Bivalves Bakevelliidae da Formação Romualdo (Andar Alagoas, Cretáceo Inferior), Bacia do Araripe, NE Brasil: significado paleoambiental e paleogeográfico
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Data
2020-05-15
Autores
Rodrigues, Mariza Gomes
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Universidade Estadual Paulista (Unesp)
Resumo
Bakevelliidae (Bivalvia, Pterioidea) são bivalves extintos, marinhos, de epifauna a semiinfauna, bissados, suspensívoros, com pelo menos 20 gêneros descritos e inúmeras ocorrências em todo o mundo. Eles prosperaram do Paleozoico tardio ao Eoceno, atingindo máxima diversidade durante o Mesozoico (principalmente no Jurássico Inferior e Médio). Eles também foram abundantes e bem distribuídos em sucessões sedimentares cretáceas, como àquelas das bacias do Araripe e Sergipe-Alagoas, ocorrendo também de forma pontual na bacia de Pernambuco-Paraíba, no nordeste do Brasil. Neste documento, novos Bakevelliidae aptianos (Cretáceo Inferior) são descritos para a Formação Romualdo, Grupo Santana, Bacia do Araripe, nordeste do Brasil. A análise está fundamentada no exame detalhado de 361 espécimes, provenientes do terço superior da Formação Romualdo, principalmente das seções geológicas nas bordas sudoeste e sudeste da bacia, tendo sido, porém, registrados em toda a Bacia do Araripe. Juntamente com outros membros conhecidos da família Bakevelliidae, já registrados na Formação Romualdo (i.e., Aguileria dissita), os novos bivalves (Araripevellia musculosa gen. et sp. nov., Aguileria romualdoensis sp. nov. e Gen et sp. Indet.) indicam que a fauna de Bakevelliidae desta unidade foi mais diversa do que se imaginava anteriormente. Calcários ricos em conchas de Bakevelliidae, alguns com espécimes preservados in situ, estão restritos ao terço superior desta unidade, o mesmo intervalo estratigráfico contendo calcários com equinodermos, gastrópodes e estromatólitos. Esses bivalves pteriomorfos, portanto, são um testemunho do breve “Mar de Bakevelliidae” que inundou toda a Bacia do Araripe, durante o Aptiano. Análises paleoautoecológicas indicam que Araripevellia musculosa gen. et sp. nov. era uma espécie de epifauna, que viveu em substratos bioclásticos e estáveis, enquanto Aguileria romualdoensis sp. nov. era uma forma semi-infaunal bissada, que colonizou sedimentos finos. Espécimes das três espécies de Bakevelliidae estudadas são encontrados juntos em uma dada concentração fóssil, mas apenas Araripevellia musculosa gen. et sp. nov. é preservada in situ. Esta espécie é registrada, principalmente, em concentrações fósseis primariamente biogênicas, formando delgados depósitos de sufocamento. Notavelmente, Aguileria romualdoensis sp. nov. se assemelha a A. renauxiana da Formação Woodbine, Cenomaniano, Texas, EUA. Além disso, Aguileria dissita também é registrada na Formação Riachuelo, Aptiano tardio-Albiano, da Bacia de Sergipe-Alagoas. Juntamente com outros macroinvertebrados (i.e., gastrópodes, equinodermos, bivalves), a fauna de Bakevelliidae da Formação Romualdo é fortemente biocorrelata à da Formação Riachuelo, suportando um cenário paleogeográfico em que águas marinhas inundaram a Bacia do Araripe advindas de sudeste, provavelmente através das bacias do Recôncavo-Tucano-Jatobá. Finalmente, informações sedimentológicas, estratigráficas e paleontológicas indicam que o desaparecimento dos Bakevelliidae na Formação Romualdo está vinculado a continentalização da Bacia do Araripe.
Bakevelliids (Bivalvia, Pterioidea) are extinct, marine, stationary epifaunal to semi-infaunal, suspension feeding bivalves with at least 20 described genera and numerous occurrences worldwide. They thrived from the Late Paleozoic to Eocene, reaching the maximum diversity during the Mesozoic (mainly Early and Middle Jurassic). They were also abundant and widespread in many Cretaceous sedimentary successions, as in the Araripe and Sergipe- Alagoas basins, also occurring occasionally in Pernambuco-Paraíba basin, in NE Brazil. In this document, new Aptian (Lower Cretaceous) bakevelliid bivalves are described for the Romualdo Formation, Santana Group, Araripe Basin, northeastern Brazil. Analysis is based on the detailed examination of 361 specimens all from the upper third interval of the Romualdo Formation, mainly from geological sections in the southwestern and southeastern borders of the basin, but they were recorded in all four corners of the Araripe Basin. Together with the other known members of the family Bakevelliidae, already record in the unit (i.e., Aguileria dissita), the new bivalves (Araripevellia musculosa gen. et sp. nov., Aguileria romualdoensis sp. nov., and Gen et sp. indet.) indicate that the Romualdo bakevelliid fauna was more diverse than previously realized. Bakevelliid-rich carbonates, some with in situ specimens, are restrict to the upper third of this unit, the same stratigraphic interval yielding echinoderm-, gastropod- and stromatolitebearing limestones. These pteriomorphian bivalves were widely distributed in the Romualdo Formation and are a testimony of the short-lived bakevelliid-sea that flooded the whole Araripe Basin, during the Aptian. Paleoautoecologic analysis indicate that Araripevellia musculosa gen. et sp. nov. was an epifaunal, byssate species, living in bioclastic, stable substrates, whereas Aguileria romualdoensis sp. nov. was a semi-infaunal, byssate form. Specimens of the three studied bakevelliid species can be recorded all together in a given fossil concentration, but only Araripevellia musculosa gen. et sp. nov. is found in situ. This species is found in primarily biogenic fossil concentrations forming thin obrution deposits. Notably, Aguileria romualdoensis sp. nov. close resembles A. renauxiana from the Cenomanian Woodbine Formation, Texas, US. In addition, Aguileria dissita is also recorded in the Late Aptian-Albian Riachuelo Formation of the Sergipe-Alagoas Basin. Together with other macroinvertebrates (i.e., gastropods, echinoderms, bivalves) the bakevelliid fauna of the Romualdo Formation can be biocorrelated tightly with that of the Riachuelo Formation, supporting a paleogeographic scenario with the marine waters flooding the Araripe Basin from the southeast, probably via Recôncavo-Tucano-Jatobá Basin system. Finally, sedimentologic, stratigraphic and paleontological information indicate that the fate of the bakevelliids in the Romualdo Formation, is bound up with the onset of continentalization of the Araripe Basin.
Bakevelliids (Bivalvia, Pterioidea) are extinct, marine, stationary epifaunal to semi-infaunal, suspension feeding bivalves with at least 20 described genera and numerous occurrences worldwide. They thrived from the Late Paleozoic to Eocene, reaching the maximum diversity during the Mesozoic (mainly Early and Middle Jurassic). They were also abundant and widespread in many Cretaceous sedimentary successions, as in the Araripe and Sergipe- Alagoas basins, also occurring occasionally in Pernambuco-Paraíba basin, in NE Brazil. In this document, new Aptian (Lower Cretaceous) bakevelliid bivalves are described for the Romualdo Formation, Santana Group, Araripe Basin, northeastern Brazil. Analysis is based on the detailed examination of 361 specimens all from the upper third interval of the Romualdo Formation, mainly from geological sections in the southwestern and southeastern borders of the basin, but they were recorded in all four corners of the Araripe Basin. Together with the other known members of the family Bakevelliidae, already record in the unit (i.e., Aguileria dissita), the new bivalves (Araripevellia musculosa gen. et sp. nov., Aguileria romualdoensis sp. nov., and Gen et sp. indet.) indicate that the Romualdo bakevelliid fauna was more diverse than previously realized. Bakevelliid-rich carbonates, some with in situ specimens, are restrict to the upper third of this unit, the same stratigraphic interval yielding echinoderm-, gastropod- and stromatolitebearing limestones. These pteriomorphian bivalves were widely distributed in the Romualdo Formation and are a testimony of the short-lived bakevelliid-sea that flooded the whole Araripe Basin, during the Aptian. Paleoautoecologic analysis indicate that Araripevellia musculosa gen. et sp. nov. was an epifaunal, byssate species, living in bioclastic, stable substrates, whereas Aguileria romualdoensis sp. nov. was a semi-infaunal, byssate form. Specimens of the three studied bakevelliid species can be recorded all together in a given fossil concentration, but only Araripevellia musculosa gen. et sp. nov. is found in situ. This species is found in primarily biogenic fossil concentrations forming thin obrution deposits. Notably, Aguileria romualdoensis sp. nov. close resembles A. renauxiana from the Cenomanian Woodbine Formation, Texas, US. In addition, Aguileria dissita is also recorded in the Late Aptian-Albian Riachuelo Formation of the Sergipe-Alagoas Basin. Together with other macroinvertebrates (i.e., gastropods, echinoderms, bivalves) the bakevelliid fauna of the Romualdo Formation can be biocorrelated tightly with that of the Riachuelo Formation, supporting a paleogeographic scenario with the marine waters flooding the Araripe Basin from the southeast, probably via Recôncavo-Tucano-Jatobá Basin system. Finally, sedimentologic, stratigraphic and paleontological information indicate that the fate of the bakevelliids in the Romualdo Formation, is bound up with the onset of continentalization of the Araripe Basin.
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Sistemática, Bivalves pteriomorfos, Aptiano, Grupo Santana, Biocorrelação, Tafonomia, Mar epicontinental, Systematics, Pteriomorphian bivalves, Aptian, Santana Group, Biocorrelationen, Taphonomy, Epicontinental sea