Neogene Carbonate processes on southern Brazilian margin

• Grant number: 25/09571-8
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: November 01, 2025
• End date: October 31, 2026
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geophysics
• Principal Investigator: Luigi Jovane
• Grantee: Mateus Alexander Campeche Gama
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The Brazilian continental shelf, one of the most extensive on the planet, remained relatively stable throughout the Cenozoic, becoming a natural laboratory for the study of carbonate platforms. This scenario enables the investigation of global climatic variations, such as changes in sea level and temperature, as well as geometric transitions of the platforms. Studies in Marine Geology and data surveys from the Petroleum Industry have been fundamental for the exploration of potential reservoirs, the analysis of geomorphology, and the paleoenvironmental evolution of these carbonate platforms. Carbonate platforms have been widely studied during the Neogene as it was the main propagation period during the Cenozoic. These studies focus on the North and Central Atlantic, the Mediterranean Sea, and the Indo-Pacific. However, there are still gaps in knowledge regarding their evolution in the South Atlantic, especially considering their vast extent and the impacts of paleoenvironmental factors such as global warming. Understanding the responses of Brazilian platforms to global climate changes is, therefore, essential. This study focuses on two areas: the Santos Basin and the Besnard Bank, addressing three distinct time scales. The Santos Basin, Brazil's main oil-producing region, is analyzed in the first chapter regarding the evolution of tropical carbonate platforms from the late Oligocene to the Quaternary. In the third chapter, variations in seismic facies are analyzed to investigate the formation of a buildup in the northern part of the basin, using high-resolution data covering the period since the Last Glacial Maximum. The second chapter deals with the Besnard Bank, part of the Vitória-Trindade Chain, an active volcanic region during the Miocene and close to the Abrolhos Bank, one of the largest modern carbonate platforms in the South Atlantic. The Besnard Bank began to form in the Eocene and persists to the present day. The research employed conventional seismic data (2D and 3D) from the petroleum industry, high-resolution seismic data, and well information (lithology and check-shot) to evaluate the stratigraphy of the platforms. The results indicate that tropical platforms in the South Atlantic, located at approximately 30° S, began to form in the early Miocene. These platforms underwent a geometric transition, evolving from an Isolated Carbonate Platform to a Rimmed Shelf during the aggradational-progradational phase. In the Quaternary, they were drowned due to intense global climate changes. At Besnard Bank, the carbonate platform evolved from aggradational to progradational during the Miocene, a period in which intense dolomitization occurred, associated with fluid escape zones identified in seismic sections. The buildup studied in the Santos Basin was identified in conventional 2D seismic sections and detailed in high-resolution sections. In these images, a pattern of blank reflectors was observed below the buildup, along with a high-amplitude anomaly parallel to these dimmed reflectors. The results demonstrate that South Atlantic carbonate platforms were influenced by both local and global factors, highlighting the importance of seismic investigation with multiple methodologies to detail the evolutionary processes shaping the geometry of these platforms. (AU)