Produção Nacional
ESTRATIGRAFIA E EVOLUÇÃO PALEOGEOGRÁFICA DO GRUPO SANTA BÁRBARA (EDIACARANO) NA SUB-BACIA CAMAQUÃ OCIDENTAL, RIO GRANDE DO SUL, BRASIL
2006; Sociedade Brasileira de Geologia; Volume: 36; Issue: 3 Linguagem: Inglês
10.25249/0375-7536.2006363550565
ISSN2177-4382
AutoresGélson Luís Fambrini, Renato Paes de Almeida, Antônio Romalino Santos Fragoso-Cesar,
Tópico(s)Geochemistry and Geologic Mapping
ResumoIn the south and southeastern Brazil and in the south of Uruguay post-Brasiliano Cycle sedimentary and volcanogenic deposits of the Ediacaran-Early Paleozoic occur. In the state of Rio Grande do Sul the best exposures of these rock covers crop out and were related to the Camaquã Supergroup. The supergroup, with a thickness of over 8,000m, is formed by the following units, from base to top: (i) siliciclastic Maricá Group; (ii) volcano-sedimentary Bom Jardim Group; (iii) volcanic Acampamento Velho Formation; (iv) siliciclastic Santa Bárbara Group; (v) siliciclastic Guaritas Group; and (vi) Rodeio Velho intrusive suite. The Santa Bárbara Group occur in three sub-basins NNE-SSW oriented, named Western, Central and Eastern Camaquã respectively and separated by the Caçapava do Sul and Serra das Encantadas basement highs. This work aims to play a paleogeographic evolution of the Western Camaquã Sub-Basin. The sedimentary units of the Western Camaquã Sub-Basin comprise, at the base, conglomerates and sandstones with subordinate siltstones and fine-grained sandstones of the Estância Santa Fé Formation. These deposits are interpreted to be alluvial fans dominated by sheet-floods processes, and channel deposits in braided rivers. Above these rhythmites in the arroio Seival and arroio Santa Bárbara valleys occur, composing a progradational succession to shallow water tabular sandstones, with evidence of tide action, named Seival Formation. This unit is covered by braided rivers sandstones and subordinate conglomerates of the Serra dos Lanceiros Formation. The fluvial succession is interrupted by succession of lagoonal rhythmites and fine-sandstones with evidence of tide action comprising the Arroio Umbu Formation. Lagoonal siltstones and sandstones were overlaid by delta-front fine-to-medium sandstones representing the progradation of estuarine delta. Over the lagoonal deposits new progradation of fluvial sandstones followed by alluvial fans conglomerates occur, comprising the Pedra do Segredo Formation. Important event of reorganization is registered in the Pedra do Segredo Formation through the uplift of the Caçapava do Sul High. The contribution of detritus by the basement high of the Caçapava do Sul and the presence of alluvial fans suggest that tectonic isolation of the Western Camaquã Sub-Basin occurred only at late stages of evolution of the group, by the progradation of alluvial facies over the lagoonal and estuarine environments.
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