SEISMIC STRATIGRAPHY OF CEARÁ PLATEAU AND ADJACENT BASINS, BRAZILIAN EQUATORIAL MARGIN
Ceará Plateau; Brazilian Equatorial Margin; Drowned reef
The Brazilian Equatorial Margin (MEB) is one of the largest and less known in the world. Over the years, the MEB studies have focused on the continental shelf, driven by the oil and gas industry interest. However, there is a great lack of information about the deep sea. Deep sea sedimentary deposits have been shown as important not only for paleoceanographic reconstructions, but also as potential source of hydrocarbons. The Ceará Plateau is a prominent feature of the MEB. It is located 100 km off the coast of Fortaleza/CE, between 200 m (top) and 1600 m (base) depths. Between Ceará Plateau (PtC) and the slope stricto sensu occurs the formation of a semi-confined basin, in deep water, called in this work of Ceará Trough. Both features are located east of the Alto de Fortaleza, therefore, still in the tectono-sedimentary context of the Potiguar Basin. The aim of this research is the characterization of PtC tectonic and geological context, trying to understand the evolution of this MEB part. In addition, this work also aims to provide subsidies for an International Oceanic Discovery Program (IODP) cruise. For this, satellite bathymetry data and seismic reflection profiles were used. These profiles were made available by the brazilian National Petroleum Agency (ANP). In the interpretation phase, the forms and patterns of reflectors termination were analyzed, in addition to its external and internal geometry. Preliminary results indicate that the intra-basal sedimentation of the Ceará Trough was strongly affected by the Plateau. PtC have apparently a significant accretion above its base. Correlating the morphology, past sedimentological data and seismic reflectors of the Plateau, it is possible to identify indications that it would be an isolated carbonate platform. Thus, the proposed model for PtC formation is that its substrate can be both a structural high or a volcanic building. At a certain moment, this foundation was in the photic or emergent zone, propitiating the reef development. This reef would have been drowned during the Miocene.