Difference between revisions of "Irati Formation"
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| − | The Irati Formantion was deposited during the Gondwana I Supersequence, in the Permian, Artiskian age (278.4 ± 2.2 Ma until 275.6 ± 0.7 Ma | + | {{Wiki Write Off Entry |
| − | + | |image=AAPG-WIKI-Write-off.jpg | |
| − | + | |student chapter=Federal University of Rio Grande do Sul | |
| + | |competition=June 2015 | ||
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| + | The Irati Formantion was deposited during the Gondwana I Supersequence, in the Permian, Artiskian age (278.4 ± 2.2 Ma until 275.6 ± 0.7 Ma)<ref name=Santos_R._V._et_al.>Santos, R.V., Souza, P.A., de Alvarenga, C.J.S., Dantas, E.L., Pimentel, M.M., de Oliveira, C.G., & de Araújo, L.M. (2006). Shrimp U–Pb zircon dating and palynology of bentonitic layers from the Permian Irati Formation, Paraná Basin, Brazil. Gondwana Research 9(4): 456- 463.</ref> it recorded the transition between the marine influence of the Pantalassa paleo-ocean in the Parana Basin to continental deposition. It preserves the evolution of the Gulf of Irati-Whitehill, which was an epicontinental sea of a wide extension, with evidence for anoxic ([[:File:Paleogeographic setting of the restricted Irati-Whitehill Sea.jpg|Figure 1]]).<ref name=Lavina_E._L.,_1991>Lavina, E.L., 1991. Geologia sedimentar e paleogeografia do Neopermiano e Eotriássico (intervalo Kazaniano-Scythiano) da Bacia do Paraná. Porto Alegre, 333 p. Tese de Doutorado, Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul.</ref><ref name=Milani_E._J.,_2007b>Milani, E.J., Melo, J.H.G., Souza, P.A., Fernandes, L.A., França, A.B., 2007b. Bacia do Paraná. Boletim de Geociências da PETROBRAS, Rio de Janeiro, 15(2): 265–287.</ref> | ||
At this time, the Paraná Basin was in a "Sag tectonic style", with a very slow subsidence rate, within a marine ramp system of an inner basin of mixed origin (siliclastic and carbonates), with paralic conditions, alternating with storm dominated conditions. | At this time, the Paraná Basin was in a "Sag tectonic style", with a very slow subsidence rate, within a marine ramp system of an inner basin of mixed origin (siliclastic and carbonates), with paralic conditions, alternating with storm dominated conditions. | ||
| − | These factors inhibited sandstones deposition, which occurred with low accumulation rates, as thin siliciclastic sediments interbedded with organic rich beds and carbonates. Therefore, grey siltstones and grey bituminous shales layers were preserved, interbedded with marl, calcareous rocks and thin mudstones. The configuration of the Irati Formation facies can be divided into the Taquaral and Assistencia Members ([[:file:Sedimentary cycles of Irati Formation | + | These factors inhibited sandstones deposition, which occurred with low accumulation rates, as thin siliciclastic sediments interbedded with organic rich beds and carbonates. Therefore, grey siltstones and grey bituminous shales layers were preserved, interbedded with marl, calcareous rocks and thin mudstones. The configuration of the Irati Formation facies can be divided into the Taquaral and Assistencia Members ([[:file:Sedimentary cycles of Irati Formation .png|Figure 2]]), according to Milani<ref name=Milani_2007a>Milani, E. J., França, A.B., Medeiros R.Á., 2007a. Rochas geradoras e rochas-reservatório da Bacia do Paraná, faixa oriental de afloramentos, Estado do Paraná. Boletim de Geociências da PETROBRAS, Rio de Janeiro, 15( 1): 135-162.</ref>. |
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| − | The Irati Formation contains a lot of fossils, which are also found in related basins, such as the Mangrullo Formation in Uruguay and Whitehill Formation in the south of Africa | + | The Irati Formation contains a lot of fossils, which are also found in related basins, such as the Mangrullo Formation in Uruguay and Whitehill Formation in the south of Africa.<ref name=Lavina_E._L.,_1991 /> This allowed Alfred Lothar Wegener to use a specific fossil, a Mesosaurus reptile, as evidence of Continental Drift. This theory began a revolution in our concept of the term "deep" geologic time. |
| + | <gallery mode=packed heights=300px widths=300px> | ||
| + | file:Paleogeographic setting of the restricted Irati-Whitehill Sea.jpg|Figure 1. Paleogeographic setting of the restricted Irati-Whitehill Sea<ref name=Milani_2007a /> | ||
| + | file:Sedimentary cycles of Irati Formation .png|Figure 2. Sedimentary cycles of Irati Formation (Milani E. J., et al, 2007a)<ref name=Milani_2007a /> | ||
| + | </gallery> | ||
==References== | ==References== | ||
{{reflist}} | {{reflist}} | ||
Revision as of 13:17, 15 July 2015
| Wiki Write-Off Entry | |
|---|---|
| |
| Student Chapter | Federal University of Rio Grande do Sul |
| Competition | June 2015 |
The Irati Formantion was deposited during the Gondwana I Supersequence, in the Permian, Artiskian age (278.4 ± 2.2 Ma until 275.6 ± 0.7 Ma)[1] it recorded the transition between the marine influence of the Pantalassa paleo-ocean in the Parana Basin to continental deposition. It preserves the evolution of the Gulf of Irati-Whitehill, which was an epicontinental sea of a wide extension, with evidence for anoxic (Figure 1).[2][3]
At this time, the Paraná Basin was in a "Sag tectonic style", with a very slow subsidence rate, within a marine ramp system of an inner basin of mixed origin (siliclastic and carbonates), with paralic conditions, alternating with storm dominated conditions.
These factors inhibited sandstones deposition, which occurred with low accumulation rates, as thin siliciclastic sediments interbedded with organic rich beds and carbonates. Therefore, grey siltstones and grey bituminous shales layers were preserved, interbedded with marl, calcareous rocks and thin mudstones. The configuration of the Irati Formation facies can be divided into the Taquaral and Assistencia Members (Figure 2), according to Milani[4].
The Irati Formation contains a lot of fossils, which are also found in related basins, such as the Mangrullo Formation in Uruguay and Whitehill Formation in the south of Africa.[2] This allowed Alfred Lothar Wegener to use a specific fossil, a Mesosaurus reptile, as evidence of Continental Drift. This theory began a revolution in our concept of the term "deep" geologic time.
Figure 1. Paleogeographic setting of the restricted Irati-Whitehill Sea[4]
Figure 2. Sedimentary cycles of Irati Formation (Milani E. J., et al, 2007a)[4]
References
- ↑ Santos, R.V., Souza, P.A., de Alvarenga, C.J.S., Dantas, E.L., Pimentel, M.M., de Oliveira, C.G., & de Araújo, L.M. (2006). Shrimp U–Pb zircon dating and palynology of bentonitic layers from the Permian Irati Formation, Paraná Basin, Brazil. Gondwana Research 9(4): 456- 463.
- ↑ 2.0 2.1 Lavina, E.L., 1991. Geologia sedimentar e paleogeografia do Neopermiano e Eotriássico (intervalo Kazaniano-Scythiano) da Bacia do Paraná. Porto Alegre, 333 p. Tese de Doutorado, Programa de Pós-Graduação em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul.
- ↑ Milani, E.J., Melo, J.H.G., Souza, P.A., Fernandes, L.A., França, A.B., 2007b. Bacia do Paraná. Boletim de Geociências da PETROBRAS, Rio de Janeiro, 15(2): 265–287.
- ↑ 4.0 4.1 4.2 Milani, E. J., França, A.B., Medeiros R.Á., 2007a. Rochas geradoras e rochas-reservatório da Bacia do Paraná, faixa oriental de afloramentos, Estado do Paraná. Boletim de Geociências da PETROBRAS, Rio de Janeiro, 15( 1): 135-162.