Navegando por Assunto "Paleontologia"

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Acesso aberto (Open Access)
Geologia e paleontologia do biohermito da Formação Pirabas (Mioceno Inferior)
(2013-09) TÁVORA, Vladimir de Araújo; NOGUEIRA NETO, Ignácio de Loiola Alvares; MACIEL, Lidiane Medeiros
This work concerns with the detailed geological and paleontological study of the reef facies of the Pirabas Formation, that outcrop at the Maçarico beach, of Salinópolis district, Pará State, as a small, isolated and lenticular sedimentary bodie developed in the inner platform inner ramp of the Pirabas Sea. The biotic constituents are diverse and composed by three groups of coralline algae, sponges, corals, bryozoans, echinoids, foraminifera, ostracodes and molluscs. Three stages of the ecologic sucession were recognized in this patch reef: stabilization, colonization and diversification. Thin micritic crusts, recognized at top of the beds in diversification stage suggest the degradation of the environmental conditions favorable to reef accretion probably due to continentalization of the depositional site. The petrographic investigation reveals only one, homogeneous depositional microfacies, named biomicrite, without compositional and textural changes. The marine cementation is represented by microcrystalline agglomerates and micritic cement, locally neomorphosed to biosparite and detrital carbonatic components of the unconsolidated biogenic debris, resulted from the disintegration of the aragonite from the algalic remains accumulated as micritic mud. In the construction of the reef framework the red macroalgae were fundamental to the lithification and building of the framework, and very important to the protection and cementation of the others constituents.
Acesso aberto (Open Access)
Ictiólitos da Formação Pirabas, mioceno do Pará, Brasil, e suas implicações paleoecológicas
(Universidade Federal do Pará, 2011-06-01) COSTA, Sue Anne Regina Ferreira da; RICHTER, Martha; http://lattes.cnpq.br/9381228195500524; ROSSETTI, Dilce de Fátima; http://lattes.cnpq.br/0307721738107549
The Pirabas Formation (Oligo-miocine), which is represented by carbonates deposits through the Brazilian Coastal Area between the States of Pará and Piauí, is recognized for its fossil richness. Among the many fossils paleoichthyofauna stands out for its abundance in outcrops, but the absence of stratigraphic and facies control of these fossil restricted their potential use in paleoenvironmental interpretations. The joint use of the technique of wet sieving for the recovery of ichthyoliths and microfacies and facies analysis of sediments taken from Pirabas Formation deposits, which were exposed in the B17 mine (Capanema-PA), allowed for the first time the use of vertebrate fossil for the elaboration of an interdisciplinary paleoenvironmental reconstruction model. The 3594 recovered ichthyoliths, along with the 5 facies associations and the 4 carbonate microfacies, led to the conclusion that these deposits of Pirabas Formation were formed in marine-marginal depositional system, with different environments genetically associated as shore face (surf zone), beach, lagoon, tidal channel and tidal delta, which would be part of an estuarine system with the influence of wave, marked by four different depositional cycles related to possible transgressiveregressive episodes. The estuarine environment was confirmed by the assembly of ichthyoliths, observing that this assembly is formed by both freshwater specimens, represented by the Characidae family, an unheard occurrence for the unit until then, as for marine specimens, for example, the sharks. Several dental types, possibly attributed to representatives of brackish waters, such as the genera Dasyatis and Sarpa, both equally registered for the first time, also strengthens the proposed environment. The distribution of the ichthyological community evidences palaeoenvironmental control, having registered their highest abundance in deposits of tidal channel. However, the influence of relative sea level resulted in the development of transgressive-regressive depositional cycles, which also exerted strong control on the stratigraphic distribution of the B17 Mine registered ichthyoliths, reinforcing the importance of interdisciplinary studies in refining palaeoecological reconstruction of this unit.
Acesso aberto (Open Access)
A natureza complexa do patrimônio paleontológico da praia do Atalaia, munícipio de Salinópolis, Pará, Amazônia Oriental, Brasil
(Universidade Federal do Pará, 2021-09-02) SILVA, Rayana Alexandra Sousa da; COSTA, Sue Anne Regina Ferreira da; http://lattes.cnpq.br/3629751361208856; https://orcid.org/0000-0002-3314-5148
In this research, we reflect on Paleontological Heritage as a specifically complex heritage category that is inserted in environmental, cultural and mineral policies. The analysis starts from a review of the transformations in the conceptions of cultural and natural heritage in Brazil, to problematize the various dimensions that interfere in the processes of heritage patrimonialization, besides contextualizing and reinforcing its social importance in a context of great complexity. We will look specifically at the paleontological heritage of Atalaia Beach, which is one of the main beach resorts in the state of Pará, receiving tourists from all over Brazil and the world every year. The region's patrimony is formed by an expressive fossil record from the Brazilian marine Cenozoic, dating from 23 to 25 m.y., representing the transgressive moment of advance and retreat of the Atlantic Ocean over the continent. The fossils found are mainly of marine invertebrates and vertebrates, such as manatees, rays, sharks, gastropods and fishes. Thus, the main objective of this work is to investigate and analyze the paleontological heritage of Atalaia Beach, seeking to relate and communicate among themselves the subjects, environmental context and cultural heritage. To this end, based on Morin, in the method that seeks complexity through the creation of avenues of approach, we carried out observations in different pheres: a public hearing for environmental licensing, an activity with elementary school teachers and an interview with a private collector of fossils. The results presented in the form of two articles point out that a) the use of this heritage follows a utilitarian logic of nature transformation; b) we highlight a complex network of environmental, economic and social issues that must be considered when any project of valorization, education or even of analysis of the paleontological heritage of Atalaia Beach is intended; c) we point out the urgent need to transform our practices in relation to paleontological heritage, so that we can think and act upon it in a more comprehensive way, conceiving it as a fundamental right which contributes to the full exercise of citizenship.