Produção Nacional
Redefinição do Grupo Bom Jardim (Neoproterozóico Iii) em sua área-tipo: litoestratigrafia, evolução paleoambiental e contexto tectônico
2003; Sociedade Brasileira de Geologia; Volume: 33; Issue: 4 Linguagem: Inglês
10.5327/rbg.v33i4.1081
ISSN2317-4889
AutoresLiliane Janikian, Renato Paes de Almeida, Antônio Romalino Santos Fragoso-Cesar, Gélson Luís Fambrini,
Tópico(s)Paleontology and Stratigraphy of Fossils
ResumoThe Camaqua Group is composed of sedimentary and volcanogenic successions that crop out in the south-central portion of the Rio Grande do Sul State (southern Brazil). This supergroup is partially covered by Parana Basin units and has been divided into sub-basins by the uplift of basement highs. This post-depositional tectonic segmentation, and the lithologic similarity among sedimentary successions of different stratigraphic levels makes it difficult to establish a formal lithostratigraphic column of the Bom Jardim Group without detailed field work. This paper presents a review of the lithostratigraphy of the Bom Jardim Work in its type-area, constituted by siliclastic, volcanic (basalts, andesites and rhyolites) and volcaniclastic rocks grouped in three units, with transitional contacts among each other. Cerro da Angelica Formation: rhythmic intercalation of sandstones, siltstones and claystones, as well as pebbly sandstones and minor volcaniclastic rocks (peperites), formed in sub-lacustrine fans and overlying deltaic systems. Hilario Formation: volcanic rocks of basic, intermediate and acid composition (basalts, latite-basalts, latites, andesites and rhyolites) placed in subaquatic environments, and minor pyroclastic rocks (lapilli-tuffs and coarse-grained lithic and vitric tuffs) placed by gravity flows or settled in water. Picada das Gracas Formation: rhythmic layers of fine-grained sandstones, siltstones and claystones formed in pro-delta environments, overlain by a thick succession of conglomerates and pebbly sandstones of proximal fan-deltas. Fluvial and fluvial-dominated deposits occur at the top of the unit.
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