Programa de Pós-Graduação em Geodinâmica e Geofísica
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Doctoral Thesis Influência de descontinuidades estruturais e sedimentares na porosidade cárstica da Formação Jandaíra, Bacia Potiguar(Universidade Federal do Rio Grande do Norte, 2022-09-08) Araújo, Renata Emily Brito de; Bezerra, Francisco Hilario Rego; Bruna, Vincenzo La; https://orcid.org/0000-0002-3512-5212; http://lattes.cnpq.br/6050302316049061; https://orcid.org/0000-0001-9362-1153; http://lattes.cnpq.br/2478904185223241; Lima Filho, Francisco Pinheiro; https://orcid.org/0000-0001-5657-5207; http://lattes.cnpq.br/9888320802954176; Vieira, Marcela Marques; Bagni, Fábio Luiz; Barbosa, Paola FerreiraEpigenic karst in carbonate rocks commonly results in progressive dissolution by the action of meteoric waters over time. The generation of secondary porosity and permeability allows for the dissolution of carbonates in geofluid reservoirs. These two factors can impact reservoir storage capacity and fluid flow. The present study investigates (1) the control of structural discontinuities (tectonic stylolites and fractures) and sedimentary discontinuities (stylolites generated by diagenesis, cross-bedding, and plane-parallel) in the generation of karst dissolution cavities, from microscale (102 - 1010µm) to mesoscale (0.1 - 5 m), and (2) the relationship of porosities formed by diagenetic processes and their impact on the generation of epigenic karst from the Jandaíra Formation, Potiguar Basin, Brazil. The study is based on micro to mesoscale analysis based on field analysis based on drone images, stratigraphic logs, structural and rock strength data collected by Schmidt's hammer. Laboratory studies focused on microtomographic images, petrography and petrophysics. . The results show that the stratabound and non-stratabound bed-perpendicular stylolites can be enlarged due to the percolation of meteoric waters until they merge and form a single channel system that cuts all the layers. The bed-parallel stylolites are at the limits of the layers and, therefore, can act as horizontal fluid conduits when well dissolved and forming channel porosity. Dissolution can occur in all diagenetic stages the carbonate rock matrix. Telodiagenesis, is the most important due to the most recent aerial exposure. The dissolution in telodiagenesis generated different types of porosity due to the dissolution of various diagenetic features previously formed, such as cementation, dolomitization, and compaction. Dissolution is also localized to preexisting discontinuities such as stylolites, fractures, and bedding surfaces. In epigenic karst systems, high percentages of microporosity are commonly due to mold, intragrain/intrafossil, and intercrystal porosities. Such porosities can be connected to microscale fractures, veins, and stylolites, further increasing the porosity and overall permeability of the rock.Master Thesis O papel das falhas na evolução de bandas de deformação na bacia do Rio do Peixe(2018-02-26) Araújo, Renata Emily Brito de; Bezerra, Francisco Hilario Rego; ; ; Mello, Cláudio Limeira; ; Medeiros, Walter Eugênio de;The fragile reactivation of continental scale pre-cambrian ductile shear zones and the development of rifte basins in northeastern Brazil occurred in the Cretaceous. 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. Shuttle radar topography, aeromagnetic, and gravity data were used to unravel the rift structure and identify master fault segments. In addition, an unmanned aerial vehicle (UAV) were used and a field study to map deformation bands close to the main rift faults. The results indicated that the Rio do Peixe Basin was formed along the reactivation of the Malta fault and the Portalegre fault.. 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 unified bands, called clusters, as far as 5 km from Portalegre Fault master faults, as far as 2.5km from Malta Fault and they are widespread in a structural high bounded by two relay ramps. The deformation bands follow the strike or are oblique to the master rift faults and become slip surfaces when a zone of deformation bands causes a zone of weakness that forms faults. The slip surfaces kinematics are consistent with those of extensional rift faults. In addition, a decrease in deformation band frequency occurs away from the master faults. 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.