Banca de DEFESA: Flávia Araújo de Arruda Cabral

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Flávia Araújo de Arruda Cabral
DATE: 28/07/2022
TIME: 14:30
LOCAL: Remotamente
TITLE:
KEY WORDS:

Sergipe-Alagoas Basin; Morro do Chaves Formation; Coquinas; Geochemistry; Stable isotopes

PAGES: 173
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

The lithostratigraphic unit of interest in this work is the neobarremian to eoaptian Morro do Chaves Formation (Jiquiá Stage), from the rift phase of the Sergipe-Alagoas Basin, characterized by calcarenites and calcirrudites intercalated with claystones, shales, sandstones and conglomerates. The coquinas (bioclastic limestones) of the Morro do Chaves Formation represent an important case study because are analogous rocks of pre-salt reservoirs. In this work, carbonate rocks and calciferous sandstones with bioclasts are highlighted. Petrographically, carbonate rocks have a calcitic composition, with large amounts of bivalve mollusks and ostracods in smaller proportions, and may have siliciclastic grains. According to Dunhan (1962), these rocks were classified as wackestones, packstones and grainstones and according to Embry and Klovan (1971) as rudstones. Diagenetic processes such as neomorphism, micritization, dissolution, cementation, pyritization and mechanical and chemical compaction were observed in these rocks. From geochemical analysis it was possible to verify that SiO2, TiO2, Al2O3, MgO and K2O come from the detrital fraction and also from clay minerals, while CaO is representing the chemical fraction represented by calcite. Chemical analysis performed on limestones show that CaO (30.32 to 58.03%) occurs as the main constituent, followed by SiO2 (<0.001 to 37.78%), while TiO2, Al2O3, Fe2O3, MnO, MgO, Na2O, K2O, P2O5, Rb and Sr occur as minor and trace constituents. The magnesium content in these carbonate rocks is very low, showing that was no dolomitization process and that the calcites have a low magnesium content. XRD analysis showed the low occurrence of clay minerals kaolinite, kaolinite 2M (dickite) and montmorillonite. Carbon and oxygen isotopes were analysed in the samples of the outcrop of the Atoll Quarry, whose δ13C values ranged from -5.34 to -3.67‰ and the δ18O values ranged from -8.56 to -4.13‰ VPDB typical of freshwater lacustrine environments. From the correlation or non-correlation of the isotopic values, it was possible to verify both closed hydrological and open hydrological behavior in the lake that gave rise to these rocks. The calculated salinity values range from 112.56 to 117.73 and confirm a freshwater environment for the formation of this rocks. The calculated values paleotemperature ranged from 8.4 to 17.4°C showing that was few fluctuations in temperatures in the lake in that period. The study of ostracods allowed the identification of species from four non-marine genera Cypridea Bosquet, 1852, Reconcavona Krömmelbein, 1962, Theriosynoecum Branson, 1936 and Petrobrasia Krommelbein, 1965, corroborating with the lacustrine environment of the Morro do Chaves Formation. Furthermore, from the occurrence of Cypridea riojoanensis Moura, 1972, it was possible to establish the biochronostratigraphic positioning of the outcrop of the Morro do Chaves Formation, in Propriá-SE, in the Jiquiá Stage (Barremian-Aptian).

BANKING MEMBERS:
Presidente - 1133907 - VIRGINIO HENRIQUE DE MIRANDA LOPES NEUMANN
Interno - 3089741 - CLAUS FALLGATTER
Interno - 1474289 - GELSON LUIS FAMBRINI
Externa à Instituição - VALÉRIA CENTURION CÓRDOBA - UFRN
Externo à Instituição - VICTOR HUGO SANTOS - UENF