Imageamento e modelagem digital com GPR em microbialitos da Fazenda Arrecife, Chapada Diamantina (BA), NE do Brasil

• Ano de defesa: 2017
• Autor(a) principal: Lima, Rebeca Seabra de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Brasil; UFRN; PROGRAMA DE PÓS-GRADUAÇÃO EM GEODINÂMICA E GEOFÍSICA
• Palavras-chave em Português: Imageamento digital; GPR; Microbialitos; CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOFISICA
• Link de acesso: https://repositorio.ufrn.br/jspui/handle/123456789/24847

This thesis involves the digital imaging and modeling of a neoproterozoic microbialitic colony in the Fazenda Arrecife (BA) outcrop, using the Ground Penetrating Radar (GPR) method and the application of mathematical attributes. Concomitantly, columnar sections and radioactive profiles acquisition were carried out, allowing the characterization of the sedimentary facies. Petrographic studies and chemical analysis (SEM/EDS and XRF) were used to identify the composition of the stylolithic levels that generate reflections in the GPR sections. The "Instantaneous 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, this attribute provided a better 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 compared to the "Energy" attribute. The attribute "Hilbert Trace/Similarity" highlighted the internal structure of the microbial community. The described facies were designated as microbialitic facies (MCme, MCm and MCma) and tempestite facies (Cahm). Minerals, such as limonite and/or siderite, were identified by the petrographic study, 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 generated 3D solid properly represents a microbial community. The attribute application to GPR data allowed to highlight the microbialitic features not observed in the original data. Therefore, this application can be used in similar geologic contexts.