Barreiras Formation

Barreiras Formation
Barreiras Group

Stratigraphic range:
Cliffs in Icapuí, Ceará
TypeGeological formation
Thickness212 metres (696 ft)
Lithology
PrimarySandstone, siltstone
Location
CountryBrazil
ExtentRio de Janeiro – Amapá

Distribution of the Barreiras Formation (Brazilian Society of Geology, 2021)

The Barreiras Formation (Portuguese: Formação Barreiras) or the Barreiras Group (Grupo Barreiras) is a geological formation that gives rise to most of the cliffs along the Brazilian coast. It dates from the Cenozoic epoch and consists of sedimentary rock. It extends from the north of the state Rio de Janeiro to the south of Amapá.[1]

Geology

The name Barreiras translates as "barrier". In various places along the coast, the term refers to the obstacles posed by the cliffs for those wanting to travel between inland Brazil and the Atlantic Ocean. In the Letter of Pero Vaz de Caminha from 1500, he already wrote to King Manuel I of Portugal:

"[The land] presents along the sea in some parts large barriers (barreiras), some red and some white, and the land above is completely flat and full of large groves.”[2]

The first time Barreiras was mentioned as part of geological research was in the work that J.C. Branner conducted in 1902 around the Paratibe River in the state Pernambuco.[3] However, until the present day there is no academic consensus which of the terms Barreiras Formation or Barreiras Group is the correct one.

The deposition of the Barreiras Formation was highly conditioned by tectonic processes that affect the South American platform since the Middle Miocene. These include episodes of epeirogenic uplift and continental flexure that deposited sediments in a long, narrow basin parallel to the coast.[5] The large extension of the formation along the Brazilian coastline points to a connection to events on a continental scale, such as the opening of the South Atlantic Ocean and the formation of the Andes.[6]

The Barreiras Formation is characterised by alternating lenticular layers of sandstone and siltstone of varying colours.[7][8][9] Where the rock is laterised, ferruginous concretions can be observed.[10]

Use

Sand is extracted from the Barreiras Formation for use in civil construction. Pebbles and gravel are used in ball mills or for the confection of handicrafts.[11]

References

  1. ^ Chrismann, J.V.V. (2014). Mapeamento da Formação Barreiras na região norte fluminense,entre os rios Paraíba do sul e Itabapoana (Thesis). Federal University of Rio de Janeiro.
  2. ^ Vaz de Caminha, P. (1500). "Carta de Pero Vaz de Caminha".
  3. ^ Branner, J.C. (1902). "Geology along the Pernambuco coast south of Recife". Geological Society of America Bulletin. 13: 58–92.
  4. ^ Da Câmara, I.F.; Barros, E.L.; Da Silva, R.R. (2021). "Caracterização Sedimentológica da Praia de Morro Branco, Litoral Leste Cearense: Uma Análise Espaço-temporal". Revista Brasileira de Geografia Física. 7: 3788–3803. doi:10.26848/rbgf.v14.7.p3788-3803.
  5. ^ Andrade, G.O.; Lins, R.C. (1963). Introdução à morfoclimatologia do Nordeste do Brasil. Congresso Brasileiro de Geologia. Recife: Sociedade Brasileira de Geologia.
  6. ^ Suguio, K.; Bidegain, J.C.; Mörner, N.A. (1986). "Dados preliminares sobre as idades paleomagnéticas do Grupo Barreiras e da Formação São Paulo". Revista Brasileira de Geociências. 2: 171–175.
  7. ^ Companhia Baiana de Pesquisa (2000). Projeto Costa do Descobrimento. CBPM/CPRM/UFBA-LEC/CPGG.
  8. ^ Vilas Bôas, G.S.; Sampaio, F.J.; Pereira, A.M.S. (2001). "The Barreiras Group in the Northeastern coast of the State of Bahia, Brazil: depositional mechanisms and processes". Anais da Academia Brasileira de Ciências. 73 (3): 417–427. doi:10.1590/S0001-37652001000300010.
  9. ^ Mello, J.C. (1999). Estudos hidrogeológicos do Aquífero Barreiras uma contribuição para o desenvolvimento sustentado dos tabuleiros costeiros do estado da Bahia (Thesis). Salvador: Federal University of Bahia.
  10. ^ Moura-Fé, M.M. (2008). Caracterização Geral da Formação Barreiras na Região Metropolitana de Fortaleza (RMF), Ceará - Brasil. 2° Encontro Latino-Americano de Geomorfologia. Anais de Trabalhos Completos do VII Simpósio Nacional de Geomorfologia.
  11. ^ Neumann, V.H.M.L. (2014). "Folha Cabedelo, SB.25-Y-A-VI". Companhia de Pesquisa de Recursos Minerais.
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