Palynostratigraphy of the Chapada Group and its significance in the Devonian stratigraphy of the Paraná Basin,south Brazil |
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| Authors: | Yngve Grahn Paula Mendlowicz Mauller Egberto Pereira Stanislas Loboziak |
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| Institution: | 1. FGUNPP “Geologorazvedka”, Knipovich str., 11, block 2, Saint-Petersburg 191019, Russia;2. Institute of Geology, Russian Academy of Sciences, Pyzhevsky per. 7, Moscow 119017, Russia;3. Kazan (Volga Region) Federal University, Kremlevskaya ul., 18, 420008 Kazan, Russia;4. Evo-Eco-Paleo, UMR 8198 CNRS, Université des Sciences et Technologies de Lille, Sciences de la Terre, Lille, France;5. Department of Animal and Plant Sciences, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield S10 2TN, UK;1. Centre for Earth Evolution and Dynamics (CEED), University of Oslo, 0316 Oslo, Norway;2. Geodynamics, Geological Survey of Norway, 7040 Trondheim, Norway;3. School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa;4. Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK;1. Universidade do Vale do Rio dos Sinos, Programa de Pós-Graduação em Geologia, Av. Unisinos, 950, Cristo Rei, 93022-000 São Leopoldo, RS, Caixa-postal: 275, Brazil;2. Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, United States of America;3. Universidade Estadual de Ponta Grossa, Departamento de Geociências, Av. Carlos Cavalcanti 9.500, Uvaranas, 84010-919 Ponta Grossa, Paraná state, Brazil;4. Museu Nacional - UFRJ, Departamento de Geologia e Paleontologia, Parque Quinta da Boa Vista, sem número, São Cristóvão, 20940040 Rio de Janeiro, RJ, Brazil;5. Universidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Ciências de Bauru, Departamento de Ciências Biológicas, UNESP, Av. Eng. Luiz Edmundo Carrijo Coube, s/n, 17033-360 Bauru, SP, Brazil;6. Universidade Federal do Rio Grande do Sul, Instituto de Geociências, Av. Bento Gonçalves 9500, Bloco I, Prédio 43113, Campus do Vale, 91509-900 Porto Alegre, RS, Brazil |
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| Abstract: | The Alto Garças Sub-basin in the northern part of the Paraná Basin evolved differently from the Apucarana Sub-basin in the south. The marine environment was shallower in the Alto Garças Sub-basin, which contains proportionately more silty and arenaceous rocks. The formations and members defined in the Apucarana Sub-basin are therefore difficult to apply in the Alto Garças Sub-basin, where the Chapada Group (units 1–4) is more applicable. An integrated miospore and chitinozoan biozonation of the Chapada Group facilitates direct correlation between the Chapada Group’s units and the classical formations of the Paraná Basin as defined in the Apucarana Sub-basin. The Furnas Formation and Chapada unit 1 constitute the same lithostratigraphic unit. Beds with rhyniophytes in the uppermost part of the Furnas Formation contain palynomorphs representative of the Si phylozone within the MN spore Zone (late Lochkovian), and the rhyniophyte beds occupy the same stratigraphic interval within Chapada unit 1 (the Lochkovian of the Paraná Basin lacks chitinozoans). The lower part of Chapada unit 2 contains spores of the PoW Su spore Zone and chitinozoans of the Ramochitina magnifica and Ancyrochitina pachycerata zones, together indicating a late Pragian–early Emsian age-span. The upper part of Chapada unit 2 corresponds to the GS (AP) and Per (AD pre-Lem) spore Zones, and chitinozoans of the Ancyrochitina parisi, the informal Ancyrochitina varispinosa and Alpenachitina eisenacki chitinozoan zones, thus suggestive of a late Emsian – earliest Givetian age-span. Unit 3 is a proximal and lateral facies equivalent of the upper part of unit 2. The lower part of unit 4 includes spores typical of the early Givetian Lli (AD Lem) spore Zone and chitinozoans of the Ramochitina stiphrospinata chitinozoan Zone; the uppermost (early late Frasnian) part contains spores of the lower BMu (IV) spore Zone and chitinozoans of the Lagenochitina avelinoi chitinozoan Zone. The sandstones of unit 3 were inundated during the earliest Givetian, and the resultant flooding surface marks the base of unit 4 basin-wide. Clearly, the two sub-basins were distinct depositional centers during the Devonian. |
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