Itaboraí Formation
Stratigraphic range: Early Eocene (Itaboraian)
~
TypeGeological formation
Sub-unitsSee text
UnderliesEarly Eocene basalt &
Late Eocene to Early Oligocene conglomerates (Rio Frio Formation)
OverliesPrecambrian basement
Area1 km2 (0.39 sq mi)
Thicknessup to 100 m (330 ft)
Lithology
PrimaryLimestone, marl
OtherTravertine, lignite
Location
Coordinates22°06′S 41°36′W / 22.1°S 41.6°W / -22.1; -41.6
Approximate paleocoordinates25°00′S 30°00′W / 25.0°S 30.0°W / -25.0; -30.0
RegionRio de Janeiro
Country Brazil
ExtentItaboraí Basin
Type section
Named forItaboraí
Named byLeinz
Year defined1938
Itaboraí Formation is located in Brazil
Itaboraí Formation
Itaboraí Formation (Brazil)

The Itaboraí Formation (Portuguese: Formação Itaboraí)[1] is a highly fossiliferous geologic formation and Lagerstätte[2] of the Itaboraí Basin in Rio de Janeiro, southeastern Brazil. The formation reaching a thickness of 100 metres (330 ft) is the defining unit for the Itaboraian South American land mammal age (SALMA), dating to the Early Eocene, approximately 53 to 50 Ma.

The formation is restricted to the Itaboraí Basin, a minibasin of 1 square kilometre (0.39 sq mi) around the city of Itaboraí, 34 kilometres (21 mi) northeast of Rio de Janeiro, and comprises limestones, marls and lignites, deposited in an alluvial to lacustrine environment, dominated by heavy rainfall. The formation overlies Precambrian basement and is overlain by Early Eocene basalts and Late Eocene to Early Oligocene conglomerates.

The up to 100 metres (330 ft) thick formation has provided many fossil mammals of various groups among which the marsupials and related metatherians dominate, birds, snakes, crocodiles, amphibians, and several species of gastropods. Several genera and species were named after the formation; the marsupials Itaboraidelphys camposi and Carolopaulacoutoia itaboraiensis, the birds Itaboravis elaphrocnemoides, Eutreptodactylus itaboraiensis and Eutreptodactylus itaboraiensis, the snake Itaboraiophis depressus and the caiman Eocaiman itaboraiensis and the gastropods Itaborahia lamegoi, Biomphalaria itaboraiensis and Gastrocopta itaboraiensis.

The formation is the richest Cenozoic fossiliferous formation of Brazil, leading to the establishment of the Parque Paleontológico de São José de Itaboraí ("São José de Itaboraí Paleontological Park") in 1995. The site is a candidate for becoming a UNESCO World Heritage Site.

Etymology

The word "Itaboraí" is of Tupi origin, and has two possible etymologies:

  • "River of beautiful stones", a combination of the words itá (stone), porã (beautiful) and y (river)[3]
  • "River of brilliant stones", derived from the words itá (stone), berab (brilliant) and y (river)[4]

Description

The Itaboraí Formation is restricted to the Itaboraí Basin, a minibasin stretching across an area of 1 square kilometre (0.39 sq mi) of 1,400 by 500 metres (4,600 ft × 1,600 ft), in the vicinity of Itaboraí 34 kilometres (21 mi) northeast of Rio de Janeiro, southeastern Brazil.[5] Between 1933 and 1984, a local cement company exploited the rocks in the area and their workers discovered the first fossil remains in the formation.[6] The now abandoned and largely inaccessible limestone quarries of this locality have yielded a diverse mammalian fauna from early late Paleocene fissure fillings.[7] The sediments of the formation were described by Leinz in 1938.[8] Presently, the basin is filled up with water impeding any collecting activity.[9]

Basin history

The small basin, a small half-graben, is the oldest[10] and smallest[11] of several Cenozoic rift basins stretching across 1,000 kilometres (620 mi) along a west-southwest to east-northeast trend between the Paraná Basin to the northwest and the Santos Basin to the southeast, separated by the Serra da Mantiqueira and Serra do Mar respectively. This Continental Rift of Southern Brazil (CRSB) comprises the Curitiba, São Paulo, Taubaté, Resende, Volta Redonda, Macacu, Barra de São João and Itaboraí Basins.[12]

An erosional surface, correlated with a 55 Ma sea-level lowstand representing the Paleocene-Eocene transition and associated with magmatism, has been recorded in the various Atlantic marginal basins along the Brazilian coast; Pelotas, Santos, Campos, Espírito Santo, Cumuruxatiba, Jequitinhonha and Mucuri Basins.[13]

Stratigraphy

Map and stratigraphic column of the Itaboraí Basin

The Itaboraí Formation rests unconformably on top of the Precambrian Paraíba do Sul Group, part of the Meso- to Neoproterozoic Paraíba do Sul Complex.[14] The Paleogene succession of the minibasin reaches a thickness of 100 metres (330 ft) and consists of three depositional sequences, with the Itaboraí Formation representing the first two;[15]

  • Sequence 1 (S1) - clastic limestones with travertine, grey carbonates and oolitic limestones, carbonatic shales and lignites, deposited in a lacustrine environment, originating from debris flows in a tectonic lake. From this sequence gastropods are abundant, while woods, reptiles and mammals are scarce.[11]
  • Sequence 2 (S2) - carbonates filling caverns and dissolution cracks on a karstic surface of Sequence 1, comprising fossiliferous marls, deposited in an alluvial to lacustrine environment, transported into these cavities by heavy rains and gravitational flows[11]
  • Sequence 3 (S3) - terrestrial siliciclastic sediments, including mudstones, sandstones and sandy conglomerates of Late Eocene to Early Oligocene age, derived from the surrounding basement gneisses, deposited by mudflows in a subaerial alluvial fan environment. These sediments, referred to as the Rio Frio Formation,[1] have been correlated with the Eocene to Oligocene Resende Formation of the eponymous basin.[13]

The Itaboraí Formation is separated from Sequence 3 by basaltic volcanic rocks, formed in the Early Eocene.[16]

Thin section analysis suggests the travertine sequence went through a series of diagenetic processes: firstly, the deposition of the primary carbonate, followed by a set of percolating iron oxide enriched fluids and lastly a set of silica-rich fluids leading to the silica chalcedony and micro-crystalline deposition.[17]

Age

The formation was deposited during the Early Eocene Climatic Optimum, here indicated as "Eocene hyperthermal"

The Itaboraí Formation, defining the Itaboraian SALMA, was first thought to be early to mid Paleocene in age, until dating performed by Woodburne et al. in 2014 suggested as a more probable early Eocene age (53–50 Ma),[18][19] spanning polarity chron 23.[20] The overlying basalts have been dated to the Early Eocene (52.6 ± 2.4 Ma). Another very important source of data is palynological analysis of a coal-bearing horizon (lignite) interlayered with alluvial fan deposits at the northern border of the Itaboraí Basin, suggesting a Paleocene to Eocene age.[21] During this time, a biogeographical connection existed with Antarctica and, though separated by the developing South Atlantic, with Africa.[22] The deposits of the formation were formed during the Early Eocene Climatic Optimum (EECO), just after the Paleocene-Eocene Thermal Maximum.[23]

Paleontological significance

The xenungulate Carodnia comes from the Itaboraí Formation

The Itaboraí Formation is the richest and one of few formations in Brazil providing Paleogene mammal faunas, between the older Tiupampan Maria Farinha Formation of the Parnaíba Basin and the younger Divisaderan Guabirotuba Formation of the Curitiba Basin, the Tinguirirican Entre-Córregos Formation of the Aiuruoca Basin and the Deseadan Tremembé Formation of the Taubaté Basin.[24]

Despite its relatively small size, the São José de Itaboraí Basin comprises a diversified fossil assemblage. Among the groups found there, fossil birds are very rare, mainly due to their pneumatized bones. Only three bird species have been described up to this moment from the Itaboraí Basin. Diogenornis fragilis, a probable ratite ancestor, stands out for its good preservation and the number of specimens preserved.[25] In the Paleocene of the southern hemisphere, small terrestrial birds have only been discovered in the late Paleocene fissure fillings of the Itaboraí Formation.[7]

The relative fossil diversity of the Itaboraí Formation at family level consists of 44% mammals, 23% mollusks, 14% reptiles (lizards, chelonians, crocodyliforms), 7% birds, 5% amphibians and 7% plants.[26] Fish are one of the few groups not found to date in the lacustrine formation.[27] The formation has provided many marsupials and related metatherians. The species Lamegoia conodonta is the largest "condylarth" at Itaboraí and approximates the size of a wolf. Ricardocifellia protocenica, originally described as Paulacoutoia protocenica, is the smallest of the "condylarth" species of Itaboraí, but the most abundant.[28] The most abundant litoptern found in the formation is Protolipterna ellipsodontoides.[29]

Sequence 1 of the formation has provided many land snails, among which several new species. The records of Itaboraí are the oldest for the genera Austrodiscus, Brachypodella, Bulimulus, Cecilioides, Cyclodontina, Eoborus, Gastrocopta, Leiostracus, Plagiodontes and Temesa. Also, the formation contains the oldest record for the families Orthalicidae, Gastrocoptidae, Ferussaciidae and Strophocheilidae.[30]

Several genera and species were named after the formation; the marsupials Itaboraidelphys camposi and Carolopaulacoutoia itaboraiensis, the birds Itaboravis elaphrocnemoides, Eutreptodactylus itaboraiensis and Eutreptodactylus itaboraiensis, the snake Itaboraiophis depressus and crocodile Eocaiman itaboraiensis and the gastropods Itaborahia lamegoi, Biomphalaria itaboraiensis and Gastrocopta itaboraiensis.

Because of its paleontological importance, the Itaboraí Basin area was designated as a paleontological park in 1995: Parque Paleontológico de São José de Itaboraí ("São José de Itaboraí Paleontological Park").[31] The park was established to preserve the geology and highlight the importance of the paleontological richness of the area.[32]

The formation is named as one of the fossil sites of potential World Heritage Value by the IUCN in 1996.[33]

Fossil content

Fossils recovered from the formation include:[34][35][36][37]

ClassGroupFossilsImagesNotes
MammalsMarsupialsBergqvistherium primigenia[38]
Carolocoutoia ferigoloi[39]
Carolopaulacoutoia itaboraiensis[21]
Derorhynchus singularis[21]
Didelphopsis cabrerai[21][40]
Eobrasilia coutoi[41][40]
Gashternia carioca[21][42]
Gaylordia macrocynodonta[43][40]
Gaylordia mater[44][40]
Guggenheimia brasiliensis[21][40]
Guggenheimia crocheti[21][40]
Itaboraidelphys camposi[40]
Marmosopsis juradoi[21]
Minusculodelphis minimus[45][40]
Minusculodelphis modicum[45][40]
Mirandatherium alipioi[21][40]
Monodelphopsis travassosi[21][46]
Periprotodidelphis bergqvistae[47]
Protodidelphis mastodontoides[48]
Protodidelphis vanzolinii[49]
Riolestes capricornicus[50]
Xenodelphis doelloi[36]
Australidelphia indet., Didelphidae indet., Didolodontidae indet., Microbiotheriidae indet., Paucituberculata indet., Pediomyidae indet., Protodidelphidae indet.[51][52]
HatcheriformesZeusdelphys complicatus[53][40]
MetatheriaAustropediomys marshalli[54]
Herpetotheriidae indet.[36]
Peradectidae indet.[51]
ArmadillosRiostegotherium yanei[55][56]
AstrapotheresTetragonostylops apthomasi[57]
DidolodontidaeLamegoia conodonta[58][59]
Ricardocifellia protocenica
syn. Paulacoutoia protocenica		[60][61]
LitopternsAsmithwoodwardia scotti[21]
Miguelsoria parayirunhor[62]
Paranisolambda prodromus[63]
Protolipterna ellipsodontoides[64]
Victorlemoinea prototypica[21][65]
NotoungulataCamargomendesia pristina[21]
Colbertia magellanica[21]
Homalostylops atavus[66]
Henricosbornia sp.[21]
Notoungulata indet.[36]
SparassodontsPalaeocladosictis mosesi[36]
Patene simpsoni[50]
?Arminiheringia sp.[36]
Hathlyacininae indet.[51]
Borhyaenidae indet.[51]
PolydolopimorphiaBobbschaefferia fluminensis[21][40]
Epidolops ameghinoi[21][67]
Polydolopidae indet.[51][52]
SimpsonitheriaProcaroloameghinia pricei[21][40]
XenungulataCarodnia vieirai[66]
BirdsRheidaeDiogenornis fragilis[7]
CuculidaeEutreptodactylus itaboraiensis[68]
CariamaeItaboravis elaphrocnemoides
[69]
PsilopteridaePaleopsilopterus itaboraiensis[7]
SnakesAniliidaeHoffstetterella brasiliensis[70]
Coniophis cf. precedens[71]
BoidaeCorallus priscus[72]
Hechtophis austrinus[73]
Itaboraiophis depressus[74]
Paraungaliophis pricei[75]
Paulacoutophis perplexus[76]
Waincophis cameratus[77]
Waincophis pressulus[78]
MadtsoiidaeMadtsoia camposi[79]
Russellophiidae?Russellophiidae indet.[80]
CrocodyliformsCrocodilesSahitisuchus fluminensis
[81]
Eocaiman itaboraiensis[82]
AmphibiansCaeciliansApodops pricei[35]
FrogsXenopus romeri[35]
MollusksGastropodsAustrodiscus lopesi[83]
Biomphalaria itaboraiensis[84][85]
"Brachypodella" britoi[86][85]
Brasilennea arethusae
[87]
Brasilennea guttula
[88]
Brasilennea minor
[88]
Bulimulus fazendicus
[89][85]
Bulimulus trindadeae
[90][85]
Cecilioides sommeri
[91][85]
Cortana carvalhoi
[92][85]
Cyclodontina coelhoi[93]
Eoborus fusiforme
[94][85]
Eoborus rotundus
[95][85]
Eoborus sanctijosephi
[96][85]
Gastrocopta itaboraiensis[84][85]
Gastrocopta mezzalirai[97][85]
Itaborahia lamegoi
[98][85]
Leiostracus ferreirai[85]
Plagiodontes aff. dentatus[99][85]
Temesa magalhaesi
[100]
Strophocheilus sp.[37]
FloraPollenEchitricolpites polaris, Foveotriletes margaritae, Verrutriporites lunduensis[21]

Itaboraian correlations

Itaboraian correlations in South America
FormationItaboraíLas FloresKoluel KaikeMaíz GordoMuñaniMogollónBogotáCerrejónYpresian (IUCS) • Wasatchian (NALMA)
Bumbanian (ALMA) • Mangaorapan (NZ)
BasinItaboraíGolfo San JorgeSaltaAltiplano BasinTalara &
Tumbes		Altiplano
Cundiboyacense		Cesar-Ranchería
Itaboraí Formation is located in South America
Itaboraí Formation
Itaboraí Formation
Itaboraí Formation
Itaboraí Formation
Itaboraí Formation
Itaboraí Formation
Itaboraí Formation
Itaboraí Formation
Itaboraí Formation (South America)
Country Brazil Argentina Peru Colombia
Carodnia
Gashternia
Henricosbornia
Victorlemoinea
Polydolopimorphia
Birds
Reptiles
Fish
Flora
EnvironmentsAlluvial-lacustrineAlluvial-fluvialFluvio-lacustrineLacustrineFluvialFluvio-deltaic
Itaboraian volcanoclastics

Itaboraian fauna

Itaboraian flora
VolcanicYes

See also

References

  1. 1 2 Riccomini et al., 2004, p.401
  2. ↑ Kellner & Campos, 1999, p.399
  3. ↑ Bragança Júnior, 1992
  4. ↑ Carvalho, 1987, p.47
  5. ↑ Riccomini et al., 2004, p.390
  6. ↑ Santos & Carvalho, 2012, p.332
  7. 1 2 3 4 Mayr et al., 2011, p.679
  8. ↑ Riccomini, 1990, p.68
  9. ↑ Kellner & Campos, 1999, p.246
  10. ↑ Riccomini et al., 2004, p.384
  11. 1 2 3 Oliveira & Goin, 2011, p.107
  12. ↑ Modenesi-Gauttieri et al., 2002, p.258
  13. 1 2 Oliveira & Goin, 2011, p.108
  14. ↑ Torres Tiago, 2017, p.25
  15. ↑ Torres Tiago, 2017, p.26
  16. ↑ Torres Tiago, 2017, p.27
  17. ↑ Valente et al., 2017, p.227
  18. ↑ Oliveira et al., 2016, p.2
  19. ↑ Woodburne et al., 2014, p.116
  20. ↑ Woodburne et al., 2014, p.112
  21. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Oliveira & Goin, 2011, p.109
  22. ↑ Ezcurra & Agnolín, 2012, p.560
  23. ↑ Woodburne et al., 2013, p.7
  24. ↑ Sedor, 2017, p.39
  25. ↑ De Taranto et al., 2011, p.R58
  26. ↑ Pinheiro et al., 2013, p.328
  27. ↑ Bergqvist & Bastos, 2011, p.370
  28. ↑ Bergqvist, 2008, p.107
  29. ↑ Bergqvist, 2008, p.108
  30. ↑ Salvador & Simone, 2013a, p.42
  31. ↑ Pinheiro et al., 2013, p.329
  32. ↑ Bergqvist & Bastos, 2011, p.367
  33. ↑ Wells, 1996, p.35
  34. ↑ Itaboraí snakes at Fossilworks.org
  35. 1 2 3 Portland Quarry at Fossilworks.org
  36. 1 2 3 4 5 6 São José de Itaboraí at Fossilworks.org
  37. 1 2 São José 700 m at Fossilworks.org
  38. ↑ Carneiro, 2019, p.5
  39. ↑ Oliveira, 1998, p.148
  40. 1 2 3 4 5 6 7 8 9 10 11 12 13 Ladevèze & De Muizon, 2010, p.759
  41. ↑ Carneiro & Oliveira, 2017a, p.357
  42. ↑ Goin & Oliveira, 2007, p.310
  43. ↑ Oliveira & Goin, 2015, p.99
  44. ↑ Oliveira & Goin, 2015, p.101
  45. 1 2 Oliveira et al., 2016, p.4
  46. ↑ Carneiro et al., 2018, p.121
  47. ↑ Goin et al., 2016, p.85
  48. ↑ Oliveira & Goin, 2011, p.114
  49. ↑ Oliveira & Goin, 2011, p.112
  50. 1 2 Goin et al., 2016, p.86
  51. 1 2 3 4 5 Ladevèze, 2004, p.202
  52. 1 2 Ladevèze & De Muizon, 2010, p.747
  53. ↑ Carneiro & Oliveira, 2017b, p.499
  54. ↑ Carneiro et al., 2018, p.122
  55. ↑ Bergqvist et al., 2004, p.325
  56. ↑ Oliveira & Bergqvist, 1998, p.36
  57. ↑ Bergqvist, 2010, p.858
  58. ↑ Goin et al., 2016, p.87
  59. ↑ Bergqvist, 2008, p.119
  60. ↑ Bergqvist, 2008, p.113
  61. ↑ Mones, 2015, p.1
  62. ↑ Bergqvist, 2010, p.860
  63. ↑ Bergqvist, 2010, p.861
  64. ↑ Bergqvist, 2010, p.859
  65. ↑ Bergqvist, 2008, p.124
  66. 1 2 Goin et al., 2016, p.89
  67. ↑ Beck, 2016, p.8
  68. ↑ Mayr et al., 2011, p.682
  69. ↑ Mayr et al., 2011, p.680
  70. ↑ Rage, 1998, p.133
  71. ↑ Rage, 1998, p.131
  72. ↑ Rage, 2001, p.122
  73. ↑ Rage, 2001, p.116
  74. ↑ Rage, 2008, p.46
  75. ↑ Rage, 2008, p.41
  76. ↑ Rage, 2008, p.52
  77. ↑ Rage, 2001, p.130
  78. ↑ Rage, 2001, p.126
  79. ↑ Rage, 1998, p.116
  80. ↑ Rage, 2008, p.58
  81. ↑ Kellner et al., 2014, p.2
  82. ↑ Pinheiro et al., 2013, p.330
  83. ↑ Salvador & Simone, 2013a, p.12
  84. 1 2 Salvador & Simone, 2013a, p.28
  85. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Salvador & Simone, 2013b, p.4
  86. ↑ Salvador & Simone, 2013a, p.26
  87. ↑ Salvador & Simone, 2013a, p.9
  88. 1 2 Salvador & Simone, 2013a, p.11
  89. ↑ Salvador & Simone, 2013a, p.15
  90. ↑ Salvador & Simone, 2013a, p.16
  91. ↑ Salvador & Simone, 2013a, p.14
  92. ↑ Salvador & Simone, 2013a, p.17
  93. ↑ Salvador & Simone, 2013a, p.21
  94. ↑ Salvador & Simone, 2013a, p.25
  95. ↑ Salvador & Simone, 2013a, p.23
  96. ↑ Salvador & Simone, 2013a, p.24
  97. ↑ Salvador & Simone, 2013a, p.27
  98. ↑ Salvador & Simone, 2013a, p.19
  99. ↑ Salvador & Simone, 2013a, p.22
  100. ↑ Salvador & Simone, 2013a, p.13

Bibliography

General
Geology
Paleontology
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