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Adamantina Formation
The Adamantina Formation is a geological formation in Brazil whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the 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. ISBN 0-520-24209-2.〕 According to most studies,〔 the Adamantina Formation dates from the Turonian to the Santonian stage (90-83.5 million years ago) of the late Cretaceous, although some studies found much younger age - Campanian to Maastrichtian (83.5-66 million years ago) of the late Cretaceous.
==Geological setting==
During the Early Jurassic, the supercontinent Pangea 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.〔Goldberg, K., & Garcia, A. J. (2000). Palaeobiogeography of the Bauru Group, a dinosaur-bearing Cretaceous unit, northeastern Paraná Basin, Brazil. Cretaceous Research, 21(2), 241-254〕 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.〔Candeiro, C. R. A., Abranches, C. T., Abrantes, E. A., Avilla, L. D. S., Martins, V. C., Moreira, A. L., ... & Bergqvist, L. P. (2004). Dinosaurs remains from western São Paulo state, Brazil (Bauru Basin, Adamantina Formation, Upper Cretaceous). Journal of South American Earth Sciences, 18(1), 1-10.〕 The Bauru Group can be subdivided into five different formations 〔〔Soares, P. C., Landim, P. M. B., Fulfaro, V. J., & Neto, A. S. (1980). Ensaio de caracterização estratigráfica do Cretáceo no estado de São Paulo: Grupo Bauru. Brazilian Journal of Geology, 10(3), 177-185.〕〔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.〔
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