New occurrence of sirenians in the Pirabas Formation (Miocene), Pará, Brazil

Palaeoenvironment of the Miocene Pirabas Formation mixed carbonate–siliciclastic deposits, Northern Brazil: Insights from skeletal assemblages

Palaeontological framework from Pirabas Formation (North Brazil) used as potential model for equatorial carbonate platform

The genus Perissocytheridea Stephenson, 1938 (Crustacea: Ostracoda) and evidence of brackish water facies along the Oligo-Miocene, Pirabas Formation, eastern Amazonia, Brazil

The faunas of the highly fossiliferous Pirabas Formation belong to the southern part of the biogeographical unit known as "Neogene Tropical America".This unit developed prior to the closure of the Central American Seaway by the Isthmus of Panama.Until now, the age of the Pirabas Formation was inferred only from biostratigraphy.The Sr-isotope ( 87 Sr/ 86 Sr) values of pectinid shells from the Pirabas Formation show that most parts of this unit were deposited during the Late Burdigalian (about 16-17 Ma ).This result does not contradict biostratigraphic data and it constrains the age of the Pirabas Formation more tightly than do previous estimates of age, it for future, more precise biogeographical comparisons.

Biostratigraphy and paleoenvironment correlation based on benthic foraminifera from the cenozoic Marajó and Pirabas formations, Eastern Amazon Coast, Brazil

The Neogene Tropical Western Central Atlantic-South American faunal assemblage from the Pirabas Formation (Early Miocene) has specific and unique features, which distinguishes it from the rest of the Proto-Caribbean Subprovince in diversity, paleoceanographic condition and ecosystems. Principal component analysis (PCA) distinguished three groups of localities with similar faunas (Group A: Ilha de Fortaleza, Colônia Pedro Teixeira and Praia de Fortalezinha; Group B: Estação Agronômica, Ilha de Marajó, Turiacu, Baixo Parnaíba, Aricuru and Salinópolis; Group C: Capanema B-17 Mine) and five different depositional facies (surf zone, beach, lagoons, tidal channel and tidal delta), in agreement with previous geological studies showing heterogeneous paleoenvironments among the outcrops. These heterogeneous lithostratigraphic sequences suggest different members, and may be related to different ages along the Pirabas sequence. The Neogene Northwestern Atlantic Subprovince is erected to encompass this entire geographical area.

This work deals the analysis of the Historical Biogeography of the brazilian cenozoic paleocarcinofauna, recorded in the Maria Farinha, Tremembé and Pirabas formations. This taxa has affinity with the tethian carcinofaunas and modern aspect. The paleobiogeographic setting allows to situate their biological events of the origin, dispersional and irradiation trends in the tethian, south high latitude and amphitropical origins. The majority of the brazilian carcinofauna has affinity with the tethian faune, that migrate in two seaways, west and east. The phylogenetic relationships suggest appearence of the Thalassinoidea group from the Caridea infraordo. The Retroplumidae family (genus Costacopluma) recorded at Maria Farinha Formation is directed related with the cenozoic ocypodid (i.e. genus Uca at Pirabas Formation, living in the same ecological niches and environmental tolerances. Also, the morphological similarities between Xanthoidea and Portunoidea in the Paleocene, suggest monophyletic relationships with Goneplacidae and Hexapodidae. The detailed phylogenetic studies in Goneplacidae family reveals that Glyphithyreus genus is related with Eucratopsinae subfamily.

Brazilian Miocene crabs II. A new genus and species (Crustacea: Decapoda: Brachyura) from Pirabas Formation, northern Brazil

X-ray micro-computed tomography of burrow-related porosity and permeability in shallow-marine equatorial carbonates: A case study from the Miocene Pirabas Formation, Brazil

The chondrichthyan fauna from the Pirabas Formation is redescribed.Only thirteen nominal taxa are considered valid. From these taxa, ten were reassigned to extant taxa (Carcharhinus sorrah, Carcharhinus perezii,Galeocerdo cuvier, Rhizoprionodon lalandii, Sphyrna sp., Hemipristis elongatus, Carcharodon carcharias, Isurus oxyrinchus, Nebrius ferrugineus, and indeterminate Myliobatidae), confirming the Neogene age of this formation. This elasmofauna is compared with other Caribbean and African Tertiary faunas.

The Pirabas Formation, a representative geological unit of the Brazilian marine Cenozoic, assembles a rich and diverse fossil record, which includes Comatulida crinoids, components of the faunal assembly of the Pirabas Sea. Samples from the B-17 Mine outcropping, Municipality of Capanema, and the Atalaia Beach, Municipality of Salinópolis, Pará State were analyzed, and hundreds of disarticulated ossicles of crinoid comatulids were found. Centrodorsals of crinoids of the species Sievertsella polonica Radwanska, Discometra rhodanica (Fontannes), of the genus Kiimetra Shibata & Oji, and the family ?Zygometridae were herein identified. The taxa have affinities with those already recorded in the Miocene of the Caribbean biogeographic province and are consistent with the faunal interchange that has existed between the Tropical East Pacific and the Tropical West Atlantic regions. The material suggests the Pirabas Sea as a center of origin for some taxa, while also strengthening possible connections from the Atlantic to the Central Paratethys, the Mediterranean, and the Indian Ocean. Keywords: Pirabas Sea, Cenozoic, Miocene, echinoderms, crinoids, paleobiogeography.

Paleontological study of the Oligocene/Miocene boundary in the Ilha de Santana and Pirabas formations, Pará-Maranhão Basin on the Northwest equatorial platform of Brazil

Miocene heterozoan carbonate systems from the western Atlantic equatorial margin in South America: The Pirabas formation

First evidence of fossil snapping shrimps (Alpheidae) in the Neotropical region, with a checklist of the fossil caridean shrimps from the Cenozoic

Estudos geológicos e geofísicos baseados na técnica de investigação Sondagem Elétrica Vertical (SEV) foram utilizados na identificação de litofácies de origem tectônica dos depósitos neógenos carbonáticos e siliciclásticos, correspondentes as Formações Pirabas e Barreiras, e sedimentos da unidade Pós-Barreiras, que constituem o preenchimento da Plataforma Bragantina, nos municípios de Capanema e Primavera, região continental do nordeste do estado do Pará. Os dados de resistividade aparente das sondagens elétricas foram processadas utilizando o programa IPI2win, que é projetado para realizar inversões 1D automáticas, correlacionando-as sempre que possível com os perfis litológicos de poços, disponíveis na plataforma online do Sistema de Informação de Águas Subterrâneas (SIAGAS), com o intuito de ajustar os valores de espessuras das camadas (fornecidas pelos perfis ) com a solução do modelo geoelétrico e estimando-se as resistividades de cada camada de acordo com a composição mineralógica descrita nos poços. Os resultados das sondagens elétricas realizadas neste trabalho mostraram-se satisfatórias, pois permitiram diferenciar o possível contato entre a Formação Pirabas com o embasamento cristalino a uma profundidade em torno de 50 metros no município de Capanema, devido o forte contraste de resistividade, no município de Primavera diferenciou as Formações Pirabas e Barreiras, em torno de 9 metros de profundidade.
 Palavras-chave: Sondagem Elétrica Vertical (SEV). Neógeno. Nordeste do Estado do Pará.