Chapter 51 The glaciogenic Jequitaí Formation, southeastern Brazil
| Autor: | Alexandre Uhlein, Marcel Auguste Dardenne, Roland Trompette, C. J. S. Alvarenga |
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| Rok vydání: | 2011 |
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| Zdroj: | Geological Society, London, Memoirs. 36:541-546 |
| ISSN: | 2041-4722 0435-4052 |
| Popis: | Glaciogenic deposits of the Jequitai Formation (Fm.) are well exposed along the margins of the Serra do Cabral on the Sao Francisco Craton, southeastern Brazil. The Jequitai Formation is thin (0–150 m thick), lenticular and overlies the Espinhaco Supergroup on a discrete unconformity. Sandstones show subglacial erosional structures such as grooved and striated pavements oriented ENE–WSW. The Jequitai Fm. consists of massive and stratified diamictites with granules, pebbles and boulders of gneiss, granite, quartzite and carbonate. At the base, the diamictites are massive, whereas the upper part contains many alternating beds of clast-rich and -poor diamictites. They also contain discontinuous, fine-grained sandstones and a few laminated siltstone–mudstone intercalations. This diamictite association indicates glaciomarine sedimentation. The Jequitai Fm. covers the Sao Francisco cratonic domain and its equivalent extends eastward over the Aracuai fold belt where it is part of the metasedimentary Macaubas Group, a thick Neoproterozoic unit with metadiamictites, quartzites and schists. The diamictite–turbidite association of the Macaubas Group was deposited on the border of the Pan-African–Brasiliano rift as gravity flows. |
| Databáze: | OpenAIRE |
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