{"id":492338,"date":"2023-10-10T19:57:42","date_gmt":"2023-10-10T22:57:42","guid":{"rendered":"https:\/\/revistapesquisa.fapesp.br\/?p=492338"},"modified":"2023-12-06T13:38:35","modified_gmt":"2023-12-06T16:38:35","slug":"mountains-and-volcanoes-in-the-interior-of-ceara-2","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/mountains-and-volcanoes-in-the-interior-of-ceara-2\/","title":{"rendered":"Vestiges of the sea in the Amazon interior"},"content":{"rendered":"

Don’t be surprised if you encounter plants and animals in the Amazon rainforest that have similarities with marine organisms. Even though more than a thousand kilometers distant from the ocean, fossils of shells and sea centipedes, and teeth from sharks, stingrays, and other marine animals have been found in sediments several meters deep during surveys carried out in Brazil, Peru, and Colombia.<\/p>\n

They arrived as far as the interior of what is now dense jungle because the Caribbean Sea flooded the Amazon during the geological period known as the Miocene, from 23 million to 5 million years (Ma) ago. These conclusions emerge from analyses of sediment fossils from the banks of the Solim\u00f5es, Juru\u00e1, and Javari rivers that have been conducted since 1998 by a group from the Em\u00edlio Goeldi Museum of Par\u00e1 (MPEG), coordinated by biologist Maria In\u00eas Ramos, with teams from other institutions and support from the Brazilian National Council for Scientific and Technological Development (CNPq).<\/p>\n

\u201cFloods caused by seawater contributed to the high biodiversity of the Amazon by bringing in marine animals and separating populations that then originated new species, which adapted to the new environments,\u201d says geologist Lilian Maia Leandro, of Usinos University in Rio Grande do Sul State, lead author of the article published in January 2022 in the journal Geology<\/em><\/a>. A separate article describing the results came out in December in the Journal of South American Earth Sciences<\/em><\/a>. One example of this adaptation is the pink river dolphin, which seems to have evolved in the sea \u2014 its ancestors would have been dolphins \u2014 and today lives in the rivers of the Amazon.<\/p>\n

Investigating sediments extracted from drilling conducted during the 1970s by the Mineral Resources Research Company (CPRM) in the region under study, the MPEG team found an abundance of bivalve crustaceans called ostracods, currently found in coastal environments, and other marine organisms, such as foraminifera. When identified under a microscope, they showed more similarities with samples extracted from a core drilled in the Caribbean than with two other samples from the Pacific and Atlantic oceans.<\/p>\n

Another indication of marine influence in the Solim\u00f5es basin is the remnants of marine microalgae, also known as dinoflagellates, which live in plankton and are common in the Caribbean Sea. With an estimated age of between 23 Ma and 3.8 Ma, the microfossils indicate periods of higher salinity, resulting from the occupation of sea water in the Amazon.<\/p>\n

\u201cWe identified a pulsing pattern to the floods, which occurred approximately every 2 Ma or 3 Ma. The most pronounced inundation we detected was between 11.1 Ma and 8.8 Ma,\u201d says Ramos. Sea water would have increased the salinity of a gigantic group of lakes, the Pebas system, which then extended from Colombia and Peru to the central portion of the Brazilian Amazon.<\/p>\n

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Maria In\u00eas F. Ramos \/ MPEG<\/span>Foraminifera microfossil of the genus Ammonia and microcrustacean carapace of the genus Cyprideis, found on riverbanks or in boreholes in the western Brazilian AmazonMaria In\u00eas F. Ramos \/ MPEG<\/span><\/p><\/div>\n

\u201cThe sea probably entered from the Orinoco river valley, to the north,\u201d suggests Leandro. \u201cThe Andes already blocked the waters to the west, in Peru, but the M\u00e9rida Mountain range in Venezuela, which could also have barred the sea, had not yet formed.\u201d She believes the Caribbean Sea must have inundated South America at a time when the continent was flatter and unable to block the waters when the climate heated, glaciers melted, and the sea level rose.<\/p>\n

The MPEG team’s hypotheses about the inundations by the Caribbean Sea were reinforced by numerical models developed by geophysicist Victor Sacek, from the University of S\u00e3o Paulo (USP), which considered the internal dynamics of planet Earth and climate and sea level changes. According to his conclusion, described in an article published in March 2023 in the journal Earth and Planetary Science Letters<\/em><\/a>, water from the ocean to the north would have invaded the region intermittently for at least 35 Ma.<\/p>\n

The models show that the uplift of the Andes would have changed the region’s landscape, altering the flow of rivers and rainfall patterns. \u201cThe weight of the mountain range made the crust of South America bend, as if it were a trampoline, and form a depression near the Andes,\u201d explains Sacek. According to the model, this natural pool would have been flooded with Caribbean waters.<\/p>\n

\u201cThe convection processes of the Earth’s mantle contributed to curve the Earth’s crust downwards, creating depressions that extended into the center of the Amazon,\u201d he adds. \u201cThe models show that these depressions were initially filled with marine water and favored the formation of lacustrine environments.\u201d<\/p>\n

Over time, sediments from the Andes filled in the lakes, culminating in the formation of the Amazon River basin approximately 10 Ma ago. In Sacek’s numerical models, marine incursions into the Caribbean Sea in the Solim\u00f5es basin would have ended before the formation of the Amazon River. The conclusions, however, do not eliminate the possibility of more recent incursions, between 4.7 Ma and 3.8 Ma ago, as suggested by the MPEG team.<\/p>\n

\u201cSome of the differences between Sacek’s and Leandro’s results may be due to the scarcity of data to test the scenarios generated by numerical models and doubts regarding the living environments of the fossils,\u201d comments USP geologist Andr\u00e9 Sawakuchi, who did not participate in the studies. \u201cThe topic is controversial and there are a lot of uncertainties.\u201d Sawakuchi believes records of environmental changes in the Amazon are still very sparse and it would be risky to speak of climate variation millions of years ago, when there are only relatively reliable data for the last 250,000 years.<\/p>\n

Sawakuchi coordinates the Trans-Amazon Drilling Project (TADP), supported by FAPESP, with the participation of researchers from 12 countries, which has the goal of drilling in the Amazon from the Andes to the shores of the Atlantic. In addition to more precise data to feed the mathematical models, he hopes to verify whether the sea invaded the forest even earlier than indicated by Sacek’s calculations.<\/p>\n

Project<\/strong>
\nTransAmazon Drilling Project: Origin and evolution of the forests, climate, and hydrology of the South American tropics (n\u00ba 18\/23899-2<\/a>); Grant Mechanism<\/strong> Thematic Project \u2012 Global Climate Change Research Program; Principal Investigator<\/strong> Andr\u00e9 Oliveira Sawakuchi (USP); Investment<\/strong> R$9,659,178.81.<\/p>\n

Scientific articles
\n<\/strong>LEANDRO, L. M. et al<\/em>. Multi-proxy evidence of Caribbean-sourced marine incursions in the Neogene of Western Amazonia, Brazil<\/a>. Geology<\/strong>. vol. 50, no. 4, pp. 465\u2013469. jan. 5, 2022.
\n<\/strong>SANTOS, K. S. dos & RAMOS, M. I. F. Taphonomic analysis on Neogene ostracods from Solim\u00f5es formation, Borehole 1AS-5-AM, Brazil: A tool to the paleoenvironmental reconstitution<\/a>. Journal of South American Earth Sciences<\/strong>. vol. 122, 104172. dec. 2022.
\n<\/strong>SACEK, V. et al<\/em>. The Amazon paleoenvironment resulted from geodynamic, climate, and sea-level interactions<\/a>. Earth and Planetary Science Letters. <\/strong>vol. 605, 118033. mar. 1, 2023.<\/p>\n","protected":false},"excerpt":{"rendered":"Fossils of marine microorganisms indicate that Caribbean waters inundated the Solim\u00f5es basin at least 11 times over the last 23 million years","protected":false},"author":545,"featured_media":492339,"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":[206,200,231,240,252],"coauthors":[1498],"class_list":["post-492338","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science","tag-biodiversity","tag-environment","tag-evolution","tag-geology","tag-oceanography"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/492338","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\/545"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=492338"}],"version-history":[{"count":5,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/492338\/revisions"}],"predecessor-version":[{"id":498923,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/492338\/revisions\/498923"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media\/492339"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=492338"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=492338"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=492338"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=492338"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}