The Adamantina Formation is a geological

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

in the Bauru Basin of western

São Paulo state SAO or Sao may refer to: Places * Sao civilisation, in Middle Africa from 6th century BC to 16th century AD * Sao, a town in Boussé Department, Burkina Faso * Saco Transportation Center (station code SAO), a train station in Saco, Maine, U.S. ...

, in

southeastern Brazil The Southeast Region of Brazil ( pt, Região Sudeste do Brasil; ) is composed of the states of Espírito Santo, Minas Gerais, Rio de Janeiro and São Paulo. It is the richest region of the country, responsible for approximately 60% of the Brazilian ...

. Its strata date back to the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

epoch of the

Cretaceous Period The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of t ...

, during the Mesozoic Era. The formation is part of the

Bauru Group The Bauru Group is a geological group of the Bauru Sub-basin, Paraná Basin in Minas Gerais, São Paulo, General Salgado, Itapecuru-Mirim, Mato Grosso, Brazil whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils ...

in the northeastern

Paraná Basin The Paraná Basin ( pt, Bacia do Paraná, es, Cuenca del Paraná) is a large cratonic sedimentary basin situated in the central-eastern part of South America. About 75% of its areal distribution occurs in Brazil, from Mato Grosso to Rio Grande d ...

Geology

Dinosaur remains are among the fossils that have been recovered from the Adamantina Formation.Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, South America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 600-604. . According to some studies, the Adamantina Formation dates from the

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded b ...

to the

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. ...

stage (90-83.5 million years ago) of the late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

, other studies have found a much younger age -

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval ...

(83.5-66 million years ago) of the late Cretaceous. More recent studies lean into the latter category and an unpublished article abstract revealed at the Society of Vertebrate Paleontology in 2017 also argues that the

Allen Formation The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous (middle Campanian to early Maastrichtian.Salgado et al., 2007 Dinosaur remains are among the fossils that have been recovered from the formati ...

, Loncoche, and

Los Alamitos Formation The Los Alamitos Formation is a geological formation of the North Patagonian Massif in Rio Negro Province, northwestern Patagonia, Argentina, whose strata date back to the Late Cretaceous (Late Campanian to Maastrichtian). Dinosaur remains are amo ...

are all contemporaries and are no later than 72.1Ma in age. A zircon was found dating to 85.2 ± 2.7 Ma so this represents a maximum age.

Geological setting

During the

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...

, the supercontinent

Pangea Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...

started to drift apart due to the breakup of Gondwana and Laurasia.Rabassa, J. (2014). Some concepts on Gondwana landscapes: long-term landscape evolution, genesis, distribution and age. In Gondwana Landscapes in southern South America (pp. 9-46). Springer Netherlands. The breakup of Gondwana caused the formation of the large Parana Basin. This basin has a size of ~1,100,000km2 and can be found not only in Brazil but also in Paraguay, Uruguay, and Argentina. The separation of the supercontinent and the breakup of Brazil and Africa was accompanied by volcanism that caused large eruptions of flood basalts. These volcanic rocks formed the Serra Geral Formation which underlies the deposits of the Bauru Group. The Bauru Basin is a trough that, as Miall (1990) argues,Miall, A. D. (1990). Principles of sedimentary basin analysis (Vol. 633, p. 499). New York: Springer-Verlag. evolved due to “thermo-mechanical subsidence” during the Late Cretaceous, probably due to the breakup of Africa and India. The sediments reach a thickness of up to ~300 m and consist mainly of siliciclastic sediments. The Bauru Group can be subdivided into five different formations Souza Jr, J. J. (1984). O Grupo Bauru na porcao mais setentrional da Bacia Sedimentar do Paraná. In 33 Congresso Brasileiro de Geologia, Rio de Janeiro (Vol. 2, pp. 944-957).Dias-Brito, D., Musacchio, E. A., de Castro, J. C., Maranhão, M. S. A. S., Suárez, J. M., & Rodrigues, R. (2001). Grupo Bauru: uma unidade continental do Cretáceo no Brasil-concepções baseadas em dados micropaleontológicos, isotópicos e estratigráficos. Revue de Paléobiologie, 20(1), 245-304. from bottom to top: Caiua, Santo Anastacio, Adamantina, and Uberaba. Not all formations are equally well represented in the different states and differences occur according their sedimentary composition and therefore also in their naming.

Vertebrate paleofauna

Crurotarsans

Ornithodirans

Indeterminate dinosaur remains are known from the formation.

Lepidosaurs

Amphibians

Mammals

Eutheria Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distinguished from noneutherians by various phenotypic tra ...

incertae sedis, '' Brasilestes'' (

tribosphenida Tribosphenida is a group (infralegion) of mammals that includes the ancestor of ''Hypomylos'', Aegialodontia and Theria (the last common ancestor of marsupials and placentals plus all of its descendants). Its current definition is more or less sy ...

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

gondwanatheres Gondwanatheria is an extinct group of mammaliaforms that lived in parts of Gondwana, including Madagascar, India, South America, Africa and Antarctica during the Upper Cretaceous through the Paleogene (and possibly much earlier, if '' Allostaff ...

and meridiolestidans.Zofia Kielan-Jaworowska; Richard L. Cifelli; Zhe-Xi Luo (2004). "Chapter 7: Eutriconodontans". Mammals from the Age of Dinosaurs: origins, evolution, and structure. New York: Columbia University Press. pp. 216–248. .

References

{{Reflist, 24em Geologic formations of Brazil Cretaceous Brazil Sandstone formations Mudstone formations Siltstone formations Conglomerate formations Coal formations Coal in Brazil Alluvial deposits Fluvial deposits Lacustrine deposits Aeolian deposits Cretaceous paleontological sites of South America Paleontology in Brazil Environment of São Paulo (state) Landforms of São Paulo (state)