Paraná Basin

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Figure 1. Geological Map of the Paraná Basin.[1]

According to Milani et al,[2] the Paraná Basin is a large sedimentary region of South America, which includes territorial portions of southern Brazil, eastern Paraguay, northeastern Argentina and northern Uruguay, totaling an area which is close to 1.5 million square kilometers (Figure 1). The basin has an oval shape with the major axis N-S, its current boundary is defined by erosive limits related largely to the Mesozoic-Cenozoic tectonic history of the continent. Numerous researchers have been involved in the investigation of this basin, some of these works were of particular relevance as a regional summaries, highlighting the White report[3], the works of Sanford and Lange,[4] Northfleet et al.,[5], Schneider et al.[6], Smith et al. (1978), Adams (1980), Fulfaro et al.[7] and Zalán et al.[8].

Sediments were deposited in the Paraná Basin during the Paleozoic and the Mesozoic Era (450-65 Ma), keeping record of nearly 400 million years of Phanerozoic history of this region of the world. The basin accumulated siliciclastic, chemical and volcaniclastic sediments, between the Neo-Ordovician and Late Cretaceous. Part of the accumulation time a was interspersed with depositional gaps that separate the various supersequences.

Evolutionary Synthesis[edit]

The integrated analysis of basin subsidence shows a relationship between the cycles of depositional space creation in intracratonic areas and orogenic episodes. Several orogenic periods and compressive deformation pulses in the active margin of Gondwana were the major controls of accommodation space variation rates. The orogenic apex matches periods of accelerated development of the interior syneclises, and in the absence of orogenic climax records tectonic uplift on a continental scale in the Paraná Basin. As a result, the temporal amplitude of Paraná Basin supersequences are clearly confined by the temporal limits of the different subsidence cycles controlled by Paleozoic orogenies on the Gondwanan margin. Sea level, climate and sediment supply had supporting roles in transgressive-regressive marine cycles, since their deposits do not match the global eustatic oscillations (Sloss, 1990).

The tectonic-stratigraphic evolution of the Paraná Basin developed in the Gondwanan cratonic interior, which had a convergent relationship with the oceanic lithosphere of Panthalassa (Gondwanides Orogenic Cycle), during the Phanerozoic. This orogenic cycle is marked by two main collisional cycles: Famatinian (Ordovician to Devonian) and Gondwanic (Carboniferous to Triassic; Ramos[9] 1990). The structure of the Paraná Basin developed in northeast–southwest elongated depressions, according to the plot of the Precambrian substrate.[10] The basement weakness zones being reactivated under the compressional field, which originated on the continent's edge by the Ocloyic Orogeny (Famatinian),[11] which provided accommodation space for the of the first unit: the Rio Ivaí supersequence.

When regional flexural subsidence resumed, Paraná and Gondwana I Supersequences had accumulated sediments, with the boundary between them marked by a gap of 70 Ma, a gap in the tectonic-sedimentary basin history. The Gondwanic orogenic cycle followed the Famatinian orogenic cycle, creating an extensive mountain belt southwest of the Paraná Basin, which overloaded the continental lithosphere. This was propagated by lithospheric flexure in Gondwana, leading to subsidence in the basin by tectonic adjustment mechanisms and thus initiating the interior synclines phase.[11][8]; Sign 1996; [10][12]).

The start of Carboniferous sedimentation occurred at a time of major changes, both tectonic and climatic. The package that happens to be the neo-Devonian discordance, the Gondwana I super sequence,[10] demonstrates a complete transgressive-regressive cycle; the result of the invasion and subsequent exit of the Panthalassa Sea into Gondwana. The accumulation of the Gondwana I supersequence was accompanied by a gradual closing of the Paraná Basin, restricting marine incursions from the west. The character of an intracratonic basin was then gradually assumed, and the basin became trapped in the arid interior of the continental Mesozoic Gondwana.

The arrival of the Triassic saw a widespread strain in the southern portion of paleocontinent Gondwana.[13] The Gondwana II supersequence of the Paraná Basin, restricted to occurrences in Rio Grande do Sul and the Uruguayan portions of the basin, is part of this regional context and seems to represent a sedimentation accumulation in graben type basins.

In the Early Cretaceous, the Earth's crust underwent to a colossal splitting, associated with basaltic magmatism ratios without compare in the planets history. This event caused the breakup of the Gondwanan supercontinent and began the evolution of the South Atlantic Ocean. The Serra Geral magmatism marked the end of extensive sedimentation events in the supercontinent´s interior. After the opening of the Atlantic Ocean, the South American Platform maintained its widespread ascensional character - started at the time of Botucatu sedimentation - until the buildup of almost 2,000 m thickness of basaltic lavas. When the volcanic activities ceased, there were some isostatic adjustments and established of a depression on the basaltic package where, in the Late Cretaceous, would later build the last supersequence (Bauru Supersequence) in the area occupied by the Paraná Basin.

Stratigraphic Record[edit]

The stratigraphic record of the Paraná Basin comprises a sedimentary-magmatic package with a maximum total thickness of c.7000 meters. Milani[10] divided this record into six large scale units or supersequences,[14] in the form of rock packages representing each temporal interval with tens of millions of years of duration and enveloped by surfaces of discordance of interregional character. These are the Rio Ivaí, Paraná, Gondwana I, Gondwana II, Gondwana III and Bauru.

Rio Ivaí Supersequence[edit]

This unit, the oldest identified in the Paraná Basin, rests directly on the various areas of the basement. Its top is marked by a regional unconformity surface that juxtaposes the lower Silurian strata of the upper Rio Group Ivaí when it displays its complete record into the Lower Devonian, at the base of the Furnas Formation.

Three units constitute the Rio Ivaí Group: Alto das Garças, Iapó and Vila Maria Formations.[15]. The Alto das Garças Formation, with a maximum thickness of 300 meters, is essentially sand dominated and may include a basal quartzes conglomerate, passing to conglomeratic sandstones with cross stratification. The upper portion of the unit is represented by an increase in the amount of silt and clay and reddish coloration.

The Iapó Formation consists of diamictites of different colors, with silty-sandy matrix and varied nature of clasts. The Vila Maria Formation is comprised of fossiliferous pelites representing the most important stratigraphic mark of all Supersequence Rio Ivaí. Are generally red colored, micaceous and ferruginous appearance, but locally dark gray and quite fossiliferous. In turn, the sandstones and siltstones of the upper portion display hummocky cross-bedding and contraction desiccation cracks.

The succession of facies in the Rio Ivaí Supersequence documents the first transgressive-regressive cycle of cratonic sedimentation of the Paraná Basin. The nature of sedimentation is dominantly marine, with the transgressive portion extending from the base unit to the level of pelites of the Vila Maria Formation, which manifest the maximum flood of this sedimentary cycle. Then to top it develops the regressive portion, which has limited preservation due to the pronounced erosive nature of the "pre-Furnas"discordance. In Paraguay, the regressive portion is well preserved, corresponding to the fine, micaceous sandstones and fossiliferous of the Cariy Formation.

Paraná Supersequence[edit]

The Devonian package of the basin, the Paraná Group, has a maximum thickness of 800 meters and overlies the Ordovician-Silurian strata of the Rio Ivaí Group, but also can be found directly on basement rocks.

Two units constitute the Paraná Group: Furnas and Ponta Grossa Formations. The Furnas Formation is represented by a succession of white quartz sandstones, medium to coarse, with high kaolinite content and displaying cross stratification of various kinds. Near the base, are frequent conglomeratic beds up to 1 m thick. In its middle portion, dominated by sandstones of medium grain size, intercalated with thinner siltstone and muscovite rich shale, emphasizing the laminated aspect of that interval. Herringbone cross-stratification also occurs.[15] At the top, medium to coarse sandstones come to dominate, but also occur in very thin layers of sandstone with hummocky stratification type. Continuous increase in mudstone interbeds towards the top shows a gradational transition to the Ponta Grossa Formation.

The Ponta Grossa Formation is represented in the lower portion, by shales c.100 meters thick, containing fine sandstone lenses with stratifications reworked by waves, and black laminated carbonaceous shale, which is an important marker for stratigraphic correlation in the subsurface and a potential generator of hydrocarbons throughout its range in the central area of the Paraná Basin. The middle portion, sandstone and siltstone alternations reflect a progradation of deltaic systems. The upper portion, predominantly mudstone, documents renewed flooding on a large scale, which caps this unit.

The supersequence Paraná is the second transgressive-regressive cycle of the stratigraphic record of the Paraná Basin. Marine drowning in the Paraná Basin persisted until at least the Frasnian, but not with the magnitude and the anoxic development then observed in the Paleozoic basins of northern Brazil.

Gondwana I Supersequence[edit]

The Gondwana I Supersequence[10] encompasses the largest sedimentary volume of the Paraná Basin, emerging in an almost continuous belt and displaying, in the subsurface, a maximum total thickness of c.2500 meters. This unit reflects a wide variety of depositional systems, succeeding in time and evolving between sedimentation with glacial influences to a large, arid continental interior dominated by aeolian dune fields.

Six units constitute the Gondwana I Supersequence: Itararé Group, Aquidauana Formation, Guatá Group, Passa Dois Group and Pirambóia and Sanga of the Cabral Formations. The lower portion of Gondwana Supersequence I is represented by deposits related to a phase of deglaciation of the Mississippian glaciers, represented by the Itararé Group and Aquidauana Formation.

The deglaciation brought as a direct consequence a rise in relative sea level, identified as the "Permian transgression" by Lavina and Lopes[16]. From this transgressive trend, glaciogenic strata are succeeded by the sedimentary strata of Guatá Group, with common reworking of deltaic lobes by tides.

Passa Dois Group sedimentation developed following a final regressive trend on a large scale. Continental systems came to dominate the basin, representing the silting of the remaining accommodation space, whilst sedimentary structures linked to the action of tides gave way to a progradational complex of red beds including deltaic lobes lacustrine mudstones, aeolian and fluvial deposits.[17]

The Sanga of the Cabral Formation in the south and Pirambóia Formation in the north represent the advance of the continental systems on lake remnants of the "Passa Dois Basin". These formations are represented fluvial and aeolian deposits composing a wedge that thins to the southwest of the basin.

In brief, the Gondwana I supersequence documents a complete transgressive-regressive cycle, which begins at the base of Pennsylvanian glacial package reaches maximum marine drowning conditions in Artinskian and closes on continental deposits at the beginning of the Mesozoic.

Gondwana II Supersequence[edit]

The establishment of the Triassic System in the Paraná Basin presents a link to the fossil rich package of the Santa Maria Formation, which occurs in the southern portion of the basin.

In subsurface data, it is observed that mudstone deposits abruptly overlap the previous sandy unit. This abrupt contact, reflects a rapid "transgression lake" on the unconformity surface which marks the top of supersequence Gondwana I, it could be indicative of a rapid episode of subsidence of the substrate and development of a starved basin. The subsequent mudstone fill and sandstones progradation is covered by a sharp contact by sandstones of the Tacuarembó Formation in Uruguay and by the Botucatu Formation in Southern Brazil.

Thus, the Gondwana II Supersequence attribute set allows an interpretation that the subsidence of the Paraná Basin could be related to the development of asymmetric extensional grabens, settling the river drainage on the flexural ramp of this system. The cyclicality observed in this package, switching between lacustrine mudstones and fluvial sandstones, would have developed in response to changes in the lake base level due to a matched control of tectonics and climate (Milani et al. 1998)[12].

Gondwana III Supersequence[edit]

This supersequence is amply distributed in the Paraná Basin and it is most represented by the aeolian sediments of the Botucatu Formation and magmatic rocks of Serra Geral Formation.

The Botucatu Formation cover an exceptionally large area, in excess of 1,300,000 square kilometers, representing one of the most extensive occurrences of continental sediments in the world. The Parana Basin experienced widespread desertification, which occurred throughout the Gondwanan Supercontinent, during the Mesozoic pre-breakup times. Correlative deposits are also found in Africa, and constitute the upper portion of Karoo System. Towards the top of the unit the sandstones are intercalated with the first lava flows that marked the initial stages of Gondwana's breakup.

The Serra Geral Formation represents an igneous event that culminated with a huge pile of lavas. A package of volcanic rocks up to 2,000 meters thick overlies the sediments of Paraná Basin, which were intruded by a network of dikes and sills. During this event, in Early Cretaceous time, the continental crust of the Paraná Basin experienced a very active rifting process and the basin itself underwent the most intense structural rearrangement of its history.

Bauru Supersequence[edit]

Bauru Supersequence corresponds lithostratigraphically to the Caiuá and Bauru Groups. It represents a continental post-lava cover strata and it is constituted by a siliciclastic unit, (sandy-conglomeratic deposits, including clasts of various lithologies, such as volcanics, sandstones, shales and basement crystalline rocks), accumulated in semi arid to desert conditions. This sequence was accommodated in the flexural depression originated by the load of the basalt pile. This was the last significant episode of subsidence in the Paraná Basin. The accumulation of Bauru Supersequence took place during Aptian to Maastrichtian time and it has c.300 m of thickness over 370.000 km².

The Caiaú Group corresponds to the aeolian system of the Caiuá Desert and it is compound by the Uberaba, Vale do Rio do Peixe, Araçatuba, São José do Rio Preto, Presidente Prudente and Marília formations.

The Bauru Group corresponds to systems tracts deposits of a semi-arid environment formed by alluvial fans. Sand sheet deposits were crossed by ephemeral fluvial systems which supplied the Caiuá desert. This Group comprises the Rio Paraná, Goio Erê and Santo Anastácio formations.

Paleontological Setting[edit]

The Paraná Basin has famous paleontological representatives, such as specimens of the Mesosaurus fauna and Glossopteris flora, both found respectively in Rio Bonito and Irati formations, which played an important role in the institution of the continental drift theory proposed in the last century. Recently there have been great repercussions in the paleontological studies of vertebrates in the Triassic formations of Santa Maria and Caturrita (including reptiles, dicynodonts, cynodonts and primitive dinosaur forms) and dinosaurs and other reptiles of the Bauru Cretaceous sequence.

The Guarani Aquifer[edit]

Figure 2 The Guarani Aquifer location.

The Guarani Aquifer is located in the Paraná Basin in South America (Center-Southwest of Brazil, Northeast of Argentina, Northwest of Uruguay and Southeast of Paraguay) (Figure 2). It is a mixed type of aquifer, porous and fractured, covering 1,200,000 km2.

Deposition of the sandstone portions made the existence of the aquifer possible. The two sandstones units are the Piramboia Formation at the bottom and, most important, the Botucatu Formation at the top. During the Jurassic period a desert environment prevailed in this area, similar to the Sahara Desert today, depositing medium grained, well sorted, quartzose sandstones, red and rose in color.

In the Cretaceous, when the break up of Pangaea reached South America and South Africa a huge amount of lava flowed through the fissures and cracks, creating a impermeable thick basalt cover. Later, cycles of glaciation and deglaciation created fissures and cracks in this basalt cover allowing water from ice melting and precipitation to infiltrate and, thus, form the aquifer. The water has first to infiltrate the basalt through the fractures and through the porous until it percolates into the sandstones.

Some hydrogeologic characteristics:[18]

  • A system with unconfined and confined parts
  • Thickness 50–800 m, average 250 m
  • Effective porosity 0.15–0.3
  • Recharge 166 km3/year – PRECIPITATION
  • Hydraulic conductivity 8.7-13 m/day

References[edit]

  1. ↑ Milani, E. J., 2004, Comentários sobre a origem e evolução tectônica da Bacia do Paraná, in V. Mantesso-Neto, A. Bartorelli, C. D. R. Carneiro, and B. B. Brito-Neves, eds., Geologia do Continente Sul-Americano: Evolução da Obra de Fernando Flávio Marques de Almeida: São Paulo, Brazil, Editora Beca, p. 265–279.
  2. ↑ 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.
  3. ↑ White, I. C., 1908, Relatório sobre as coal measures e rochas associadas ao sul do Brasil. Rio de Janeiro: Comissão das Minas de Carvão de Pedra do Brasil, 300 p.
  4. ↑ Sanford, R. M. and F. W. Lange, 1960, Basin-study approach to oil evaluation of Paraná miogeosyncline, south Brazil: AAPG Bulletin, vol. 44, p. 1316-1370
  5. ↑ Northfleet, A. A., R. A. Medeiros, and H. Mühlmann, 1969, Reavaliação dos dados geológicos da Bacia do Paraná. Boletim Técnico da Petrobras, Rio de Janeiro, v.12, n.3, p. 291-346
  6. ↑ Scneider, R. L.; H. Mühlmann, E. Tommasi, R. A. Medeiros, R. F. Daemon, and A. A. Noguierra, 1974, Revisão estratigráfica da Bacia do Paraná. In: Congresso Brasileiro de Geologia, Porto Alegre. Anais do São Paulo: Sociedade Brasileira de Geologia, v. 1, p. 41-65.
  7. ↑ Fulfaro, V. J., E. Gama Junior, and P. C. Soares, 1980. Revisão estratigráfica da Bacia do Paraná. São Paulo: Paulipetro, 167 p.
  8. ↑ 8.0 8.1 Zalán, P. V., S. Wolff, M. A. M. Astolfi, I. S. Vieira, J. C. J. Conceição, V. T. Appi, E. V. Santos Neto, J. R. Cerqueira, and A. Marques, 1990, The Paraná Basin, Brazil, in M. W. Leighton, D. R. Kolata, D. F. Oltz, and J. J. Eidel, eds,. Interior cratonic basins: AAPG Memoir 51, p. 681-708.
  9. ↑ Ramos, V. A., 1988, Tectonics of the late Proterozoic–early Paleozoic: A collisional history of southern South America: Episodes, v. 11, no. 3, p. 168–174.
  10. ↑ 10.0 10.1 10.2 10.3 10.4 Milani, E. J., 1997, Evolução tectono-estratigráfica da Bacia do Paraná e seu relacionamento com a geodinâmica fanerozóica do Gondwana sul-ocidental. 2 v. Tese (Doutorado) - Universidade Federal do Rio Grande do Sul, Porto Alegre
  11. ↑ 11.0 11.1 Ramos, V. A., T. E. Jordan, R. W. Allmendinger, C. Mpodozis, J. M. Kay, J. M. Cortés, and M. Palma, 1986, Paleozoic terranes of the central Argentine-Chilean Andes: Tectonics, v. 5, n0. 6, p. 855–880
  12. ↑ 12.0 12.1 Milani, E. J., U. F. Faccini, C. M. S. Scherer, L. M. Araújo, and J. A. Cupertino, 1998, Sequences and stratigraphic hierarchy of the Paraná Basin (Ordovician to Cretaceous), Southern Brazil: Boletim IG-USP, São Paulo Série Científica, 29 p. 125–173.
  13. ↑ Uliana, M. A. and K. Biddle, 1988, Mesozoic-Cenozoic paleogeographic and geodynamic evolution of southern South America. Revista Brasileira de Geociências, São Paulo, v. 18, p. 172-190
  14. ↑ Vail, P. R., R. M. Mitchum Jr., and S. Thompson III, 1977, Seismic stratigraphy and global changes of sea level: Part 4. Global cycles of relative changes of sea level, in C. E. Payton, ed., Seismic stratigraphy—Applications to hydrocarbon exploration: AAPG Memoir 26, p. 83–97
  15. ↑ 15.0 15.1 Assine, M. L., 1996, Aspectos da estratigrafia das sequências pré-carboníferas da Bacia do Paraná no Brasil. 1996. 207 p. Tese (Doutorado) - Universidade de São Paulo, São Paulo.
  16. ↑ : Lavina, E. L., and R. C. Lopes, 1987, A transgressao marinha do Permiano Inferior e a evoluçao paleogeografica do Super-Grupo Tubarao no Estado do Rio Grande do Sul: Paula Coutiana, v. 1, p. 51–103
  17. ↑ Lavina, E. L., 1988, The Passa Dois Group: Sedimentology, stratigraphy and paleontology of the Gondwana sequence of the Paraná Basin: 7th Interational Gondwana Symposium Excursion Guide Book A2, p. 24–29.
  18. ↑ Betiollo, L. M. , 2006, Caracterização Estrutural, Hidrogeológica E Hidroquímica Dos Sistemas Aquiferos Guarani E Serra Geral No Nordeste Do Rio Grande Do Sul, Brasil: CPRM MEDIA, p. 72

in gauge

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