Made available in DSpace on 2015-03-13T17:08:32Z (GMT). No. of bitstreams: 1 ThalesESJ_DISSERT.pdf: 669387 bytes, checksum: 33a20d208304804215535ed96770330f (MD5) Previous issue date: 2012-04-27 / In this study, the methodological procedures involved in digital imaging of collapsed paleocaves in tufa using GPR are presented. These carbonate deposits occur in the Quixer? region, Cear? State (NE Brazil), on the western border of the Potiguar Basin. Collapsed paleocaves are exposed along a state road, which were selected to this study. We chose a portion of the called Quixer? outcrop for making a photomosaic and caring out a GPR test section to compare and parameterize the karst geometries on the geophysical line. The results were satisfactory and led to the adoption of criteria for the interpretation of others GPR sections acquired in the region of the Quixer? outcrop. Two grids of GPR lines were acquired; the first one was wider and more spaced and guided the location of the second grid, denser and located in the southern part of the outcrop. The radargrams of the second grid reveal satisfactorily the collapsed paleocaves geometries. For each grid has been developed a digital solid model of the Quixer? outcrop. The first model allows the recognition of the general distribution and location of collapsed paleocaves in tufa deposits, while the second more detailed digital model provides not only the 3D individualization of the major paleocaves, but also the estimation of their respective volumes. The digital solid models are presented here as a new frontier in the study of analog outcrops to reservoirs (for groundwater and hydrocarbon), in which the volumetric parameterization and characterization of geological bodies become essential for composing the databases, which together with petrophysical properties information, are used in more realistic computer simulations for sedimentary reservoirs. / Nesse trabalho s?o apresentados os procedimentos metodol?gicos envolvidos no imageamento digital de paleocavernas colapsadas em tufas carbon?ticas que ocorrem na borda oeste da Bacia Potiguar com GPR. Foi mapeada uma ?rea em Quixer? (CE) e selecionado um afloramento em um corte de estrada, denominado de Afloramento Quixer?. Foi escolhida uma por??o deste afloramento para confec??o de um fotomosaico e levantamento de uma se??o-teste com o GPR para a compara??o e parametriza??o das geometrias c?rsticas aflorantes e imageadas na linha geof?sica. Os resultados foram satisfat?rios e permitiram a ado??o de crit?rios para a interpreta??o das paleocavernas colapsadas em outras se??es GPR, levantadas na regi?o do afloramento. Foram adquiridas duas malhas de linhas GPR, a primeira mais ampla e espa?ada norteou a loca??o da segunda, mais adensada, na por??o sul do Afloramento Quixer?. Nos radargramas foram interpretadas e parametrizadas as geometrias das principais paleocavernas colapsadas. Para cada malha foi elaborado um modelo de s?lido digital do Afloramento Quixer?, sendo que o primeiro modelo permitiu o reconhecimento da distribui??o geral das tufas e a localiza??o das paleocavernas colapsadas, enquanto o segundo modelo digital, por ser mais detalhado, possibilitou n?o apenas a individualiza??o 3D das principais paleocavernas, mas tamb?m o c?lculo dos seus respectivos volumes. Os modelos de s?lidos digitais s?o aqui apresentados como uma nova fronteira no estudo de afloramentos an?logos a reservat?rios (h?dricos ou petrol?feros), na qual a parametriza??o e a caracteriza??o volum?trica dos corpos geol?gicos passam a ser fundamental para compor bancos de dados, que conjuntamente com informa??es de propriedades petrof?sicas s?o utilizados em simula??es computacionais mais real?sticas de reservat?rios.

The Lower Ordovician El Paso Group is a >400-m-thick carbonate succession exposed in the Franklin Mountains, El Paso, Texas. The El Paso Group contains multiple breccias related to collapsed-paleocave systems. These breccias have been documented as having formed during the top-Lower Ordovician Sauk depositional supersequence lowstand. Evidence presented in this study suggests that cave formation may have been as much as 350 million years younger and related to Laramide oblique right lateral compression. Regardless of the timing of formation, the breccias mapped in this study are of collapsed paleocave origin based on breccia clast organization and matrix content. Speleogenetic models are compared against observations of breccia distribution by direct field observations and mapping on sub-meter airborne light detection and ranging or lidar data. Point vectors were defined for every point within study area to highlight subtle changes in outcrop erosional profile for mapping geological features directly on the lidar point cloud. In addition, spectral data from airborne photography and hyperspectral image analysis were used assist in geological contact definition. A digital outcrop model was constructed from 3D geologic mapping results from which spatial statistic were extracted and used to reconstruct collapsed paleocave breccia bodies. The resultant breccia geometries were compared against laser-scanned modern cave dimensions, from Devil's Sinkhole, Rocksprings, Texas, and used in analysis of conceptual models for cave formation. The breccias of the southern Franklin Mountains follow linear trends that closely match Riedel shear fracture patterns predicted from right-lateral oblique compression. Stress orientations that match right-lateral oblique compression in the Phanerozoic of the El Paso region are related to the Laramide orogeny. The relationship of observed structures and the orientation of collapse breccias may indicate that southern Franklin Mountain breccia bodies are the result of a solution-enhanced tectonic karst system. / text