Itaboraí Formation Explained

Itaboraí Formation
Type:	Geological formation
Period:	Ypresian
Age:	Early Eocene (Itaboraian) ~
Prilithology:	Limestone, marl
Otherlithology:	Travertine, lignite
Namedfor:	Itaboraí
Namedby:	Leinz
Year Ts:	1938
Region:	Rio de Janeiro
Coordinates:	-22.1°N -41.6°W
Paleocoordinates:	-25°N -30°W
Subunits:	See text
Underlies:	Early Eocene basalt &<br>Late Eocene to Early Oligocene conglomerates (Rio Frio Formation)
Overlies:	Precambrian basement
Thickness:	up to 100m (300feet)
Extent:	Itaboraí Basin
Area:	1km2

The Itaboraí Formation (pt|Formação Itaboraí) is a highly fossiliferous geologic formation and Lagerstätte^[1] of the Itaboraí Basin in Rio de Janeiro, southeastern Brazil. The formation reaching a thickness of 100m (300feet) 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 1km2 around the city of Itaboraí, 34km (21miles) 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 100m (300feet) 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)^[2]
• "River of brilliant stones", derived from the words itá (stone), berab (brilliant) and y (river)^[3]

Description

The Itaboraí Formation is restricted to the Itaboraí Basin, a minibasin stretching across an area of 1km2 of 1400m×500mm (4,600feet×1,600feetm), in the vicinity of Itaboraí 34km (21miles) northeast of Rio de Janeiro, southeastern Brazil.^[4] 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.^[5] The now abandoned and largely inaccessible limestone quarries of this locality have yielded a diverse mammalian fauna from early late Paleocene fissure fillings. The sediments of the formation were described by Leinz in 1938.^[6] Presently, the basin is filled up with water impeding any collecting activity.^[7]

Basin history

The small basin, a small half-graben, is the oldest^[8] and smallest^[9] of several Cenozoic rift basins stretching across 1000km (1,000miles) 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.^[10]

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.^[11]

Stratigraphy

The Itaboraí Formation rests unconformably on top of the Precambrian Paraíba do Sul Group, part of the Meso- to Neoproterozoic Paraíba do Sul Complex.^[12] The Paleogene succession of the minibasin reaches a thickness of 100m (300feet) and consists of three depositional sequences, with the Itaboraí Formation representing the first two;^[13]

• 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.^[9]
• 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^[9]
• 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,^[14] have been correlated with the Eocene to Oligocene Resende Formation of the eponymous basin.^[11]

The Itaboraí Formation is separated from Sequence 3 by basaltic volcanic rocks, formed in the Early Eocene.^[15]

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.^[16]

Age

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),^{[17] [18]} spanning polarity chron 23.^[19] 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.^[20] During this time, a biogeographical connection existed with Antarctica and, though separated by the developing South Atlantic, with Africa.^[21] The deposits of the formation were formed during the Early Eocene Climatic Optimum (EECO), just after the Paleocene-Eocene Thermal Maximum.^[22]

Paleontological significance

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.^[23]

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.^[24] In the Paleocene of the southern hemisphere, small terrestrial birds have only been discovered in the late Paleocene fissure fillings of the Itaboraí Formation.^[25]

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]}

Class	Group	Fossils	Images	class=unsortable	Notes
Mammals	Marsupials	Bergqvistherium primigenia		align=center	^[38]
		Carolocoutoia ferigoloi		align=center	^[39]
		Carolopaulacoutoia itaboraiensis		align=center
		Derorhynchus singularis		align=center
		Didelphopsis cabrerai		align=center
		Eobrasilia coutoi		align=center	^[40] ^[41]
		Gashternia carioca		align=center	^[42]
		Gaylordia macrocynodonta		align=center	^[43]
		Gaylordia mater		align=center	^[44]
		Guggenheimia brasiliensis		align=center
		Guggenheimia crocheti		align=center
		Itaboraidelphys camposi		align=center
		Marmosopsis juradoi		align=center
		Minusculodelphis minimus		align=center	^[45]
		Minusculodelphis modicum		align=center
		Mirandatherium alipioi		align=center
		Monodelphopsis travassosi		align=center	^[46]
		Periprotodidelphis bergqvistae		align=center	^[47]
		Protodidelphis mastodontoides		align=center	^[48]
		Protodidelphis vanzolinii		align=center	^[49]
		Riolestes capricornicus		align=center	^[50]
		Xenodelphis doelloi		align=center
				align=center	^[51]
		Zeusdelphys complicatus		align=center	^[52]
		Austropediomys marshalli		align=center	^[53]
				align=center
				align=center	^[54]
	Armadillos	Riostegotherium yanei		align=center	^[55] ^[56]
		Tetragonostylops apthomasi		align=center	^[57]
		Lamegoia conodonta		align=center	^[58] ^[59]
		Ricardocifellia protocenica syn. Paulacoutoia protocenica		align=center	^[60] ^[61]
	Litopterns	Asmithwoodwardia scotti		align=center
		Miguelsoria parayirunhor		align=center	^[62]
		Paranisolambda prodromus		align=center	^[63]
		Protolipterna ellipsodontoides		align=center	^[64]
		Victorlemoinea prototypica		align=center	^[65]
		Camargomendesia pristina		align=center
		Colbertia magellanica		align=center
		Homalostylops atavus		align=center
		Henricosbornia sp.		align=center
		Nanolophodon tutuca		align=center
				align=center
	Sparassodonts	Palaeocladosictis mosesi		align=center
		Patene simpsoni		align=center
		?Arminiheringia sp.		align=center
				align=center
				align=center
		Bobbschaefferia fluminensis		align=center
		Epidolops ameghinoi		align=center	^[66]
				align=center
		Procaroloameghinia pricei		align=center
	Carodnia vieirai		align=center	^[67]
Birds		Diogenornis fragilis		align=center
		Eutreptodactylus itaboraiensis		align=center	^[68]
		Itaboravis elaphrocnemoides		align=center	^[69]
		Paleopsilopterus itaboraiensis		align=center
Snakes		Hoffstetterella brasiliensis		align=center	^[70]
		Coniophis cf. precedens		align=center	^[71]
		Corallus priscus		align=center	^[72]
		Hechtophis austrinus		align=center	^[73]
		Itaboraiophis depressus		align=center	^[74]
		Paraungaliophis pricei		align=center	^[75]
		Paulacoutophis perplexus		align=center	^[76]
		Waincophis cameratus		align=center	^[77]
		Waincophis pressulus		align=center	^[78]
		Madtsoia camposi		align=center	^[79]
				align=center	^[80]
	Crocodiles	Sahitisuchus fluminensis		align=center	^[81]
		Eocaiman itaboraiensis		align=center	^[82]
Amphibians	Caecilians	Apodops pricei		align=center
		Xenopus romeri		align=center
	Gastropods	Austrodiscus lopesi		align=center	^[83]
		Biomphalaria itaboraiensis		align=center	^[84]
		"Brachypodella" britoi		align=center	^[85]
		Brasilennea arethusae		align=center	^[86]
		Brasilennea guttula		align=center	^[87]
		Brasilennea minor		align=center
		Bulimulus fazendicus		align=center	^[88]
		Bulimulus trindadeae		align=center	^[89]
		Cecilioides sommeri		align=center	^[90]
		Cortana carvalhoi		align=center	^[91]
		Cyclodontina coelhoi		align=center	^[92]
		Eoborus fusiforme		align=center	^[93]
		Eoborus rotundus		align=center	^[94]
		Eoborus sanctijosephi		align=center	^[95]
		Gastrocopta itaboraiensis		align=center
		Gastrocopta mezzalirai		align=center	^[96]
		Itaborahia lamegoi		align=center	^[97]
		Leiostracus ferreirai		align=center	^[98]
		Plagiodontes aff. dentatus		align=center	^[99]
		Temesa magalhaesi		align=center	^[100]
		Strophocheilus sp.		align=center
		Echitricolpites polaris, Foveotriletes margaritae, Verrutriporites lunduensis		align=center

Itaboraian correlations

Itaboraian correlations in South America

Formation	Itaboraí								Ypresian (IUCS) • Wasatchian (NALMA) Bumbanian (ALMA) • Mangaorapan (NZ)
Basin									align=center rowspan=11
Carodnia	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Gashternia	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Henricosbornia	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Victorlemoinea	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Birds	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
Reptiles	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
	align=center		align=center		align=center		align=center		align=center		align=center		align=center		align=center
	Alluvial-lacustrine	Alluvial-fluvial		Fluvio-lacustrine	Lacustrine	Fluvial	Fluvio-deltaic
Volcanic			Yes

See also

• South American land mammal ages
• Iguape Formation, contemporaneous formation of the Santos Basin
• Laguna del Hunco Formation, contemporaneous fossiliferous formation of the Cañadón Asfalto Basin, Argentina
• Lefipan Formation, pre-Tiupampan fossiliferous lacustrine formation of the Cañadón Asfalto Basin, Argentina
• Bogotá Formation, contemporaneous fossiliferous formation of central Colombia
• Green River Formation, contemporaneous fossiliferous formation of Colorado, Wyoming and Utah
• Klondike Mountain Formation, contemporaneous fossiliferous formation of Washington State
• La Meseta Formation, contemporaneous fossiliferous formation of Antarctica

References

Bibliography

General

Geology

Paleontology

Notes and References

1. Kellner & Campos, 1999, p.399
2. Bragança Júnior, 1992
3. Carvalho, 1987, p.47
4. Riccomini et al., 2004, p.390
5. Santos & Carvalho, 2012, p.332
6. Riccomini, 1990, p.68
7. Kellner & Campos, 1999, p.246
8. Riccomini et al., 2004, p.384
9. Oliveira & Goin, 2011, p.107
10. Modenesi-Gauttieri et al., 2002, p.258
11. Oliveira & Goin, 2011, p.108
12. Torres Tiago, 2017, p.25
13. Torres Tiago, 2017, p.26
14. Riccomini et al., 2004, p.401
15. Torres Tiago, 2017, p.27
16. Valente et al., 2017, p.227
17. Oliveira et al., 2016, p.2
18. Woodburne et al., 2014, p.116
19. Woodburne et al., 2014, p.112
20. Oliveira & Goin, 2011, p.109
21. Ezcurra & Agnolín, 2012, p.560
22. Woodburne et al., 2013, p.7
23. Sedor, 2017, p.39
24. De Taranto et al., 2011, p.R58
25. Mayr et al., 2011, p.679
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. https://paleobiodb.org/classic/displayCollResults?collection_no=48091 Itaboraí snakes
35. https://paleobiodb.org/classic/displayCollResults?collection_no=77193 Portland Quarry
36. https://paleobiodb.org/classic/displayCollResults?collection_no=118314 São José de Itaboraí
37. https://paleobiodb.org/classic/displayCollResults?collection_no=38793 São José 700 m
38. Carneiro, 2019, p.5
39. Oliveira, 1998, p.148
40. Carneiro & Oliveira, 2017a, p.357
41. Ladevèze & De Muizon, 2010, p.759
42. Goin & Oliveira, 2007, p.310
43. Oliveira & Goin, 2015, p.99
44. Oliveira & Goin, 2015, p.101
45. 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. Goin et al., 2016, p.86
51. Ladevèze & De Muizon, 2010, p.747
52. Carneiro & Oliveira, 2017b, p.499
53. Carneiro et al., 2018, p.122
54. Ladevèze, 2004, p.202
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. Beck, 2016, p.8
67. Goin et al., 2016, p.89
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. Salvador & Simone, 2013a, p.28
85. Salvador & Simone, 2013a, p.26
86. Salvador & Simone, 2013a, p.9
87. Salvador & Simone, 2013a, p.11
88. Salvador & Simone, 2013a, p.15
89. Salvador & Simone, 2013a, p.16
90. Salvador & Simone, 2013a, p.14
91. Salvador & Simone, 2013a, p.17
92. Salvador & Simone, 2013a, p.21
93. Salvador & Simone, 2013a, p.25
94. Salvador & Simone, 2013a, p.23
95. Salvador & Simone, 2013a, p.24
96. Salvador & Simone, 2013a, p.27
97. Salvador & Simone, 2013a, p.19
98. Salvador & Simone, 2013b, p.4
99. Salvador & Simone, 2013a, p.22
100. Salvador & Simone, 2013a, p.13