Produção Nacional
Sedimentology of the Psammo-pelitic-carbonate Unit, Paranoá Group, and Sete Lagoas Formation, Bambuí Group: examples of mixed carbonate-siliciclastic sedimentation in the Proterozoic of the Brasília Fold Belt
2012; Sociedade Brasileira de Geologia; Volume: 42; Issue: 3 Linguagem: Inglês
10.5327/z0375-75362012000300006
ISSN2177-4382
AutoresJosé Elói Guimarães Campos, Jéssica Bogossian, Rômulo Mendes Carvalho,
Tópico(s)Geological and Geophysical Studies
ResumoThe mixed carbonate-siliciclastic platforms are still poorly studied, although they represent important regional sedimentary successions in the Brasília Fold Belt. The aim of the present paper was to determine the deposition conditions of the Psammo-pelitic-carbonate Unit (top of the Paranoá Group) and the Sete Lagoas Formation (base of the Bambuí Group) in the Brasília Fold Belt, central Brazil. The sedimentation of the two sequences occurred in a mixed platform controlled by the bottom paleogeography where carbonate facies were deposited in shallow environment and detrital facies in deeper water. In the Paranoá Group, small limestone and dolomite lenses are found in the highest areas, whereas pelites were deposited in depressions and psammites inplatform channels. In the Sete Lagoas Formation, the major carbonate lenses were deposited over the highs derived from the post-glacial erosion surface that marks the unconformity between the Paranoá and Bambuí groups. In both units, micritic mud predominates, and reworking by waves occurred sporadically and associated with progradation-retrogradation. The aggradation of terrigenous material caused deposition of pelitic facies. The dimensions, thickness, and distribution of carbonate lenses show that the paleorelief was more pronounced during the deposition of the Sete Lagoas Formation, when compared with the Psammo-Pelitic-Carbonate Unit. On the other hand, the sedimentation rate of Psammo-Pelitic-Carbonate Unit was greater than the one of the Sete Lagoas Formation.
Referência(s)