Banca de QUALIFICAÇÃO: ANA KAROLINY ALVES DE MEDEIROS

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : ANA KAROLINY ALVES DE MEDEIROS
DATE: 25/08/2023
TIME: 14:00
LOCAL: videoconferência https://www.youtube.com/@ppggufrn
TITLE:

Upper Cretaceous sequence stratigraphy and isotopic of Barreirinhas and Pará-Maranhão basins, Brazilian Equatorial Margin

KEY WORDS:

Brazilian Equatorial Margin, Barreirinhas Basin, Pará-Maranhão Basin, Upper Cretaceous, Isotopic stratigraphy.

PAGES: 40
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

The Brazilian Equatorial Margin (BEM) comprises a region of new hydrocarbon exploration frontier. The detailed knowledge of its evolution, tectonic processes and stratigraphic slicing, although still poorly developed, is fundamental for the determination of its petroleum potential. In this context, the present research aims to elaborate a paleoreconstitution of the time slice corresponding to the Upper Cretaceous of the Barreirinhas and Pará-Maranhão basins, located and inserted in the tectono-stratigraphic context of the MEB. For this, results of isotopic analysis with emphasis on stable isotopes of Carbon and Oxygen were used supported by the stratigraphic interpretation of well data (1D) and 2D and 3D seismic surveys. The integration of these data in the study of the evolution of the BEM is relevant because isotopic stratigraphy (subarea of Chemostratigraphy) is a method of stratigraphic analysis characterized by good sensitivity to paleoenvironmental variations, showing itself applicable in the face of possible failures, absences and/or limitations of conventional methods. The analysis of the Upper Cretaceous in the 1D data integrated with the seismic analysis allowed the individualization of 5 depositional sequences composing this interval. The first one, called D1 Sequence, begins at the Break-up Unconformity and extends to the Cenomanian Unconformity, and can be subdivided into two other higher-order sequences, D1A and D1B. The most basal sequence (D1) is characterized by an isotopic signature compatible with periods of higher organic productivity, warmer temperatures and lower potential for preservation of organic matter. Sequence D2, younger, goes from the Cenomanian Unconformity to the Turonian Unconformity, standing out from the others for presenting the most positive isotopic signature among the entire study interval. It is in this sequence that the samples with the most enriched results in the heavy isotope are found and, therefore, present a possible greater potential for preservation of organic matter. Still in D2 Sequence, at approximately 1050m, the most important anoxic event of this time slice is interpreted. Like the global anoxic event recognized and mapped by Jenkyns (2010), this event occurs precisely between the end of the Cenomanian and the beginning of the Turonian, called OAE-2 (Oceanic Anoxic Event-2). Therefore, it can be concluded that within the D2 Sequence there is an Marine Flooding Surface (MFS), well marked and identified in 1D data with the aid of the δ13C ‰ (V-PDB) isotope ratio variation curve in the shales. Lithostratigraphically, this interval also corresponds to the deposition of the Travosas Formation, represented by shales with intercalation of Areinhas Formation sandstones, which may therefore corroborate a more favorable interval for reservoir rocks mainly in the form of turbidite deposits. The next sequence, named D3, occurs from the Turonian Unconformity to the Campanian Unconformity. It is characterized by isotopic behavior compatible with negative excursions of δ13C ‰ (V-PDB) at the sequence bottom, which vary towards the top until they become more enriched values. Thus, it is towards the top that this sequence begins to show a better trend of organic matter preservation, where another important MFS can also be identified. Going from the Campanian Unconformity to the Maastrichtian Unconformity, D4 Sequence maintains the trend of D3 Sequence of increasing the potential for preservation of organic matter progressively towards its upper limit, becoming more positive, and ending with a drop in these values. Finally, D5 Depositional Sequence marks the transition from the Cretaceous to the Palaeogene Period, presenting an isotopic signature compatible with a drop in organic productivity and organic matter preservation potential, followed by cooling temperatures as a reflection of global variations.

COMMITTEE MEMBERS:
Presidente - 1149363 - VALERIA CENTURION CORDOBA
Externo ao Programa - 1755591 - CARLOS CESAR NASCIMENTO DA SILVA - UFRNExterna ao Programa - 277437 - MARCELA MARQUES VIEIRA - UFRNExterna à Instituição - LILIANE RABELO CRUZ - PETROBRAS