Banca de DEFESA: Daniele de Melo Mendes Britto

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Daniele de Melo Mendes Britto
DATE: 30/05/2022
TIME: 14:00
LOCAL: Remotamente
TITLE:
KEY WORDS:

Ostracoda; taxonomy; pyritization; Rio da Serra Stage; Aratu Stage

PAGES: 107
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

The advancement of studies addressing biostratigraphy based on ostracods has shown an effective contribution of this microfossil group to the knowledge of the geological history of the basins of Northeast Brazil. The biostratigraphic results obtained through the study of non-marine ostracods in the Recôncavo Basin were decisive in the Mesozoic chronostratigraphic characterization of Brazilian basins. In addition to age calibration, the recognition of the local stage of the Recôncavo Series has allowed stratigraphic and faunal correlations in several interior basins of Brazil. In this context, the present work aimed to analyze non-marine ostracods from Rio da Serra Stage (Berriasian–Hauterivian) and Aratu Stage (Hauterivian–Barremian), recovered from the Maracangalha Formation, Recôncavo Basin. The sample preparation methodology followed the usual procedures for the recovery of carbonate microfossils in shales and siltstones along the Gameleira and Manguinhos profiles (Ilha de Itaparica) and Praia da Falha (Ilha dos Frades) Baía de Todos os Santos. Scanning Electron Microscopy and Energy Dispersive Spectrometry sessions were carried out to detail morphological features of the carapaces, as well as the mineral habit of pyrites and the punctual identification of chemical elements in the carapaces of ostracods. In the analyzed material, seven species of the genus Cypridea Bosquet, 1852; two species of Reconcavona Krömmelbein, 1962; three species of Ilhasina Krömmelbein, 1963; one species of Candona Baird, 1945; one species of Brasacypris Krömmelbein, 1965 and one species of the genus Alicenula Rossetti & Martens, 1998. The ostracod association found was interpreted as typical of a lacustrine environment. The biochronostratigraphic positioning in Rio da Serra Stage (Berriasian–Valanginian), subzone RT-004.2, was possible by the recognizing of the guide species Reconcavona? polita Viana, 1966, in the Manguinhos outcrop. In the Praia da Falha outcrop, the faunal association pointed an age between the Rio da Serra and Aratu stages (Valanginian–Hauterivian), through the record of the species Ilhasina amphotera and Cypridea lunula. In the Gameleira outcrop, the age interpretations were inconclusive, due to the rarity and preservation of the microfossiliferous assemblage. The preservation pattern of the ostracods carapaces varied according to the change of sedimentary facies, which implied in ostracods with total or partial replacement of the carapaces by pyrite. The results of the EDS analyzes indicated the presence of Fe and S, corroborating iron sulphide mineralization. The SEM images revealed the euhedral and framboidal habit of the pyrites in the carapaces, which indicate conditions of early diagenesis and low burial depths.

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