The Taquaral Member, Irati Formation (Paraná Basin, Permian): a synthesis of paleontological studies

Introduction

The Paraná Basin is a intracratonic basin located in southernmost Brazil, Uruguay and parts of Paraguay and Argentina. The basin covers a surface area of about 1,700,000 km2, has a present NE-SW elongated shape, and is approximately 1750 km long and 900 km wide. Late Paleozoic rocks along the eastern border of the Paraná Basin in east-central São Paulo state, southeastern Brazil, are represented, from the base up, by the Tubarão Supergroup (Upper Carboniferous to Permian), including the Itararé Group and the Tatuí Formation, and the Passa Dois Group (Permian), consisting of the Irati and Corumbataí Formations (Holz et al., 2010Holz, M.; França, A.B.; Souza, P.A.; Lannuzzi, R. & Rohn, R. (2010). A stratigraphic chart of the Late Carboniferous/Permian succession of the eastern border of the Paraná Basin, Brazil, South America. Journal of South American Earth Sciences, 29: 381-399. https://doi.org/10.1016/j.jsames.2009.04.004 ).

The term Irati was initially proposed by White (1906)White, I.C. (1906). Geology of south Brazil. Science, 24(612): 377-379. https://doi.org/10.1126/science.24.612.377 as “black schisto”, rich in oil, then registered in the states of São Paulo and Paraná. Subsequently the research was extended to the entire Brazilian part of the Paraná Basin (Fig.1), White’s proposal resulted in many stratigraphic researches, until reaching Barbosa & Gomes (1958)Barbosa, O. & Gomes, F.A. (1958). Pesquisa de petróleo na bacia do rio Corumbataí. Rio de Janeiro, Boletim do DNPM/DGM, 171, 40 pp. who subdivided the Irati into two members: Taquaral (lower) and Assistência (upper). This stratigraphic division was accepted by most of the researchers (Holz et al., 2010Holz, M.; França, A.B.; Souza, P.A.; Lannuzzi, R. & Rohn, R. (2010). A stratigraphic chart of the Late Carboniferous/Permian succession of the eastern border of the Paraná Basin, Brazil, South America. Journal of South American Earth Sciences, 29: 381-399. https://doi.org/10.1016/j.jsames.2009.04.004 ; Chahud et al., 2010aChahud, A.; Duque, J.M. & Petri, S. (2010a). Consideraciones geológicas y paleontológicas de las formaciones Tatuí e Iratí (Pérmico), Cuenca de Paraná, Brasil. Geología Colombiana, 35: 36-49., 2010bChahud, A.; Fairchild, T.R. & Petri, S. (2010b). Chondrichthyans from the base of the Irati Formation Permian, Parana Basin), São Paulo, Brazil. Gondwana Research, 18: 528-537. https://doi.org/10.1016/j.gr.2010.01.006 , 2012Chahud, A.; Pacheco, M.L.A.F.; Meira, F.E.; Romero, G.R. & Petri, S. (2012). Paleontology and depositional environments of the Tatuí and Irati formations (Permian) in the Ponte Nova Farm, Ipeúna, state of São Paulo. Revista Brasileira de Geociências, 42(1): 198-212. https://doi.org/10.25249/0375-7536.2012421198212 ).

Figure 1. A) Map of the Paraná Basin (gray region) in map of South America; B) Outcrop belt of the Irati Formation (adapted from and ).

Hachiro et al. (1993)Hachiro, J.; Coimbra, A. & Matos, S.L.F. (1993). O caráter cronoestratigráfico da unidade Irati. In: I Simpósio de Cronoestratigrafia da Bacia do Paraná. Rio Claro, FUNDUNESP. Boletim de Resumos, 62-63. and Hachiro (1996)Hachiro, J. (1996). O Subgrupo Irati (Neopermiano) da Bacia do Paraná. PhD Thesis. São Paulo: Instituto de Geociências-USP, 196 pp. proposed upgrade the Irati Formation to Subgroup and the Taquaral and Assistência members to formations. This proposition was not properly formalized, due to mapping problems, so the present researchers rather favor to keep the proposal of Barbosa & Gomes (1958)Barbosa, O. & Gomes, F.A. (1958). Pesquisa de petróleo na bacia do rio Corumbataí. Rio de Janeiro, Boletim do DNPM/DGM, 171, 40 pp..

Absolute dating on Assistência beds by Santos et al. (2006)Santos, R. V.; Souza, P.A.; Alvarenga, C.J.S.; Dantas, E.L.; Pimentel, E.L.; Oliveira, C.G. & Araújo, L.M. (2006). Shrimp U-Pb Zircon Dating and Palynology of Bentonitic Layers from the Permian Irati Formation Parana Basin, Brazil. Gondwana Research, 9: 456-463. https://doi.org/10.1016/j.gr.2005.12.001 and Rocha-Campos et al. (2007)Rocha-Campos, A.C.; Basei, M.A.S.; Nutman, A.P.; Santos, P.R. (2007). SHRIMP U-Pb zircon ages of the late Paleozoic sedimentary sequence, Paraná Basin, Brazil. IV Simpósio de Cronoestratigrafia da Bacia Do Paraná. Búzios: Boletim de Resumos, 33. yielded Cisuralian ages, between 279 - 276Ma (Kungurian).

The Taquaral Member occurs irregularly in the Paraná Basin, absent in some places and with thickness close to 30 m in others (Hachiro, 1996Hachiro, J. (1996). O Subgrupo Irati (Neopermiano) da Bacia do Paraná. PhD Thesis. São Paulo: Instituto de Geociências-USP, 196 pp.; Chahud, 2007Chahud, A. (2007). Paleontologia de Vertebrados da Transição entre os grupos Tubarão e Passa Dois no Centro-Leste do Estado de São Paulo. Master Dissertation, Instituto de Geociências da Universidade de São Paulo, Brazil., 2011Chahud, A. (2011). Geologia e paleontologia das formações Tatuí e Irati no centro-leste do Estado de São Paulo. PhD Thesis. Instituto de Geociências da Universidade de São Paulo, Brazil, 299 pp.). Dark gray and non-bituminous siltstones and mudstones are the main lithologies (Fig. 2). Three facies are distinguished based on lithologies, fossils and geographic areas.

Figure 2. Sketched columnar section of the Taquaral Member, Irati Formation as occurring at the States of São Paulo and Paraná. 1) Sandy-facies; 2) Silty-shale facies; 3) Carbonate layers.

The first facies is defined by lenticular layers of conglomeratic sandstones, with granules and chert pebbles. Maximum thickness is one meter, normally 10 to 40 cm. These lithosomas are disposed irregularly, without any order of deposition of granulometry. Hachiro (1996)Hachiro, J. (1996). O Subgrupo Irati (Neopermiano) da Bacia do Paraná. PhD Thesis. São Paulo: Instituto de Geociências-USP, 196 pp. distinguished several facies on granulometric basis. Diversified Chondrichthyes were studied by Chahud & Petri (2008aChahud, A. & Petri, S. (2008a). Chondrichthyes no Membro Taquaral, base da Formação Itati, no centro-leste do Estado de São Paulo, Brasil. Revista de Geologia, 21: 169-179., 2009aChahud, A. & Petri, S. (2009a). Novos Xenacanthidae (Chondrichthyes, Elasmobranchii) da base do Membro Taquaral, Formação Irati, Permiano da Bacia do Paraná. Revista do Instituto Geológico, 30(1/2), 19-24. https://doi.org/10.5935/0100-929X.20090002 , 2010bChahud, A. & Petri, S. (2010b). Contribuição ao estudo do Petalodonte Itapyrodus punctatus Silva Santos, 1990. Revista de Biologia e Ciências da Terra, 10: 67-75., 2010cChahud, A. & Petri, S. (2010c). O tubarão Taquaralodus albuquerquei (Silva Santos, 1946) do Membro Taquaral (Permiano, Formação Irati) no Estado de São Paulo. Acta Biologica Paranaense, 39: 1-17. https://doi.org/10.5380/abpr.v39i0.20236 , 2012aChahud, A. & Petri, S. (2012a). Levantamento dos cladodontes sul-americanos e novos espécimes do Membro Taquaral (Formação Irati, Permiano), Bacia do Paraná. Boletim Paranaense de Geociências, 66-67: 23-29. https://doi.org/10.5380/geo.v67i0.17271 ).

The second facies is an almost homogeneous non bituminous silty-shale, generally plane-parallel laminated, no sedimentary structures. The thickness range from 5 to 30 meters. The crustacean Clarkecaris Clarke 1920 is known only in this facies.

A third facies represented by fine carbonate layers can be observed in the thichest stratigraphic sections of the Taquaral Member, in the State of Paraná. The thickness of these carbonates around 30 cm. It is composed of dolomitic micrites, occasionally containing bivalves, located in the upper half of the unit (Hachiro, 1996Hachiro, J. (1996). O Subgrupo Irati (Neopermiano) da Bacia do Paraná. PhD Thesis. São Paulo: Instituto de Geociências-USP, 196 pp.; Lages, 2004Lages, L.C. 2004. A Formação Irati (Grupo Passa Dois, Permiano, Bacia do Paraná) no furo de sondagem FP-01-PR (Sapopema, PR). Master Dissertation. Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Rio Claro, Brazil, 117 pp.; Matos et al. 2017Matos, S.A.; Warren, L.V.; Varejão, F.G.; Assine, M.L. & Simões, M.G. (2017). Permian endemic bivalves of the “Irati anoxic event”, Paraná Basin, Brazil: Taphonomical, paleogeographical and evolutionary implications. Palaeogeography, Palaeoclimatology, Palaeoecology, 469: 18-33. https://doi.org/10.1016/j.palaeo.2016.12.043 ).

The Taquaral Member has recently been the target of numerous paleontological and sedimentological contributions, with emphasis on the study of facies, vertebrates, arthropods, ichnofossils, palynology and taphonomy (Lages, 2004Lages, L.C. 2004. A Formação Irati (Grupo Passa Dois, Permiano, Bacia do Paraná) no furo de sondagem FP-01-PR (Sapopema, PR). Master Dissertation. Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Rio Claro, Brazil, 117 pp.; Holz et al. 2010Holz, M.; França, A.B.; Souza, P.A.; Lannuzzi, R. & Rohn, R. (2010). A stratigraphic chart of the Late Carboniferous/Permian succession of the eastern border of the Paraná Basin, Brazil, South America. Journal of South American Earth Sciences, 29: 381-399. https://doi.org/10.1016/j.jsames.2009.04.004 ; Chahud et al. 2010bChahud, A.; Fairchild, T.R. & Petri, S. (2010b). Chondrichthyans from the base of the Irati Formation Permian, Parana Basin), São Paulo, Brazil. Gondwana Research, 18: 528-537. https://doi.org/10.1016/j.gr.2010.01.006 ; Chahud & Petri, 2010aChahud, A. & Petri, S. (2010a). Anfíbio e Paleonisciformes da Porção Basal do Membro Taquaral, Formação Irati (Permiano), Estado de São Paulo, Brasil. Geologia USP, Série Científica, 10(1): 29-37. https://doi.org/10.5327/Z1519-874X2010000100003 ; 2015bChahud, A. & Petri, S. (2015b). Geology and Taphonomy from the Base of the Taquaral Member, Irati Formation (Permian, Paraná Basin), Brazil. Acta Geologica Polonica, 65(3): 379-387. https://doi.org/10.1515/agp-2015-0017 ). A synthesis of these contributions is the main goal of this contribution.

Paleontological Studies

⌅

Micropaleontology and Paleopalynology

⌅

Previous references on microfossils from Taquaral, are scarce and few illustrated. Lages (2004)Lages, L.C. 2004. A Formação Irati (Grupo Passa Dois, Permiano, Bacia do Paraná) no furo de sondagem FP-01-PR (Sapopema, PR). Master Dissertation. Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Rio Claro, Brazil, 117 pp. issued the main palynological study on drilled cores. The Taquaral Member is characterized by a great diversity of pollens: Alisporites Daugherty, 1941; Lueckisporites Potonié & Klaus, 1954; Striatopodocarpites Sedova, 1956 and Vittatina Mildenhall, 1994 and spores: Punctatisporites Potonié & Kremp, 1954 and Cirratriradites Wilson & Coe 1940.

The biostratigraphy of the Taquaral Member allow some paleoenvironmental interpretations.

The acritarchs genera present in the beds are related to an environment wit salinity (Grice et al., 2005Grice, K.; Twitchett, R.J.; Alexander, R.; Foster, C.B. & Looy, C. (2005). A potential biomarker for the Permian-Triassic ecological crisis. Earth and Planetary Science Letters, 236: 315-321. https://doi.org/10.1016/j.epsl.2005.05.008 ). Marasco et al. (1993)Marasco, S.A.; Souza, P.A. & Pires, F.A. (1993). Ocorrência de paleomicroplâncton marinho (Acritarcha) associado a ictiofósseis na base do Membro Taquaral, Formação Iratí (Permiano Superior da bacia do Paraná), região de Itapetininga, Estado de São Paulo. XIII Congresso Brasileiro de Paleontologia e I Simpósio Paleontológico do Cone Sul, São Leopoldo. reported only the genus Micrhystridium in the sandy-facies in the State of São Paulo while Cardoso (2010)Cardoso, T.R.M. (2010). Registro marinho no Membro Taquaral (Formação Irati), Permiano Superior da Bacia do Paraná, Brasil. XIII Simpósio Brasileiro de Paleobotânica e Palinologia, Salvador, Bahia, 143. reported four genera in the silty-shale facies of the State of Paraná (Fig. 1), Micrhystridium Deflandre, 1938; Veryhachium Deunff, 1954; Tasmanites Newton, 1875 and Deusilites Hemer & Nygreen, 1967.

Lei et al. (2013)Lei, Y.; Servais, T.; Feng, Q.L. & He, W.H. (2013). Latest Permian acritarchs from South China and the Micrhystridium/Veryhachium complex revisited. Palynology, 37: 325-344. https://doi.org/10.1080/01916122.2013.793625 were not able to uphold a clear distinction between Micrhystridium and Veryhachium calling both genera as a complex, though they cited in China, Late Permian, different species as Micrhystridium and Veryhachium. In China they occur in different Late Permian palaeoenvironments from nearshore to continental slopes. The poor taxa representation on Taquaral, might be caused by a rather isolated lagoon, where the sea phytoplankton would easily enter with the tides.

Lages (2004)Lages, L.C. 2004. A Formação Irati (Grupo Passa Dois, Permiano, Bacia do Paraná) no furo de sondagem FP-01-PR (Sapopema, PR). Master Dissertation. Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Rio Claro, Brazil, 117 pp. observed the typical freshwater algae, Botryococcus Kützing, 1849, in Taquaral Member, but the presence of this genus only indicates that the environment received freshwater in the system.

Another microfossil observed was identified by Mezzalira (1980)Mezzalira, S. (1980). Bioestratigrafia do Grupo Passa Dois no Estado de São Paulo. Revista do Instituto Geológico, 1(1): 15-34. https://doi.org/10.5935/0100-929X.19800003 , a monoaxial spongy spicules associated with fish and crustacean remains.

Molluscs

⌅

The molluscs, in despite of hard shells resistant to transport, are not frequently found in the Irati Formation.

Bivalves are scarcely mentioned in Taquaral deposits, but when uncommon calcareous thin layers interbed with shales, then lots of specimens, with 5 mm long, were found in the outcrops (Kazubek & Simoes, 2002Kazubek, M.F. & Simoes, M.G. (2002). The lost fauna unearthed: Permian bivalves of the Irati Formation (Passa Dois Group), Paraná Basin, Brazil. Paleo-2002, Porto Alegre. Paleontologia em Destaque, 40: 31., 2003Kazubek, M.F. & Simoes, M.G. (2003). Permian bivalves of the Irati Formation (Passa Dois Group, Paraná Basin) and their paleoecological significance. XVIII Congresso Brasileiro de Paleontologia. Brasília. Boletim de Resumos, 161.; Rohn et al, 2003Rohn, R.; Lages, L.C. & Pennatti, J.R.R. (2003). Litofácies da Formação Irati no furo de sondagem FP-01-PR (Permiano, borda leste da Bacia do Paraná). Congresso Brasileiro de PandD em Petróleo and Gás, Rio de Janeiro, 2: 1-6.; Lages, 2004Lages, L.C. 2004. A Formação Irati (Grupo Passa Dois, Permiano, Bacia do Paraná) no furo de sondagem FP-01-PR (Sapopema, PR). Master Dissertation. Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Rio Claro, Brazil, 117 pp.). Matos et al. (2017)Matos, S.A.; Warren, L.V.; Varejão, F.G.; Assine, M.L. & Simões, M.G. (2017). Permian endemic bivalves of the “Irati anoxic event”, Paraná Basin, Brazil: Taphonomical, paleogeographical and evolutionary implications. Palaeogeography, Palaeoclimatology, Palaeoecology, 469: 18-33. https://doi.org/10.1016/j.palaeo.2016.12.043 studied their taxonomy and identified a poor fauna, composed only of the genera Runnegariella Simões & Anelli, 1995 and Plesiocyprinella Holdhaus, 1918 and some indeterminate forms densely concentrated.

Arthropods

⌅

The arthropods are the most well preserved fossils in the Taquaral Member. All the fossils are from the silty-shale facies. The most common species is Clarkecaris brasilicus. It is easily recognized by a narrow, elongated body composed of 8 narrow pustular thoracic somites, 6 distinctly wider abdominal somites, without pustulation and two large pterygostomial spines. It is endemic in Taquaral Member of the states of São Paulo and Paraná (Fig. 1). According to Brooks (1962)Brooks, H.K. (1962). On the fossil Anaspidacea, a revision of the classification of the Syncarida. Crustaceana, 4: 229-242. https://doi.org/10.1163/156854062X00364 this genus belongs to the family, Clarkecarididae, within the order Anaspidacea, but without relation to other families.

The paleoenvironment inhabited by Clarkecaris is controversial, whether inhabited saline or freshwater paleoenvironments. Beurlen (1931)Beurlen, K. (1931). Crustaceenreste aus den Mesosaurierschiten (Unterperm) Von Brasilien (S. Paulo). Palaeontologische Zeitschr, 13: 35-50. https://doi.org/10.1007/BF03043321 suggested freshwater, based on the recent Anaspidacea. Mezzalira (1952)Mezzalira, S. (1952). Clarkecaris, novo gênero de crustáceo Syncarida do Permiano. Boletim da Sociedade Brasileira de Geologia, 1(1): 46-52. discussed the paleoenvironment of Clarkecaris, but although phylogenetically close genus Anaspidites Chilton, 1929, prefer freshwater. Beurlen (1931)Beurlen, K. (1931). Crustaceenreste aus den Mesosaurierschiten (Unterperm) Von Brasilien (S. Paulo). Palaeontologische Zeitschr, 13: 35-50. https://doi.org/10.1007/BF03043321 and Mezzalira (1952)Mezzalira, S. (1952). Clarkecaris, novo gênero de crustáceo Syncarida do Permiano. Boletim da Sociedade Brasileira de Geologia, 1(1): 46-52. agreed that this genus probably inhabited coastal regions rather than the deepest part of the Paraná Basin so they are present in regions closer to the basin border.

Clarkecaris brasilicus was compared with the Paleocaridacea of the Carboniferous, Squillites Scott, 1938 and Palaeocaris Schram, 1984. According to Schram & Schram (1974)Schram, J.M. & Schram, F.R. (1974). Squillites spinosus Scott 1938 (Syncarida Malascostraca) from the Mississipian Heath shale of Central Montana. Journal of Paleontology, 48(1): 95-104.Clarkecaris have features transitional between the more primitive Paleocaridacea and the living Anaspidacea of the genus Anaspidites. The Squillites paleoenvironment is doubtful, because its remains have been found associated with freshwater and euryhaline fossils. Other genus, Palaeocaris has long been considered freshwater, but fossils associated with estuarine paleoenvironments or with variable salinity have been found (Schultze, 2009Schultze, H.P. (2009). Interpretation of marine and freshwater paleoenvironments in Permo-Carboniferous deposits. Palaeogeography, Palaeoclimatology, Palaeoecology, 281: 126-136. https://doi.org/10.1016/j.palaeo.2009.07.017 ). Schram & Schram (1974)Schram, J.M. & Schram, F.R. (1974). Squillites spinosus Scott 1938 (Syncarida Malascostraca) from the Mississipian Heath shale of Central Montana. Journal of Paleontology, 48(1): 95-104. and Schram (1977)Schram, F.R. (1977). Paleozoogeography of Late Paleozoic and Triassic Malacostraca. Systematic Zoology, 26(4): 367-379. https://doi.org/10.2307/2412793 considered the earliest Devonian Syncarids, marine, passing in the Early Carboniferous to less saline and freshwaters. Many Syncarida Anaspidacea groups have restricted themselves to the South American and Australian continents; therefore Gondwana is their refuge at the end of the Paleozoic.

Another crustacean, very rare, is represented only by caudal uropods. The first citations were from Foehringer & Langer, (2003Foehringer, K.J.A. & Langer, M.C. (2003). A descoberta de um decápodo reptântio (Crustacea, Malacostracea) da Formação Irati (Permiano da Bacia do Paraná). XVIII Congresso Brasileiro de Paleontologia. Brasília, Boletim de Resumos, 132., 2004)Foehringer, K.J.A. & Langer, M.C. (2004). Relações do crustáceo reptântio da Formação Irati (Permiano Superior). PALEO 2004. São Carlos. Boletim de Resumos, 12. who identified them as chelae, subsequently correctly identified by Chahud & Petri (2013b)Chahud, A. & Petri, S. (2013b). The silty shale Taquaral Member of the early Permian Irati Formation (Paraná Basin, Brazil). Paleontology and paleoenvironments. Swiss Journal of Palaeontology, 132: 119-128. https://doi.org/10.1007/s13358-013-0055-1 .

Vertebrates

⌅

Vertebrates remains are found throughout the Taquaral Member, however the greatest abundance and diversification are in the sandy facies. In spite of the great variety and frequence, the fossils are, in general, disarticulated, only teeth, scales, finspines and scattered bones.

Chondrichthyes

⌅

Chondrichthyes are the most diversified group, with spines and teeth of different sizes and states of preservation (Chahud & Petri, 2015aChahud, A. & Petri, S. (2015a). Geologia e Paleontologia da Formação Irati (Eopermiano, Bacia do Paraná) no Rio Passa Cinco, Estado de São Paulo. Brazilian Geographical Journal: Geosciences and Humanities research medium, 6(1): 110-120., 2015bChahud, A. & Petri, S. (2015b). Geology and Taphonomy from the Base of the Taquaral Member, Irati Formation (Permian, Paraná Basin), Brazil. Acta Geologica Polonica, 65(3): 379-387. https://doi.org/10.1515/agp-2015-0017 , Chahud, 2018Chahud, A. (2018). Chondrichthyes Indeterminados do Membro Taquaral (Permiano, Formação Irati) no Estado de São Paulo (Brasil). Acta Biológica Paranaense, 47: 129-141. https://doi.org/10.5380/abpr.v47i0.63771 ).

The dorsal finspines of Elasmobranchii are rare, but it was possible to identify the genera Sphenacanthus Agassiz, 1837; Amelacanthus Maisey, 1982 and indeterminate species (Chahud et al., 2010bChahud, A.; Fairchild, T.R. & Petri, S. (2010b). Chondrichthyans from the base of the Irati Formation Permian, Parana Basin), São Paulo, Brazil. Gondwana Research, 18: 528-537. https://doi.org/10.1016/j.gr.2010.01.006 , 2012Chahud, A.; Pacheco, M.L.A.F.; Meira, F.E.; Romero, G.R. & Petri, S. (2012). Paleontology and depositional environments of the Tatuí and Irati formations (Permian) in the Ponte Nova Farm, Ipeúna, state of São Paulo. Revista Brasileira de Geociências, 42(1): 198-212. https://doi.org/10.25249/0375-7536.2012421198212 ; Chahud & Petri, 2014Chahud, A. & Petri, S. (2014). New chondrichthyans from the Irati Formation (Early Permian, Paraná Basin), Brazil: origin, palaeoenvironmental and palaeogeographical considerations. Proceedings of the Geologists Association, 125: 437-445. https://doi.org/10.1016/j.pgeola.2014.07.006 ).

The Chondrichthyes teeth are the most abundant remains. Among the indeterminate forms, three different cladodonts were recognized (Chahud & Petri, 2012aChahud, A. & Petri, S. (2012a). Levantamento dos cladodontes sul-americanos e novos espécimes do Membro Taquaral (Formação Irati, Permiano), Bacia do Paraná. Boletim Paranaense de Geociências, 66-67: 23-29. https://doi.org/10.5380/geo.v67i0.17271 ).

The Xenacanthiformes are the most abundant elasmobranchs. The most common species is Taquaralodus albuquerquei Silva Santos, 1946 (Silva Santos 1946Silva Santos, R. (1946). Duas novas formas de elasmobranquios do Paleozóico do Meio Norte do Brasil. Anais da Academia Brasileira de Ciências, 18(4): 281-285., Chahud & Petri, 2010cChahud, A. & Petri, S. (2010c). O tubarão Taquaralodus albuquerquei (Silva Santos, 1946) do Membro Taquaral (Permiano, Formação Irati) no Estado de São Paulo. Acta Biologica Paranaense, 39: 1-17. https://doi.org/10.5380/abpr.v39i0.20236 ). This species was first described in the Pedra de Fogo Formation, Parnaíba Basin by Silva Santos (1946)Silva Santos, R. (1946). Duas novas formas de elasmobranquios do Paleozóico do Meio Norte do Brasil. Anais da Academia Brasileira de Ciências, 18(4): 281-285., with the name “Pleuracanthus” albuquerquei. Ragonha (1978)Ragonha, E.W. (1978). Chondrichthyes do Membro Taquaral (Formação Irati) no Estado de São Paulo. Master Dissertation. IGc-USP. São Paulo. Brazil. was the first to identify this species in the Taquaral Member. Ragonha (op. cit.) recognized external morphological differences of “Pleuracanthus”, informally suggesting the genus “Taquaranthus”, but without adequate revision. Chahud & Petri (2010c)Chahud, A. & Petri, S. (2010c). O tubarão Taquaralodus albuquerquei (Silva Santos, 1946) do Membro Taquaral (Permiano, Formação Irati) no Estado de São Paulo. Acta Biologica Paranaense, 39: 1-17. https://doi.org/10.5380/abpr.v39i0.20236 reviewed this species and observed different morphological characteristics from any other genus of Xenacanthiformes, such as cuspids and coronal button, therefore they considered more appropriate a new genus, Taquaralodus.

Other Xenacanthiformes in the sandy facies of the Irati Formation are represented by the genus Xenacanthus Beyrich, 1848 and indeterminate species (Chahud & Petri, 2009bChahud, A. & Petri, S. (2009b). Sarcopterygii do Topo da Formação Tatuí e Base da Formação Irati, Permiano, São Paulo, Brasil. Revista Ung Geociências, 8: 39-46. https://doi.org/10.5380/abpr.v39i0.20236 ).

The oldest occurrence of the genus Orodus in Brazil is from the Taquaral Member, O. ipeunaensis Chahud, Fairchild & Petri, 2010 (Chahud et al. 2010bChahud, A. & Petri, S. (2010b). Contribuição ao estudo do Petalodonte Itapyrodus punctatus Silva Santos, 1990. Revista de Biologia e Ciências da Terra, 10: 67-75.), older than O. milleri Würdig-Maciel, 1975 from the Teresina Formation in southern Brazil (Würdig-Maciel, 1975Würdig-Maciel, N.L. (1975). Ichtiodontes e ichtiodorulitos (Pisces) da Formação Estrada Nova e sua aplicação na estratigrafia do Grupo Passa Dois. Pesquisas, 5: 7-165. https://doi.org/10.22456/1807-9806.21830 , Richter, 2004aRichter, M. (2004a). Late Permian (Guadalupian) shark remains (Chondrichthyes) from the Teresina Formation, Paraná Basin, Southern Brazil. X International Symposium on Early vertebrates/Lower vertebrates, Gramado, 28-29., 2004bRichter, M. (2004b). Distribution of Permian Fishes of Brazil and their palaeoenvironments. 48th Annual Meeting 17th-20th December 2004. Newsletter of the Palaeontological Association, 57: 178.). Only these two species of this genus are recognized in Brazil.

Teeth of two above mentioned species of Chondrichthyes, Taquaralodus albuquerquei and Itapyrodus punctatus Silva Santos, 1990 are described both in Pedra de Fogo and Irati formations (Ragonha, 1978Ragonha, E.W. (1978). Chondrichthyes do Membro Taquaral (Formação Irati) no Estado de São Paulo. Master Dissertation. IGc-USP. São Paulo. Brazil.; Silva Santos, 1990Silva Santos, R. (1990). Paleoictiofáunula da Formação Pedra do Fogo, Nordeste do Brasil: Holocephali-Petalodontidae. Anais da Academia Brasileira de Ciências, (62)4: 347-355.; Chahud & Petri, 2008aChahud, A. & Petri, S. (2008a). Chondrichthyes no Membro Taquaral, base da Formação Itati, no centro-leste do Estado de São Paulo, Brasil. Revista de Geologia, 21: 169-179., 2010cChahud, A. & Petri, S. (2010c). O tubarão Taquaralodus albuquerquei (Silva Santos, 1946) do Membro Taquaral (Permiano, Formação Irati) no Estado de São Paulo. Acta Biologica Paranaense, 39: 1-17. https://doi.org/10.5380/abpr.v39i0.20236 ; Chahud et al., 2010bChahud, A.; Fairchild, T.R. & Petri, S. (2010b). Chondrichthyans from the base of the Irati Formation Permian, Parana Basin), São Paulo, Brazil. Gondwana Research, 18: 528-537. https://doi.org/10.1016/j.gr.2010.01.006 ).

Ragonha (1978)Ragonha, E.W. (1978). Chondrichthyes do Membro Taquaral (Formação Irati) no Estado de São Paulo. Master Dissertation. IGc-USP. São Paulo. Brazil. and Silva Santos (1990)Silva Santos, R. (1990). Paleoictiofáunula da Formação Pedra do Fogo, Nordeste do Brasil: Holocephali-Petalodontidae. Anais da Academia Brasileira de Ciências, (62)4: 347-355. placed Itapyrodus within the Petalodontiformes, however Chahud & Petri (2016)Chahud, A. & Petri, S. (2016). Paleontologia da fácies arenosa do Membro Taquaral (Permiano) no Estado de São Paulo: estado da arte e contribuições adicionais. Geologia USP. Série Científica, 16(3): 105-115. https://doi.org/10.11606/issn.2316-9095.v16i3p105-115 put it in Holocephali, inasmuch new classification of this order is suggested by Lund et al. (2014)Lund, R.; Grogan, E. D. & Fath, M. (2014). On the Relationships of the Petalodontiformes (Chondrichthyes). Paleontological Journal, 48(9): 1030-1043. https://doi.org/10.1134/S0031030114090081 and Grogan et al. (2014)Grogan, E.D.; Lund, R. & Fath, M. (2014). A New Petalodont Chondrichthyan from the Bear Gulch Limestone of Montana, USA, with Reassessment of Netsepoye hawesi and Comments on the Morphology of Holomorphic Petalodonts. Paleontological Journal, 48(9): 1003-1014. https://doi.org/10.1134/S0031030114090044 .

Indeterminate Holocephali were observed from isolated, irregularly shaped teeth, comparable to the genus Itapyrodus at the base of the Taquaral Member.

No Chondrichthyes are known in the silty-shale facies, suggesting that environmental changes restricted these fishes in shallower areas of the basin or in regions that maintained tolerable salinity.

The Holocephali first appeared in the Paraná Basin, in deposits of the lowermost Taquaral Member, so the most probable hypothesis for its origin in the basin would be a link between the Paraná and Parnaíba basins (Chahud & Petri 2014Chahud, A. & Petri, S. (2014). New chondrichthyans from the Irati Formation (Early Permian, Paraná Basin), Brazil: origin, palaeoenvironmental and palaeogeographical considerations. Proceedings of the Geologists Association, 125: 437-445. https://doi.org/10.1016/j.pgeola.2014.07.006 , 2016Chahud, A. & Petri, S. (2016). Paleontologia da fácies arenosa do Membro Taquaral (Permiano) no Estado de São Paulo: estado da arte e contribuições adicionais. Geologia USP. Série Científica, 16(3): 105-115. https://doi.org/10.11606/issn.2316-9095.v16i3p105-115 ).

Palaeonisciformes, Sarcopterygii and tetrapods

⌅

Remains of bony fish are present throughout the Permian of the Paraná Basin. They are the most abundant group of paleovertebrates, but few species have been described, due to the scarcity of articulated specimens.

The Palaeonisciformes are known by teeth, scales and indeterminate bones. Teeth are usually conical and simple; however the size and surface ornamentation are variable in every units of the Paraná Basin (Würdig-Maciel, 1975Würdig-Maciel, N.L. (1975). Ichtiodontes e ichtiodorulitos (Pisces) da Formação Estrada Nova e sua aplicação na estratigrafia do Grupo Passa Dois. Pesquisas, 5: 7-165. https://doi.org/10.22456/1807-9806.21830 , Richter et al., 1985Richter, M.; Piccoli, A.M.M. & Lima, M.C.S. (1985). Variação morfológica de restos de paleoniscídeos (Pisces) no Permiano da Bacia do Paraná. Coletânea de Trabalhos Paleontológicos. DNPM, Série Geologia. Seção de Paleontologia e Estratigrafia. Brasília, 2(27): 111-122., Chahud & Petri, 2008bChahud, A. & Petri, S. (2008b). Registro de paleoniscóides na base do Membro Taquaral, Formação Irati, Permiano da Bacia do Paraná. Revista do Instituto Geológico, 29(1/2): 33-40. https://doi.org/10.5935/0100-929X.20080003 , 2010aChahud, A. & Petri, S. (2010a). Anfíbio e Paleonisciformes da Porção Basal do Membro Taquaral, Formação Irati (Permiano), Estado de São Paulo, Brasil. Geologia USP, Série Científica, 10(1): 29-37. https://doi.org/10.5327/Z1519-874X2010000100003 , Chahud, 2020Chahud, A. (2020). Geologia e paleontologia do Membro Taquaral (Eopermiano) no afloramento do Rio da Cabeça, Estado de São Paulo. Estudos Geológicos (UFPE), 30: 19-30. https://doi.org/10.18190/1980-8208/estudosgeologicos.v30n1p19-30 ). The fossils are more abundant and diversified in the sandy facies (Chahud & Petri, 2008bChahud, A. & Petri, S. (2008b). Registro de paleoniscóides na base do Membro Taquaral, Formação Irati, Permiano da Bacia do Paraná. Revista do Instituto Geológico, 29(1/2): 33-40. https://doi.org/10.5935/0100-929X.20080003 , 2016Chahud, A. & Petri, S. (2016). Paleontologia da fácies arenosa do Membro Taquaral (Permiano) no Estado de São Paulo: estado da arte e contribuições adicionais. Geologia USP. Série Científica, 16(3): 105-115. https://doi.org/10.11606/issn.2316-9095.v16i3p105-115 ) than in silty-shale facies when only small scales and teeth are identified (Chahud & Petri, 2013aChahud, A. & Petri, S. (2013a). Paleontology of Taquaral Member silty shale in the State of São Paulo. Brazilian Journal of Geology, 43: 117-123. https://doi.org/10.5327/Z2317-48892013000100010 , 2013bChahud, A. & Petri, S. (2013b). The silty shale Taquaral Member of the early Permian Irati Formation (Paraná Basin, Brazil). Paleontology and paleoenvironments. Swiss Journal of Palaeontology, 132: 119-128. https://doi.org/10.1007/s13358-013-0055-1 ).

The Sarcopterygii occur in the form of teeth, scales and bony parts. Coelacanthiformes scales are the most common in silty-shale (Chahud & Petri, 2013aChahud, A. & Petri, S. (2013a). Paleontology of Taquaral Member silty shale in the State of São Paulo. Brazilian Journal of Geology, 43: 117-123. https://doi.org/10.5327/Z2317-48892013000100010 , 2013bChahud, A. & Petri, S. (2013b). The silty shale Taquaral Member of the early Permian Irati Formation (Paraná Basin, Brazil). Paleontology and paleoenvironments. Swiss Journal of Palaeontology, 132: 119-128. https://doi.org/10.1007/s13358-013-0055-1 ) and very rare in sandy facies, in which bones and possible teeth are present (Chahud & Petri, 2009bChahud, A. & Petri, S. (2009b). Sarcopterygii do Topo da Formação Tatuí e Base da Formação Irati, Permiano, São Paulo, Brasil. Revista Ung Geociências, 8: 39-46. https://doi.org/10.5380/abpr.v39i0.20236 , 2012bChahud, A. & Petri, S. (2012b). Sarcopterygii do Eopermiano da Bacia do Paraná, Estado de São Paulo. Revista do Instituto Geológico, 33: 57-64. https://doi.org/10.5935/0100-929X.20120011 ). They are rare in sandy facies which may be caused by the fragility of the scales which would not resist the high energy environment characteristic of this facies.

The tetrapods Temnospondyli are present in the sandy facies by teeth, mandibulars fragments (Chahud & Petri, 2010aChahud, A. & Petri, S. (2010a). Anfíbio e Paleonisciformes da Porção Basal do Membro Taquaral, Formação Irati (Permiano), Estado de São Paulo, Brasil. Geologia USP, Série Científica, 10(1): 29-37. https://doi.org/10.5327/Z1519-874X2010000100003 ) and small appendicular bones of probable small species, which may be attributed to Osteolepiformes (Chahud & Petri, 2009bChahud, A. & Petri, S. (2009b). Sarcopterygii do Topo da Formação Tatuí e Base da Formação Irati, Permiano, São Paulo, Brasil. Revista Ung Geociências, 8: 39-46. https://doi.org/10.5380/abpr.v39i0.20236 , 2012bChahud, A. & Petri, S. (2012b). Sarcopterygii do Eopermiano da Bacia do Paraná, Estado de São Paulo. Revista do Instituto Geológico, 33: 57-64. https://doi.org/10.5935/0100-929X.20120011 ).

Taphonomy

⌅

The presence of abraded specimens together with teeth, scales and spines with few little breaks or even no kinds of abrasion, are interpreted as deposits laid down under episodic events of storms (Chahud & Petri, 2015bChahud, A. & Petri, S. (2015b). Geology and Taphonomy from the Base of the Taquaral Member, Irati Formation (Permian, Paraná Basin), Brazil. Acta Geologica Polonica, 65(3): 379-387. https://doi.org/10.1515/agp-2015-0017 ).

The crustaceans of the silty-shale facies are complete or almost complete with scarce examples of little abrasion or broke. The vertebrates are disarticulated, represented mainly by well preserved scales of Sarcopterygii and Palaeonisciformes (Chahud, 2017Chahud, A. (2017). Additional contributions to the knowledge of the Taquaral Member, Irati Formation (Lower Permian, Paraná Basin): Taphonomy and paleoenvironmental implications. Carnets de Geologie, 17: 243-250. https://doi.org/10.4267/2042/64291 ).

The Taquaral Member bivalves were taphonomically studied by Matos et al. (2017)Matos, S.A.; Warren, L.V.; Varejão, F.G.; Assine, M.L. & Simões, M.G. (2017). Permian endemic bivalves of the “Irati anoxic event”, Paraná Basin, Brazil: Taphonomical, paleogeographical and evolutionary implications. Palaeogeography, Palaeoclimatology, Palaeoecology, 469: 18-33. https://doi.org/10.1016/j.palaeo.2016.12.043 who noticed a preferential orientation in a unimodal or bimodal arrangement, characterizing shallow water transport to more distant regions through episodic events of storms.

Paleoenvironmental Considerations

⌅

The Irati stratigraphy is heterogeneous, with geographical differences. It is important therefore, to analyze local sections which clarify different paleoenvironments, along the time.

The overall details of the Taquaral basal deposits allow interpretation of a transgressive tract system (Hachiro, 1991Hachiro, J. (1991). Litotipos, associaçoes faciológicas e sistemas deposicionais da Formação Irati no estado de São Paulo. Master Dissertation. Instituto de Geociências, USP, 175 pp., 1996Hachiro, J. (1996). O Subgrupo Irati (Neopermiano) da Bacia do Paraná. PhD Thesis. São Paulo: Instituto de Geociências-USP, 196 pp.; Assine et al., 2003Assine, M.L.; Zacharias, A.A. & Perinotto, J.A.J. (2003). Paleocorrentes, paleogeografia e seqüências deposicionais da Formação Tatuí, centro-leste do Estado de São Paulo. Revista Brasileira de Geociências, 33(1): 33-40. https://doi.org/10.25249/0375-7536.20033313340 ; Holz et al. 2010Holz, M.; França, A.B.; Souza, P.A.; Lannuzzi, R. & Rohn, R. (2010). A stratigraphic chart of the Late Carboniferous/Permian succession of the eastern border of the Paraná Basin, Brazil, South America. Journal of South American Earth Sciences, 29: 381-399. https://doi.org/10.1016/j.jsames.2009.04.004 ).

According to Holz et al. (2010)Holz, M.; França, A.B.; Souza, P.A.; Lannuzzi, R. & Rohn, R. (2010). A stratigraphic chart of the Late Carboniferous/Permian succession of the eastern border of the Paraná Basin, Brazil, South America. Journal of South American Earth Sciences, 29: 381-399. https://doi.org/10.1016/j.jsames.2009.04.004 , the Taquaral Member was laid down in a shallow environment with very restricted connection with the open ocean. However Chahud & Petri (2013aChahud, A. & Petri, S. (2013a). Paleontology of Taquaral Member silty shale in the State of São Paulo. Brazilian Journal of Geology, 43: 117-123. https://doi.org/10.5327/Z2317-48892013000100010 , 2013bChahud, A. & Petri, S. (2013b). The silty shale Taquaral Member of the early Permian Irati Formation (Paraná Basin, Brazil). Paleontology and paleoenvironments. Swiss Journal of Palaeontology, 132: 119-128. https://doi.org/10.1007/s13358-013-0055-1 , 2014)Chahud, A. & Petri, S. (2014). New chondrichthyans from the Irati Formation (Early Permian, Paraná Basin), Brazil: origin, palaeoenvironmental and palaeogeographical considerations. Proceedings of the Geologists Association, 125: 437-445. https://doi.org/10.1016/j.pgeola.2014.07.006 questioned this connection due to the absence of exclusively marine fossils based on comparison with the current Black Sea system, where typical freshwater animals were replaced by a marine fauna after a connection with the Mediterranean Sea, during a few thousand years (Sorokin & Kuprin, 2007Sorokin, V.M. & Kuprin, P.N. (2007). On the character of Black Sea level rise during the Holocene. Moscow University Geology Bulletin, 62(5): 334-341. https://doi.org/10.3103/S0145875207050055 ).

The silty-shale facies exhibits preserved complete crustaceans and fragile Actinistia scales (Chahud & Petri, 2013aChahud, A. & Petri, S. (2013a). Paleontology of Taquaral Member silty shale in the State of São Paulo. Brazilian Journal of Geology, 43: 117-123. https://doi.org/10.5327/Z2317-48892013000100010 , 2013bChahud, A. & Petri, S. (2013b). The silty shale Taquaral Member of the early Permian Irati Formation (Paraná Basin, Brazil). Paleontology and paleoenvironments. Swiss Journal of Palaeontology, 132: 119-128. https://doi.org/10.1007/s13358-013-0055-1 ), attesting good conditions of preservation. However, no exclusively marine fossil are present, in spite of a long history of Taquaral researches.

The sandy facies, located at the base of the Taquaral Member, is the only evidence of connection with an outside basin. According to Chahud & Petri (2014)Chahud, A. & Petri, S. (2014). New chondrichthyans from the Irati Formation (Early Permian, Paraná Basin), Brazil: origin, palaeoenvironmental and palaeogeographical considerations. Proceedings of the Geologists Association, 125: 437-445. https://doi.org/10.1016/j.pgeola.2014.07.006 the Taquaral waterbody might be connected with the Parnaiba Basin, Pedra de Fogo Formation, northeastern Brazil, during the Permian, for a short time, which might have helped to increase the level of the Taquaral waterbody in the Paraná Basin. The Chondrichthyes Itapyrodus punctatus and Taquaralodus albuquerquei present in both basins, are evidence for this connection (Silva Santos, 1946Silva Santos, R. (1946). Duas novas formas de elasmobranquios do Paleozóico do Meio Norte do Brasil. Anais da Academia Brasileira de Ciências, 18(4): 281-285., 1990Silva Santos, R. (1990). Paleoictiofáunula da Formação Pedra do Fogo, Nordeste do Brasil: Holocephali-Petalodontidae. Anais da Academia Brasileira de Ciências, (62)4: 347-355.; Chahud et al., 2010bChahud, A.; Fairchild, T.R. & Petri, S. (2010b). Chondrichthyans from the base of the Irati Formation Permian, Parana Basin), São Paulo, Brazil. Gondwana Research, 18: 528-537. https://doi.org/10.1016/j.gr.2010.01.006 ; Chahud & Petri, 2010cChahud, A. & Petri, S. (2010c). O tubarão Taquaralodus albuquerquei (Silva Santos, 1946) do Membro Taquaral (Permiano, Formação Irati) no Estado de São Paulo. Acta Biologica Paranaense, 39: 1-17. https://doi.org/10.5380/abpr.v39i0.20236 , 2014Chahud, A. & Petri, S. (2014). New chondrichthyans from the Irati Formation (Early Permian, Paraná Basin), Brazil: origin, palaeoenvironmental and palaeogeographical considerations. Proceedings of the Geologists Association, 125: 437-445. https://doi.org/10.1016/j.pgeola.2014.07.006 ). The absence of these fishes in any other basins suggest that they did not migrate from other territories.

Itapyrodus punctatus is reported, in Paraná Basin, only in the Taquaral sandy facies and only in the State of São Paulo and Parnaiba Basin, as seen above. Other species of Itapyrodus, as yet not named, was also reported only in the State of São Paulo, but in the Corumbataí Formation, younger than Irati (Chahud & Petri, 2016Chahud, A. & Petri, S. (2016). Paleontologia da fácies arenosa do Membro Taquaral (Permiano) no Estado de São Paulo: estado da arte e contribuições adicionais. Geologia USP. Série Científica, 16(3): 105-115. https://doi.org/10.11606/issn.2316-9095.v16i3p105-115 ).

The Taquaralodus albuquerquei also is known only in the Taquaral sandy facies of the State of São Paulo, without any similar fossils, being later replaced by Xenacanthidae of the genera Xenacanthus and Triodus in more recent units, Corumbataí, Teresina and Rio do Rasto formations (Würdig-Maciel, 1975Würdig-Maciel, N.L. (1975). Ichtiodontes e ichtiodorulitos (Pisces) da Formação Estrada Nova e sua aplicação na estratigrafia do Grupo Passa Dois. Pesquisas, 5: 7-165. https://doi.org/10.22456/1807-9806.21830 ; Ragonha, 1984Ragonha, E.W. (1984). Taxionomia de dentes e espinhos isolados de Xenacanthodii (Chondrichthyes, Elasmobranchii) da Formação Corumbataí. Considerações cronológicas e paleoambientais. PhD Thesis. IGc-USP. São Paulo. Brazil.; Pauliv et al., 2014Pauliv, V.E.; Dias, E.V.; Sedor, F.A. & Ribeiro, A.M. (2014). A new Xenacanthiformes shark (Chondrichthyes, Elasmobranchii) from the Late Paleozoic Rio do Rasto Formation (Paraná Basin), Southern Brazil. Anais da Academia Brasileira de Ciências, 86: 135-145. https://doi.org/10.1590/0001-37652014107612 ; 2017Pauliv, V.E.; Martinelli, A.G.; Francischini, H.; Dentzien-Dias, P.; Soares, M.B.; Schultz, C.L. & Ribeiro, A.M. (2017). The first Western Gondwanan species of Triodus Jordan 1849: A new Xenacanthiformes (Chondrichthyes) from the late Paleozoic of Southern Brazil. Journal of South American Earth Sciences, 80: 482-493. https://doi.org/10.1016/j.jsames.2017.09.007 ).

The sudden disappearance of the Chondrichthyes in the Taquaral Member after the sandy facies, possibly was a result of decreasing salinity of water body after the sandy facies deposits, isolated forever from the Parnaíba Basin and, eventually, from the open ocean.

After the beds bearing Itapyrodus punctatus and Taquaralodus albuquerquei in the Pedra de Fogo Formation, Parnaíba Basin turned over to a continental paleoenvironment bearing plant fossils and tetrapods (Cisneros et al., 2015Cisneros, J.C.; Marsicano, C.; Angielczyk, K.D.; Smith, R.M.H.; Richter, M.; Fröbisch, J.; Kammerer C.F. & Sadleir R.W. 2015. New Permian fauna from tropical Gondwana. Nature Communications, 6: 1-8. https://doi.org/10.1038/ncomms9676 ; Conceição et al., 2016Conceição, D.M.; de Andrade, L.S.; Cisneros, J.C.; Iannuzzi, R.; Pereira, A.A. & Machado, F.C. (2016). New petrified forest in Maranhão, Permian (Cisuralian) of the Parnaíba Basin, Brazil. Journal of South American Earth Sciences, 70: 308-323. https://doi.org/10.1016/j.jsames.2016.05.015 ).

The influence of rivers leading to freshwater environments for the Taquaral Member was first suggested by Mussa et al. (1980)Mussa, D.; Carvalho, R.G. & Santos, P.R. (1980). Estudo estratigráfico e Paleoecológico em Ocorrências Fossilíferas da Formação Irati, Estado de São Paulo, Brasil. Boletim do IG/USP, 11: 31-189. https://doi.org/10.11606/issn.2316-8978.v11i0p142-149 based on the presence of Clarkecaris, which, as Anaspidacea, has been associated with freshwater. However, as discussed earlier, Clarkecaris is a transitional form between the present freshwater Anaspidaceae and the Carboniferous Palaeocaridaceae of marine origin or of variable salinity, so it is not a good indicator.

Although no fossils in Taquaral is exclusively freshwater, on the other hand, no ocean fossils are present. Besides, freshwater flows were recognized by the presence of pollen, spores and algae Botryococcus (Lages, 2004Lages, L.C. 2004. A Formação Irati (Grupo Passa Dois, Permiano, Bacia do Paraná) no furo de sondagem FP-01-PR (Sapopema, PR). Master Dissertation. Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Rio Claro, Brazil, 117 pp.).

Carbonate layers bearing bivalve coquinas (Facies 3, Fig. 2) are solely as yet present in the state of Paraná (Matos et al., 2017Matos, S.A.; Warren, L.V.; Varejão, F.G.; Assine, M.L. & Simões, M.G. (2017). Permian endemic bivalves of the “Irati anoxic event”, Paraná Basin, Brazil: Taphonomical, paleogeographical and evolutionary implications. Palaeogeography, Palaeoclimatology, Palaeoecology, 469: 18-33. https://doi.org/10.1016/j.palaeo.2016.12.043 ). They interfinger with the facies silty shale.

During the carbonate layers deposition, the waterbody keep decreasing, caused by the dry climate, resulting a low energy paleoenvironment and the beginning of Assistência Member, anoxic phase (Matos et al., 2017Matos, S.A.; Warren, L.V.; Varejão, F.G.; Assine, M.L. & Simões, M.G. (2017). Permian endemic bivalves of the “Irati anoxic event”, Paraná Basin, Brazil: Taphonomical, paleogeographical and evolutionary implications. Palaeogeography, Palaeoclimatology, Palaeoecology, 469: 18-33. https://doi.org/10.1016/j.palaeo.2016.12.043 ).

Episodic events, such as storms, have always been common during the deposition of the Irati Formation. According to Chahud & Petri (2015a)Chahud, A. & Petri, S. (2015a). Geologia e Paleontologia da Formação Irati (Eopermiano, Bacia do Paraná) no Rio Passa Cinco, Estado de São Paulo. Brazilian Geographical Journal: Geosciences and Humanities research medium, 6(1): 110-120. and Matos et al. (2017)Matos, S.A.; Warren, L.V.; Varejão, F.G.; Assine, M.L. & Simões, M.G. (2017). Permian endemic bivalves of the “Irati anoxic event”, Paraná Basin, Brazil: Taphonomical, paleogeographical and evolutionary implications. Palaeogeography, Palaeoclimatology, Palaeoecology, 469: 18-33. https://doi.org/10.1016/j.palaeo.2016.12.043 , the storms were responsible for the fish and bivalves deposits.

Many fossils occur in paleoenvironments of variable salinity such as acritarchs, bivalves and fishes. Related species are known in older units, Palermo and Tatuí formations and Itararé Group (Silva Santos, 1946Silva Santos, R. (1946). Duas novas formas de elasmobranquios do Paleozóico do Meio Norte do Brasil. Anais da Academia Brasileira de Ciências, 18(4): 281-285.; Fúlfaro et al. 1984Fúlfaro, V.J.; Stevaux, J.C.; Souza-Filho, E.E. & Barcelos, J.H. (1984). A Formação Tatuí (P) no Estado de São Paulo. XXIII Congresso Brasileiro de Geologia. Rio de Janeiro, Sociedade Brasileira de Geologia. Anais., 2: 711-723.; Cazzulo-Klepzig et al. 1989Cazzulo-Klepzig, M.; Piccoli, A.E.M. & Marques-Toigo, M. (1989). Reconhecimento de um marco estratigráfico com significado paleoecológico no Permiano da Bacia do Paraná (Grupos Guatá e Passa Dois). XI Congresso Brasileiro De Paleontologia, Curitiba. Anais, 2: 971-982.; Marasco et al. 1993Marasco, S.A.; Souza, P.A. & Pires, F.A. (1993). Ocorrência de paleomicroplâncton marinho (Acritarcha) associado a ictiofósseis na base do Membro Taquaral, Formação Iratí (Permiano Superior da bacia do Paraná), região de Itapetininga, Estado de São Paulo. XIII Congresso Brasileiro de Paleontologia e I Simpósio Paleontológico do Cone Sul, São Leopoldo.; Holz et al. 1998Holz, M.; Zwetsch, G.; Simões, M.G. & Carlucci, R. (1998). Tafonomia dos invertebrados na Formação Palermo (Kunguriano) da Bacia do Paraná no Rio Grande do Sul: Lingulídeos desarticulados em fácies de tempestitos. XL Congresso Brasileiro de Geologia, Belo Horizonte, 453.; Chahud & Petri, 2015bChahud, A. & Petri, S. (2015b). Geology and Taphonomy from the Base of the Taquaral Member, Irati Formation (Permian, Paraná Basin), Brazil. Acta Geologica Polonica, 65(3): 379-387. https://doi.org/10.1515/agp-2015-0017 ; 2015cChahud, A. & Petri, S. (2015c). The Tatuí Formation (Early Permian, Paraná Basin), Brazil: Paleontology and Paleoenvironmental Considerations. Earth Sciences Research Journal, 19(2): 153-158. https://doi.org/10.15446/esrj.v19n2.50245 ). Many species may have survived paleoenvironmental changes, reaching younger units due to their adaptability (Chahud & Petri, 2016Chahud, A. & Petri, S. (2016). Paleontologia da fácies arenosa do Membro Taquaral (Permiano) no Estado de São Paulo: estado da arte e contribuições adicionais. Geologia USP. Série Científica, 16(3): 105-115. https://doi.org/10.11606/issn.2316-9095.v16i3p105-115 , Matos et al., 2017Matos, S.A.; Warren, L.V.; Varejão, F.G.; Assine, M.L. & Simões, M.G. (2017). Permian endemic bivalves of the “Irati anoxic event”, Paraná Basin, Brazil: Taphonomical, paleogeographical and evolutionary implications. Palaeogeography, Palaeoclimatology, Palaeoecology, 469: 18-33. https://doi.org/10.1016/j.palaeo.2016.12.043 ). These species were restricted to specific conditions of the basin, allowing survival, in restricted or epicontinental seas, like Baltic, Caspian and Aral (Zenkevich, 1957Zenkevich, L.A. (1957). Caspian and Aral Seas. Geological Society of American Memoir, 67: 891-916. https://doi.org/10.1130/MEM67V1-p891 ; Brenner, 2005Brenner, W.W. (2005). Holocene environmental history of the Gotland Basin (Baltic Sea) a micropalaeontological model. Palaeogeography, Palaeoclimatology, Palaeoecology, 220: 227-241. https://doi.org/10.1016/j.palaeo.2004.12.010 ).

Conclusions

⌅

The Taquaral Member, the basal unit of the Irati Formation, is composed mainly of non-bituminous silty-shales, with sandy layers located at the base, near the border of the basin and thin carbonates layers in the upper half, of the thickest stratigraphic sections.

The microfossils include several genera of palynomorphs, spores, pollen, acritarchs and the Botryococcus algae. None were found to be reliable indicators of oceanic, freshwater, or continental environments for their adaptability for changing or ease of transportation.

The lowermost Taquaral sandy-facies, in spite of thin (ten to forty centimeters, seldom 1 meter) is noteworthy for testifying an unique happening a connection between two basins, Paraná and Parnaíba.

Other noteworthy characteristic of the sandy-facies as the great diversity and frequency of fishes and the presence of both Taquaral Member and Pedra de Fogo Formation, of the species Itapyrodus punctatus and Taquaralodus albuquerquei. These species occur only in these two units, absent in any other basin in Brazil and abroad, evidence of the connection between two basins as mentioned above. Several groups of fishes still upholder the lower salinity but others were extinct, like the genus Taquaralodus.

The better preserved fossils are the crustaceans from the silty shale facies. The Clarkecaris crustacean is the most common, endemic, different from all existing Anaspidacea, its evolution in isolation resulted in an unique form, no descendants in the geological record.