CLINOFORM MORFOLOGIES IN THE SOUTHERN BRAZILIAN CONTINENTAL MARGIN: CURRENTS AND DELTAIC PROCESSES IMPACTS ON CONTINENTAL MARGINS FORMATION SINCE NEOGENE

Abstract

The expansion of continental platforms on passive margins is a topic of debate until today. Some authors argue that the accretion of the continental shelf occurs mainly through the advancement/progradation of fluvial depositional systems over the platform during intervals of relative sea level fall, while others consider the action of marine currents as the main transport agent for deposition and margin expansion. These processes are recorded in marine stratigraphy in the form of depositional clinoforms. Clinoforms are sedimentary layers that record the seabed surface morfology during geological intervals of continental shelf expansion. Thus, by measuring geometric parameters of clinoforms, it is possible to classify them morphologically in time and space. This classification allows then to identify and interpret the oceanographic and geological processes responsible for the formation of clinoforms, since each morphological pattern is associated with a different depositional context. In this context, the present work aims to test if the dominant factor in the formation of the South Brazilian margin since the Neogene is marine currents or fluvial processes, through quantitative and qualitative analysis of the clinoforms. For this, 2D and 3D seismic data from the Santos and Pelotas basins were acquired by the ANP (National Petroleum Agency), which have great potential for this type of study, since there is an intense action of marine currents and also the presence of river systems on the platform. This data will be interpreted using the IHS Kingdom Suite Software, where the geometric parameters will be measured and then compiled and processed in Python for the classification and interpretation of clinoform's type. In this way, an interpretative model of the South Brazilian continental margin evolution and of the dominant processes in this formation will be created. This model will identify regions where deltas and river channels were formed during periods of continental shelf accretion. The presence of river channels buried in the continental shelf is an important geological risk for the installation of offshore wind farms, and the Pelotas Basin has been a focus of interest for this nascent industry.Furthermore, this study will be relevant for understanding the processes that form continental margins in a more comprehensive way, as it will represent an important case study for a global problem.