{"id":538796,"date":"2025-01-14T15:22:04","date_gmt":"2025-01-14T18:22:04","guid":{"rendered":"https:\/\/revistapesquisa.fapesp.br\/?p=538796"},"modified":"2025-01-14T15:22:04","modified_gmt":"2025-01-14T18:22:04","slug":"extinct-rivers-of-the-northeast","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/extinct-rivers-of-the-northeast\/","title":{"rendered":"Extinct rivers of the Northeast"},"content":{"rendered":"

If you are in the region of Sobral and Juazeiro do Norte, in Cear\u00e1 State; Catimbau, in Pernambuco; or Monsenhor Hip\u00f3lito, in Piau\u00ed, you will probably find sandstones \u2014 yellowish rocks formed by sand compaction, whose layers indicate that millions of years ago, a river ran through these areas. Additionally, in the flat areas to the south, covering the states of Sergipe, Alagoas, Bahia, and Pernambuco, there were mountains between 3,000 and 4,000 meters (m) in altitude.<\/p>\n

\u201cThe rivers that ran through the Brazilian Northeast between 480 million and 445 million years ago were different from those found there today,\u201d comments geologist Rodrigo Cerri, of S\u00e3o Paulo State University (UNESP). \u201cThey were possibly intertwined, and transported sediment through vast, gently undulating areas, probably with no vegetation.\u201d<\/p>\n

Cerri says that there was a network or system of rivers, each 300 to 500 kilometers (km) long \u2014 more extensive, therefore, than the Capibaribe, at 240 km, whose source is in the sert\u00e3o <\/em>(badlands) of Pernambuco, passing through state capital Recife to the sea. Although different in origin, they would have been similar to the S\u00e3o Francisco or Amazonas rivers, with sources in the mountains of Minas Gerais and the Peruvian Andes respectively, making their way to the Atlantic Ocean.<\/p>\n

Four hundred million years ago, the region that would become northeastern Brazil was still joined to what is currently North Africa, forming a continuous geological chain that extended to the Middle East, with rivers descending from the mountains, also now extinct. As the Atlantic had not yet been formed, the rivers discharged into the sea north of the current Brazilian northeastern region and the west of Africa, in sections where the two continents had moved apart.<\/p>\n

\"\"

Rodrigo Cerri\u2009\/\u2009Unesp<\/span>Sandstone layers indicating accumulation of sediments brought by waterwaysRodrigo Cerri\u2009\/\u2009Unesp<\/span><\/p><\/div>\n

This separation concluded around 100 million years ago, when the last rocky mass of 425 km, which connected what is today the state of Rio Grande do Norte and the south of Pernambuco to the coast of what are currently Nigeria, Cameroon, and Equatorial Guinea, is believed to have broken up; the Atlantic then had the space to form and widen.<\/p>\n

Cerri drew these conclusions by examining sandstones collected in 2021 and 2022 from seven sedimentary basins (normally low-lying areas that accumulate silt) in the states of Cear\u00e1, Piau\u00ed, and Pernambuco. He says that the thick sandstone layers, built up over millions of years, present structures indicating the direction of the river after it was covered by other rocks and vegetation.<\/p>\n

At the Rio Claro UNESP facility, Cerri ground the rocks and prepared seven samples, from which he extracted grains of the mineral zircon, with an average diameter of 300 micra (1 micrometer \u2014 plural micra \u2014 equals 1 thousandth of a millimeter). The zircon crystals incorporate chemical elements from the environment in which they are brought into being, based on magma, the viscous material forming the inside of Earth. The amount and type of each element indicate when and at what temperature and pressure the rocks containing zircon were formed.<\/p>\n

One of zircon\u2019s chemical elements is uranium, which, being radioactive, transforms \u2014 or decays \u2014 into a form of another element: lead. Older rocks contain less uranium (or more lead) and younger ones have more uranium (or less lead). A laser device zapped the mineral and transformed the uranium and lead into vapor. A mass spectrometer determined the proportion of the two components, and in turn the age of the rocks. The results indicate that the zircon probably came from older, and therefore higher lands than those on which they were found \u2014 geologically more recent and lower.<\/p>\n

According to Cerri, the rivers disappeared and were covered in ice by intense glaciation at the end of the Ordovician geological period, between 445 million and 443 million years ago, as detailed in a June 2022 article published in Geological Magazine<\/em> and another in the July issue of Gondwana Research<\/em>.<\/p>\n\n \n \n \n <\/picture>Alexandre Affonso \/ Revista Pesquisa FAPESP<\/span>\n

\u201cFor some time, the discussion has been around whether river sediments in the Parna\u00edba basin across the states of Piau\u00ed, Maranh\u00e3o, and Cear\u00e1, had the same origin as other basins in the Northeast,\u201d says Cerri. \u201cBy studying zircon, we have demonstrated that all sedimentary units could indeed be of the same age, and have formed in the same manner.\u201d<\/p>\n

Geologist David Vasconcelos, of the Federal University of Campina Grande (UFCG), did not participate in the project, but studies sedimentary basins in Brazil\u2019s Northeast region, and considers the hypothesis to be valid: \u201cThe older geological units of the northeastern sedimentary basins may really have had a common origin, despite the different regional names of the same type of sandstone.\u201d Vasconcelos says that 480 million years ago, the rivers in these currently isolated basins may have been integrated in the so-called Afro-Brazilian Depression, formed by today\u2019s Northeast Brazil and West Africa, vaster than the Amazon Basin.<\/p>\n

\u201cThere is coherence in the information gathered, but you cannot a priori<\/em> rule out that northeastern catchments had sources of sediments originating from several different sites, because rocks of the same age may occur in differing locations,\u201d observes geologist Ticiano dos Santos, of the Institute of Geology at the University of Campinas (IG-UNICAMP), who did not participate in Cerri\u2019s project, and studies the even more ancient geological history of the region, going back at least 550 million years, particularly in Cear\u00e1 State. \u201cAt the mouth of the Amazon, for example, there are zircons of all ages from the Andes and older areas occurring along the Amazon River.\u201d<\/p>\n

Well known to geologists, the mountains of the current Brazilian Northeast formed in areas previously occupied by the sea as a result of the encounter between rocky blocks of the lithosphere (the surface layer of Earth) moving in the opposite direction. One of the high areas, the Sergipana Belt, currently covers the state of Sergipe and part of Bahia and Alagoas. Another, the Riacho do Pontal Belt, occupies the border region between the states of Bahia, Pernambuco, and Piau\u00ed, on the northern margin of the S\u00e3o Francisco craton (a craton is a block of ancient rocks extending for hundreds of kilometers).<\/p>\n

Anyone moving around the interior of Brazil\u2019s Northeast region who does not know much about geology should be careful not to draw hasty conclusions. Chapada do Araripe, for example, even at an altitude of 1,000 m and with 178 km of extension, is not a remnant of a mountain, but the result of compression of the denser rocky structures that surround it.<\/p>\n

Projects
\n1.<\/strong> Geochronology and provenance of basal successions in the Parna\u00edba, Araripe, Jatob\u00e1, and Tucano Norte basins: Implications for the origin of the SW Gondwana intracontinental basins (n\u00ba 20\/10739-7<\/u><\/a>); Grant Mechanism <\/strong>Postdoctoral Fellowship; Supervisor<\/strong> Lucas Verissimo Warren (UNESP); Beneficiary <\/strong>Rodrigo Irineu Cerri; Investment<\/strong> R$271,323.36.
\n2.<\/strong> U-Pb and sedimentary provenance analyzes of rutiles by LA-ICP-MS in the Paleozoic sequences of the Borborema province: Parna\u00edba, Araripe, and Tucano-Jatob\u00e1 Basins (n\u00ba 21\/12621-6<\/u><\/a>); Modality<\/strong> Postdoctoral Fellowship; Supervisor<\/strong> Lucas Verissimo Warren (UNESP); Beneficiary<\/strong> Rodrigo Irineu Cerri; Investment<\/strong> R$156,768.04.<\/p>\n

Scientific articles<\/strong>
\nCERRI, R. I. et al<\/em>. The Early Paleozoic sedimentary record in northeastern Brazil: Unravelling the sedimentary provenance and evolution of fluvial systems after the western Gondwana assembly<\/a>. Gondwana Research<\/strong>. vol. 131, pp. 237\u201355. july 2024.
\nCERRI, R. I. et al<\/em>. So close and yet so far: U\u2013Pb geochronological constraints of the Jaibaras rift basin and the intracratonic Parna\u00edba basin in SW Gondwana<\/a>. Geological Magazine<\/strong>. vol. 159, no. 7. apr. 6, 2021.
\nGOMES, N. G. et al<\/em>. P-T-t reconstruction of a coesite-bearing retroeclogite reveals a new UHP occurrence in the western Gondwana margin (NE-Brazil)<\/a>. Lithos<\/strong>. vol. 446\u20137, 107138. june 2023.<\/p>\n","protected":false},"excerpt":{"rendered":"Sedimentary rock layers indicate that waters descended from mountains in the region some 450 million years ago","protected":false},"author":17,"featured_media":538802,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[159],"tags":[200,239,240],"coauthors":[5968],"class_list":["post-538796","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science","tag-environment","tag-geography","tag-geology","position_at_home-sumario"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/538796","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/17"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=538796"}],"version-history":[{"count":2,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/538796\/revisions"}],"predecessor-version":[{"id":538815,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/538796\/revisions\/538815"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media\/538802"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=538796"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=538796"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=538796"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=538796"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}