Faciologic characterization and sedimentary evolution of Moeda Formation (Minas Supergroup) in Northwestern Quadril?tero Ferr?fero, Minas Gerais.

A Forma??o Moeda, ao longo da regi?o noroeste do Quadril?tero Ferr?fero, registra os primeiros est?gios da Bacia Minas, desenvolvida no limite Neoarqueano/Paleoproterozoico no sul do Cr?ton do S?o Francisco (CSF). Este trabalho analisa essa unidade a partir de seis perfis estratigr?ficos de detalhe nos quais foram identificadas nove f?cies sedimentares: quatro conglomer?ticas (Gms, Gm, Gt e Gp), tr?s essencialmente aren?ticas (St, Sp e Sh) e duas predominantemente pel?ticas (Fl e Fsc). As se??es estratigr?ficas foram correlacionadas, possibilitando o agrupamento das f?cies em cinco associa??es geneticamente relacionadas. As associa??es de f?cies AF1 e AF2 representam sistemas de leques aluviais que evolu?ram para plan?cies fluviais entrela?adas. AF3 est? relacionada a um sistema lacustre associado a marinho raso nas por??es distais. Por fim, as associa??es de f?cies AF4 e AF5 representam plan?cies fluviais entrela?adas encerradas por uma transgress?o marinha no est?gio final de evolu??o da bacia. Com o aux?lio do mapeamento geol?gico-estrutural de detalhe dessas associa??es e da confec??o de uma se??o restaurada foi poss?vel interpretar que as AF1, AF2, AF3 e a por??o basal da AF4 foram depositadas durante os est?gios iniciais do rifteamento continental, e as demais associa??es materializam a transi??o rifte-margem passiva.The Moeda Formation, along the northwestern region of the Quadril?tero Ferr?fero, registers the first stages of the Minas basin, during the Neoarchean/Paleoproterozoic, south of the S?o Francisco Craton. This paper examines this unit from six stratigraphic sections where nine sedimentary facies were characterized: four conglomerate facies (Gms, Gm, Gt and Gp), three sandstones (St, Sp and Sh) and two predominant mudstones (Fl and Fsc). The stratigraphic sections were correlated allowing the grouping of the facies in five genetically related associations. The associations of facies AF1 and AF2 presents an alluvial fan system which evolved into interlaced fluvial plains. AF3 is related to a shallow marine associated lake system in the distal portions. Finally, the association of facies AF4 and AF5 represent interlaced fluvial plains enclosed by a marine transgression in the final evolution stage of the basin. Based on the geological-structural detail mapping of these facies associations and in a restored section, it is interpreted that AF1, AF2, AF3, and the basal portion of AF4 were deposited during the initial stages of the continental rift, and the other associations materialize the transition between the stages rift and passive margin