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Aspetos microfaciológicos da formação da Leba, Proterozoico (Sudoeste de Angola)
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Abstract(s)
RESUMO: A Formação da Leba é uma unidade carbonatada de referência do Proterozoico do Cratão do Congo, Sudoeste de Angola, composta por dolomitos silicificados com laminitos microbianos e estromatólitos. Este trabalho preliminar descreve as principais microfácies que caracterizam esta unidade, baseada no estudo de várias secções do Planalto da Humpata. Os resultados confirmam o domínio da dolomite em toda a sucessão, localmente fortemente silicificada. As fácies são bastante diferenciadas, compreendendo bioconstruções microbianas, incluindo micro domos estromatolíticos, e uma grande variabilidade de outras texturas, desde dolomicritos/mudstones a grainstones intraclásticos e extraclásticos. Tendo em conta que a dolomite é de origem primária, são identificados vários processos diagenéticos, incluindo dolomitização e diferentes fases de silicificação.
ABSTRACT: The Leba Formation is a reference carbonate unit from the Proterozoic of the Congo Craton, Southwest Angola, composed of cherty dolostones with microbial laminites and stromatolites. This preliminary work describes the microfacies that characterize this unit, based on the study of several sections of the Humpata Plateau. The results confirm the dominance of dolomite in the whole succession, locally strongly silicified. Facies are markedly differentiated, comprising microbial constructions, including micro domal stromatolites, and a wide variability of other textures, ranging from dolomicrites/mudstones to intraclastic and extraclastic grainstones. Considering that dolomite of primary origin is present, several diagenetic processes are identified, including dolomitization and different phases of silicification.
ABSTRACT: The Leba Formation is a reference carbonate unit from the Proterozoic of the Congo Craton, Southwest Angola, composed of cherty dolostones with microbial laminites and stromatolites. This preliminary work describes the microfacies that characterize this unit, based on the study of several sections of the Humpata Plateau. The results confirm the dominance of dolomite in the whole succession, locally strongly silicified. Facies are markedly differentiated, comprising microbial constructions, including micro domal stromatolites, and a wide variability of other textures, ranging from dolomicrites/mudstones to intraclastic and extraclastic grainstones. Considering that dolomite of primary origin is present, several diagenetic processes are identified, including dolomitization and different phases of silicification.
Description
Keywords
Dolomitos Estromatólitos Microfácies Proterozoico Angola Dolostones Stromatolites Microfacies Proterozoic
Citation
Duarte, L., Barata, J. & Oliveira, C. L. (2025). Aspetos microfaciológicos da formação da Leba, Proterozoico (Sudoeste de Angola). In: Comunicações Geológicas, 2025, vol. 112, Fascículo Especial I, pp. 77-80. https://doi.org/10.34637/vehs-7763
Publisher
LNEG - Laboratório Nacional de Energia e Geologia