas estruturais das cavernas e comparação com a deformação regional. Os softwares usados para processamento de dados estruturais foram: Openstereo, Stereonet 8, Georient 9.4.5 e Tectonic FP. A Análise da deformação do sistema TBV-TBR e o contexto regional da Formação Salitre permitiu concluir que: i) os condutos se desenvolveram ao longo de eixos de anticlinais N-S e ENE para E-W; ii) o desenvolvimento do carste foi formado pela dissolução de juntas subverticais; iii) o primeiro evento de dobramento F1 corresponde a trend N-S compressional e provavelmente se desenvolveu no Brasiliano, e, o segundo evento F2 está relacionado a compressão E-W, provavelmente mais recente que o Brasiliano. Portanto, é possível confirmar que existe relação direta dos fluidos ascendentes e dissolução hipogênica com a  deformação regional.

RESUMO

A Sequência Mesodevoniana-Eocarbonífera da Bacia do Parnaíba, litoestratigraficamente definida como Grupo Canindé, foi reinterpretada empregando-se o modelo básico da estratigrafia de sequências. Para tanto, foram analisados perfis litológicos e de raios gama de poços e linhas sísmicas da região central da bacia, elaborando-se a partir daí diagramas 1D, mapas de isócoras e uma seção estratigráfica.

Como resultados deste trabalho, foram definidos dois ciclos deposicionais de segunda ordem, referidos como Sequência Deposicional 1 (SEQ1) e Sequência Deposicional 2 (SEQ2). A SEQ1, com cerca de 37 Ma, é limitada abaixo pela Discordância Eodevoniana e equivale às formações Itaim, Pimenteiras e Cabeças.

A SEQ1 se inicia com o Trato de Sistemas de Nível Baixo, constituído por conjuntos de parassequências progradacionais em que a parte basal, predominantemente pelítica, depositou-se em um contexto de prodelta sob influência de tempestades e a superior é composta por arenitos de frente deltaica, tendo como limite superior a superfície regressiva máxima. O Trato de Sistemas Transgressivo, depositado acima, é caracterizado por conjuntos de parassequências retrogradacionais, compostos predominantemente por pelitos de plataforma rasa, depositados sob ação de tempestades. A superfície transgressiva máxima, limite superior deste trato, é posicionada em um nível de folhelho cuja radiatividade no perfil de raios gama é próxima a 150 API. O Trato de Sistemas de Nível Alto apresenta conjuntos de parassequências progradacionais, compostos por pelitos e arenitos depositados em ambientes plataformal, flúvio-estuarino e periglacial, tendo como limite superior a Discordância Neodevoniana.

A SEQ2, que se segue, compreende um intervalo de cerca de 15 Ma e equivale à Formação Longá. A mesma foi depositada em ambiente plataformal, iniciando com o Trato de Sistemas de Nível Baixo, caracterizado por um conjunto de parassequências progradacional, seguido do Trato de Sistemas Transgressivo, de caráter retrogradacional. O limite superior deste trato corresponde à superfície transgressiva máxima ou ainda, a fusão desta superfície com o limite de sequência, que constitui a Discordância Eocarbonífera, onde a seção sobreposta foi erodida. Tal seção, que corresponde ao Trato de Sistemas de Nível Alto, é restrita às porções em que a erosão que originou a Discordância Eocarbonífera foi menos efetiva, preservando os registros desta unidade.

Resumo

A Sequência Neocarbonífera-Eotriássica corresponde ao terceiro grande ciclo sedimentar da Bacia do Parnaíba e concerne litoestratigraficamente ao Grupo Balsas. Esta sequência é descrita como um pacote de rochas cujos sedimentos foram depositados em um ambiente complexo, clástico/evaporítico de mar raso, gradando para um ambiente lacustre/desértico. O principal objetivo deste trabalho foi realizar uma análise estratigráfica da Sequência Neocarbonífera-Eotriássica, visando uma melhor compreensão da sua evolução. Para tal, foram empregados os conceitos modernos e genéticos da estratigrafia, utilizando-se como base de dados informações de poços e seções sísmicas. Para o intervalo estratigráfico em questão foram identificadas três sequências deposicionais. A Sequência 1 corresponde a rochas que foram depositadas inicialmente a partir de um sistema fluvial, que passa para um sistema marinho raso implantado durante uma fase transgressiva, e que posteriormente evolui para um sistema deltaico. A Sequência 2 corresponde a rochas que foram depositadas a partir de um ambiente lacustre/desértico, representando uma fase regressiva importante que culmina com a implantação de um ambiente desértico, o qual corresponde à Sequência 3. Na análise sismoestratigráfica foi possível reconhecer as superfícies cronoestratigráficas e as unidades genéticas identificadas em poços e analisar a sua expressão lateral. De modo geral, as sismofácies reconhecidas nas seções sísmicas apresentam-se com configurações paralelas a subparalelas, com grande continuidade lateral, sugerindo uma constância na taxa de sedimentação durante a deposição desta sequência.

Neste trabalho foi realizado um estudo para a obtenção de parâmetros para um modelo regional de velocidades 1D válido para a Província Borborema, NE do Brasil. Para tanto, foram utilizados eventos que ocorreram na mesma entre 2001 e 2013 com magnitude acima de 2.9 e que tiveram epicentros bem determinados por redes locais de estações ou back azimuth, quando os dados são de boa qualidade. Foram escolhidos 7 eventos ocorridos nas principais áreas sísmicas da Província Borborema. Os eventos selecionados foram, ao todo, registrados em 74 estações das redes: RSISNE, INCT-ET, Milênio, João Câmara – RN, São Rafael – RN, Caruaru - PE, São Caetano - PE, Castanhão - CE, Santana do Acarau - CE, Taipu – RN e Sobral – CE e a estação RCBR da rede IRIS/USGS - GSN. Para a determinação dos parâmetros do modelo realizou-se a inversão do tempo de percurso através de um ajuste de retas aos tempos observados. A validação deste modelo se deu de modo independente através da comparação com outros modelos conhecidos (globais e regionais para o Brasil).

O modelo final, nomeado MBB, apresenta um modelo crustal lateralmente homogêneo composto por duas camadas com crosta superior de 11,45 km de espessura e uma crosta com espessura total de 33,90 km, sendo a base da segunda camada limitada pela descontinuidade de Moho. A velocidade da onda P na crosta superior foi estimada em 6,00 Km/s e na crosta inferior 6,64 Km/s. A velocidade da onda P no manto superior foi estimada em 8,21 Km/s com uma razão VP/VS de aproximadamente 1,740 ± 0,002.

A utilização de fertilização química em perímetros agricultáveis proporciona um incremento da produtividade, embora eventualmente possa ocasionar uma depreciação qualitativa do manancial hídrico subterrâneo, sobretudo se este for de natureza não confinada. Nesse contexto, o presente trabalho apresenta resultados referentes a uma análise do grau de proteção natural do Aquífero Barreiras em uma área situada no litoral leste do Estado do Rio Grande do Norte-Brasil. O referido aquífero é de natureza clástica e possui caráter hidráulico não confinado, fato este que naturalmente lhe confere uma susceptibilidade à contaminação, proveniente de eventuais cargas contaminantes impostas na superfície do terreno. Estes contaminantes estariam associados com a lixiviação de excedentes da fertilização não assimilados pela vegetação. A metodologia utilizada foi fundamentada na utilização conjunta de dados hidrogeofísicos, particularmente de modelos inversos de sondagens elétricas verticais-SEVs e informações de perfis de poços, possibilitando a obtenção de cartografias de condutância longitudinal (S), dada em mili-Siemens (mS), e vulnerabilidade do aquífero. Essas cartografias foram elaboradas com ênfase para a zona não saturada sobrejacente, ressaltando sobretudo sua espessura e ocorrência de litologias argilosas. Dessa forma, o mapa de condutância longitudinal e vulnerabilidade revelaram áreas mais susceptíveis à contaminação nos setores nordeste e centro-leste da área de estudo, com valores iguais ou inferiores a 10mS e maiores ou iguais a 0.50, respectivamente. Por outro lado, o setor sudoeste mostrou-se menos susceptível à contaminações, com valores de condutância longitudinal e índices de vulnerabilidade maiores ou iguais a 35mS e menores ou iguais a 0.40, respectivamente.

Os estuários tem grande importância como abrigo e berçário natural de animais marinhos, provêm peixes para o homem,sustenta a cadeia alimentar, controla as ações erosivas e alagamentos, atua nosistema de filtragem natural da poluição e purificação do ar. O Rio Potengi temsido afetado por diversos fatores antrópicos ao longo dos anos, com váriosdesastres ambientais que mataram peixes, aves e outros animais. Para analisar asituação recente do estuário do Rio Potengi, foram coletadas 42 amostras, 18 emOutubro/2011 ao longo do Rio Potengi e sua foz, e 24 em Janeiro/2012, incluímosa plataforma interna. Análises univariadas (índices ecológicos) e multivariadas(PCA, MDS, CLUSTER e BIOENV) foramaplicadas à matriz dos dados biológicos de foraminíferos e abióticos (CaCO3,salinidade, profundidade, temperatura e granulometria). 

Os resultados mostram a dominância deforaminíferos oportunistas A. tepida,B. striatula, Q. patagonica e Q. milettiespecialmente nas regiões próximas às fazendas de carcinicultura e ao esgoto doCanal do Baldo em ambientes de granulometria fina, e Q. lamarckiana indicadora da penetração da cunha salina e ambientesde alta hidrodinâmica associada a sedimentos de areia grossa a muito fina. A presença de espécies característicasmarinhas H. boueana, E. discoidale, P. atlanticum, T. earlandie T. gramen na Foz do Rio Potengi ena plataforma interna indicam ambientes de altas salinidades. A ocorrência dealgumas espécies tolerantes à baixa salinidade como T. inflata e T. squamatano Canal do Rio Potengi sugerem que provavelmente devem ter sido transportadosdo manguezal próximo à foz do Rio Potengi para as regiões de plataformainterna, sugerindo que o contribuinte fluvial é capaz de exportar organismos deágua doce preferivelmente em direção sul do que em direção norte. 

A região noroeste do estado do Ceará é uma das principais regiões com sismicidade ativa dentro da Província Borborema. Há relatos de um abalo sísmico ocorrido em 1810, na cidade de Granja. A partir de janeiro de 2008, a atividade sísmica na região aumentou consideravelmente e foi instalada uma rede sismográfica com 11 estações digitais na serra da Meruoca. Em 2009, outra sequência de abalos sísmicos iniciou-se e outra rede foi instalada na cidade de Santana do Acaraú, com até 6 estações digitais. Os resultados mostrados nessa tese foram obtidos através da análise dos dados registrados nessas duas redes, principalmente.

As áreas epicentrais estão localizadas nas proximidades da parte nordeste do Lineamento Transbrasiliano, uma zona de cisalhamento com trend NE-SW que corta a região de estudo. Identificamos zonas sísmicas com hipocentros localizados entre 1km e 8km. Os mecanismos focais encontrados foram do tipo transcorrente, predominante na Província Borborema.

Foi realizada uma integração entre dados sismológicos, geológicos e geofísicos (aeromagnéticos) e mostramos que as falhas sismogênicas encontradas estão orientadas na mesma direção das estruturas frágeis locais observadas em campo e de lineamentos magnéticos.

A direção do  SHmax (esforço máximo) na região foi estimada usando uma inversão de sete mecanismos focais espalhados pela região e usamos as direções dos falhamentos sismogênicos. O esforço horizontal possui máxima compressão (σ₁=300°) com orientação NW – SE e extensão (σ₃=210°) com direção NE – SW e σ₂ vertical. Esses resultados estão de acordo com resultados de estudos anteriores, mas foi usado um número maior de mecanismos focais.

A atividade sísmica registrada na área de estudo não está relacionada com uma possível reativação do Lineamento Transbrasiliano, até o momento.

Nesta tese são apresentados e discutidos os resultados de correlação do ruído sísmico em dois contextos: região intraplaca e Dorsal Meso-oceânica. O método de interferometria de cauda de onda (coda wave interferometry—CWI) também foi utilizado para os dados da região intraplaca. A correlação do ruído permite recuperar a função de Green empírica entre dois receptores , como se uma das estações atuasse como uma fonte (virtual). Esta técnica éamplamente utilizado em sismologia para a imagem do subsolo e para monitorar mudanças estruturais associadas principalmente com erupções vulcânicas e terremotos grandes (mb > 6.0). No estudo da região intraplaca, fomos capazes de detectar mudanças estruturais localizadas relacionadas com esta pequena sequência de terremotos, cujo evento principal é de mR 3.7, no Nordeste do Brasil. Nós também mostramos que a normalização de 1-bit de e o branqueamento spectral provoca perdas de detalhes na forma de onda e que a auto- correlação de fase, que é pouco sensível à amplitude , parece ser mais sensível e robusta para a nossa análise. A análise de 6 meses de dados usando correlações cruzadas detecta claramente alterações do meio logo após do evento principal, enquanto que as auto- correlações essencialmente detectam alterações após 1 mês. Estas mudanças na correlação cruzada e na auto-correlação podem serexplicadas pela redistribuição da pressão do fluido ocasionadas mudanças hidromecânicas e novos caminhos preferenciais para difusão de pressão e fuidos , devido a terramotos que ocorrem mais tarde. No estudo da Dorsal Meso-oceânica, investigamos as mudanças estruturais associadas a um terremoto de mb 4,9 aolongo da falha transformante de São Paulo. Os dados foram registrados por a única estação sísmica localizada a menos de 200 km da Dorsal Meso-oceânica. Os resultados da auto-correlação de fase por um período de 5 meses, mostram uma forte mudança de meio co-sísmica seguido por uma recuperação pós-sísmica relativamente rápida. Esta mudança do meio provavelmente está relacionada aos danos causados pelo terremoto de mb 4.9. O processo de cicatrização (enchimento das novas fissuras) que durou 60 dias pode ser decomposto em duas fases, uma recuperação rápida na fase pós-sísmica (de 70% em ~ 30 dias) precoce e uma recuperação relativamente lenta depois (de 30% em ~ 30 dias) No estudo de interferometria de cauda de onda, monitoramos mudanças temporais da subsuperfície causada pela sequência de pequenos terremotos intraplaca mencionado anteriormente. O método foi validado com dados sintéticos. Fomos capazes de detectar uma mudança da fonte de 2.5% e uma redução de 15% da quantidade dos espalhadores. A partir dos dados reais, observamos uma rápida diminuição da correlação da cauda da onda após do evento sísmico mR 3.7. Isso indica uma mudança rápida do subsolo na região da falha induzida pelo terremoto.

Ambientes profundos do nordeste brasileiro carecem de dados e conhecimento e representam um ambiente de importância econômica e ambiental. Esta dissertação apresenta os resultados do primeiro imageamento realizado no talude continental, em área adjacente a Bacia Potiguar, na margem equatorial brasileira (NE Brasil). Dados de batimetria multifeixe forneceu uma cobertura completa do fundo oceânico entre o talude superior e o talude intermediário (100-1300 m). Quinze canyons submarinos foram mapeados. A forma do talude reflete na distinta distribuição espacial dos canyons. A parte oeste apresenta perfis convexos o que implicou numa maior quantidade de incisões pelos canyons. Alguns deles possuem paredes com declividades maiores que 35°. Os canyons foram agrupados de acordo com a sua localização (A, B, C, D e E) e classificados de acordo com sua morfologia. As características dos canyons A4 e D1 (Tipo 1) como cabeceiras são entalhadas na plataforma, conexão com sistemas fluviais, altas sinuosidades, formas em ‘V’, terraços ao longo das margens, feições erosivas como deslizamento de massa e ravinas permitem deduzir uma sedimentação areno-cascalhosa. Estes canyons são associados à deposição de sistemas de leques submarinos que têm sido considerados reservatórios de hidrocarbonetos permeáveis. A presença de ravinas, ranhuras e dunas demonstram o papel das correntes de fundo na forma do talude. Os alargamentos dos canyons B2 e B4 e a mudança na direção do curso do canyon D1 onde eles cruzam a falha de borda da bacia implicam que a tectônica também influencia na morfologia dos ambientes profundos da bacia potiguar. A cobertura sedimentar apresenta uma diminuição da granulometria à medida que a profundidade aumenta e é representada por quatro fácies sedimentares: silte, silte arenoso, areia siltosa e areia com cascalho. O teor de carbonato de cálcio é considerado moderado a alto e o de matéria orgânica é baixo. O talude continental é considerado misto, pois os sedimentos possuem componentes siliciclásticos e bioclásticos. Dentre os siliciclásticos destacam-se calcita, dolomita, quartzo e os argilominerais. A presença de alguns minerais pesados tais como zircão, turmalina e rutilo, bem como bioclásticos fragmentados, indicam a maturidade dos sedimentos e a contribuição dos Rios Açu e Apodi para os sedimentos da área de estudo. A morfologia, classificação dos canyons e sedimentologia podem fornecer informações sobre possibilidade de prospecção petrolífera e gestão ambiental.

A área estudada situa-se, geograficamente, no extremo NE do Estado do Rio Grande do Norte situados nos municípios de Taipu e Poço Branco e geologicamente inseridos no Terreno Cristalino São José do Campestre pertencente à Província Borborema, onde observando relações de campo, dados petrográficos e geoquímicos, permitiram individualizar três plútons denominados: Gameleira, Taipu e Pitombeira.

O Plúton Gameleira é composto por rochas granodioríticas caracterizadas por fenocristais zonados de plagioclásios e tendo anfibólio e biotita como máficos principais. Quimicamente, são rochas metaluminosas, de natureza cálcio-alcalina e apresentam caráter magnesiana. O Plúton Pitombeira é composto por duas fácies: (a) uma monzogranítico à sienogranítica de textura grossa a porfirítica caracterizada por fenocristais de K-feldspato e (b) uma de composição quartzo diorítica a tonalítica distinta por suas ripas de plagioclásio parcialmente zonadas e com borda de resfriamento. Quimicamente são rochas transicionais entre metaluminosas a peraluminosas, de natureza subalcalina (cálcio-alcalina de alto K) e caráter ferroso. Por fim, o Plúton Taipu é formado por rochas monzograníticas a sienograníticas, contendo biotita como máfico principal. São rochas peraluminosas, de natureza subalcalinas (cálcio-alcalina de alto K) e caráter ferroso.

No que se refere às análises de elementos terras raras (ETR), pode-se inferir que os três plútons estudados apresentam anomalias negativas de Eu e enriquecimento em ETR leves, com razões de La_N/Yb_N entre 9,38 a 16,20 ppm (Plúton Gameleira), 17,99 a 31,39 ppm (fácies granítica do Plúton Pitombeira), 14,15 a 21,81 ppm (fácies diorítica do Plúton Pitombeira) e 15,17 a 175,41 ppm (Plúton Taipu). Analisando os dados químicos e os diagramas em conjunto é possível sugerir que os plútons estudados pertencem a um ambiente tectônico tardi a pós-colisional.

Abstract

The studied area is geographically situated in the extreme northeastern of Rio Grande do Norte State located in the municipalities of Taipu and Poço Branco and geologically entered in the Crystalline Land São José do Campestre which belongs to Borborema Province, where by observing the field relations, petrographic and geochemical datas, has allowed to individualize three plutons named: Gameleira, Taipu and Pitombeira.

The Gameleira Pluton consists in granodioritic rocks characterized by phenocrysts zoned plagioclase having amphibole and biotite as the main mafic. Which are Chemically, metaluminous rocks, naturally from calc-alkaline and present magnesian character. The Pitombeira Pluton consists in two facies: (a) one monzogranite-syenogranite to coarse texture and to the porphyritic characterized by K-feldspar phenocrysts and (b) quartz dioric-tonalitic composition to a distinct for its laths of plagioclase partially zoned and also with cooling edges. Chemically are transitional rocks between metaluminous to peraluminous, naturally from subalkaline (high-K calc-alkaline) and ferrous character. Thus, the Taipu pluton is formed by monzagranitic-sienogranitic rocks, containing biotite as its main mafic. They are peraluminous rocks, naturally subalkaline (high-K calc-alkaline) and ferrous character.

As regards to the rare earth elements analysis (REE), which can be inferred that the three studied plutons exhibit negative anomalies of Eu and REE slight enrichment, with ratios of LaN / YbN between 9.38 to 16.20 ppm (Gameleira Pluton) 17.99 to 31.39 ppm (Pluton Pitombeira granitic facies), from 14.15 to 21.81 ppm (Pluton Pitombeira dioritic facies) and from 15.17 to 175.41 ppm (Pluton Taipu). Analyzing the chemical and diagrams datas to one another, it’s allowed to suggest that the studied plutons belong to a late tectonic environment to a post-collisional.

A zona de transição do manto está definida por duas descontinuidades sísmicas, nominalmente a 410 e 660 km de profundidade, que resultam de transformações de fase no mineral olivina. A topografia dessas descontinuidades fornece informações sobre as variações laterais de temperatura da zona de transição. Neste trabalho, foram utilizadas conversões P-para-S telessísmicas registradas em 32 estações sísmicas de banda larga na Província Borborema para determinar a espessura da zona de transição abaixo desta região e para investigar se há mudanças laterais da temperatura neste intervalo de profundidade, para isso foi feito o empilhamento e a migração de funções do receptor. Na Província Borborema, estudos geofísicos revelaram a existência de uma anomalia de geóide que poderia refletir a presença de uma anomalia térmica, a qual estaria relacionada à origem do vulcanismo intraplaca e da epirogênese que atingiram a Província no Cenozóico. Vários modelos têm sido propostos para explicar esses eventos, dentre eles o modelo de pluma do manto e de eventos rasos como células de convecção de pequena escala. Os resultados deste trabalho mostram que essa anomalia térmica não atinge a profundidade da zona de transição do manto, visto que não foram identificadas variações significativas na espessura da zona de transição. Contudo foram observadas regiões de topografia baixa para ambas as descontinuidades (410 e 660 km) que aproximadamente se sobrepõem no espaço, sugerindo que variações laterais negativa nas velocidades acima de 410 km de profundidade podem existir abaixo da Província Borborema. O que é consistente com a estrutura de baixa densidade que seria consequência de uma alteração térmica. Portanto a fonte magmática que teria provocado no Cenozóico o vulcanismo intraplaca e estaria relacionada ao soerguimento na Província, estaria confinada acima da zona de transição.

RESUMO

Este estudo foi desenvolvido em uma área localizada na plataforma externa da Bacia Potiguar, margem equatorial brasileira. A amostragem de sedimentos foi realizada em três campanhas, em torno de um poço exploratório, para comparar as propriedades dos sedimentos do fundo marinho, incluindo granulometria, composição, conteúdo de carbonato e matéria orgânica, anterior a perfuração do poço, com amostras coletadas 3 e 12 meses após a perfuração. O planejamento amostral utilizou 16 estações localizadas em 4 radiais distantes 50 m, 100 m, 250 m e 500 m do poço. Os sedimentos foram analisados nas camadas 0-2 cm e 0-10 cm. Os resultados mostraram que a cobertura sedimentar em torno do poço era pobre a muito pobremente selecionada, com granulometria predominante na fração areia grossa com granulo e cascalho, seguida por cascalho e lama. O conteúdo de carbonato de cálcio foi maior que 96%, associado a sedimentos biocláticos, e o conteúdo de matéria orgânica foi menor que 12%. Apenas pequenas variações sedimentológicas ocorreram na área afetada pelas operações de perfuração.  A principal diferença foi observada em amostras da segunda campanha, em termos de uma mudança na distribuição granulométrica associada a um aumento no conteúdo de sedimentos siliciclásticos. Este impacto ocorreu nos sedimentos mais superficias (0-2 cm), no raio mais próximo ao poço (50 m), e poderia sugerir o efeito da perfuração. Entretanto, os sedimentos coletados na campanha 3, um ano após a perfuração, voltaram a apresentar as mesmas características da primeira campanha. Estes resultados indicam que não houve variações sedimentológicas significantes devido a atividade de perfuração, e que a dinâmica oceânica na área de estudo foi forte o suficiente para recuperar as características originais do ambiente.

ABSTRACT

This study was developed in an area located on the outer shelf in the Potiguar Basin, Brazilian equatorial margin; this tropical shelf represents a modern, highly dynamic mixed carbonate-siliciclastic system. Field sampling was carried out during 3 cruises surrounding a shallow-water exploratory well to compare sediment properties of the seafloor, including grain-size, texture, mineral composition, carbonate content, and organic matter,  prior to drilling with samples obtained 3  and 12 months after drilling. The sample grid used had 16 stations located along 4 radials from 50 m the well up to a distance of 500 m. Sediments were analyzed in the first 0-2 cm, and 0-10 cm layers. The results show that sedimentary cover around the well is poor to very poorly sorted, with the particle size predominantly in the medium to coarse sand fraction, followed by gravel and mud. The content of calcium carbonate is greater than 96%, associated to bioclastic sediments, and the content of organic matter is less than 12%.  Only minor sedimentological variations occured ­in the area affected by drilling operations. The most noticeable effects were observed during the second cruise, in terms of a  change in grain size distribution associated to an increase in siliciclastic content, This impact occurred in the most surficial sediment (0-2 cm), in the radial closest to the well (50  m),  and could suggest the effects of drilling. However, in the third cruise, one year after drilling, the sediments return to show the same characteristics as in the first cruise. These results show no significant sedimentological variations due to drilling activity, and indicate that ocean dynamics in this area was high enough to recover the environment original characteristics.