Caracterização sísmica das falhas de transferência na Bacia de Campos

Abstract

The Campos Basin is a passive margin basin located at the southeastern Brazilian coast, limited by the Cabo Frio High to the south, and by the Vitoria High to the north. This basin evolved during the rifting process of the Gondwana supercontinent in the Late Jurassic / Early Cretaceous, which led to a final break-up by Late Aptian / Early Albian. The study of structural elements by regional seismic analysis is an efficient tool to understand tectonic dynamics. In this context, the characterization and analysis of transfer faults are extremely important to delineate the regional distribution of basindepocenters. Transfer faults are transtensive faults that transfer the displacement between two crustal sectors during different extensional strain. The objective of this study is to characterize these faults using potential methods such as gravimetric and magnetic surveys and a comprehensive seismic data analysis. In addition, STRM 90m satellite images were used in order to map a trend for transversal lineaments observed on the onshore basement. Transfer zones are mostly parallel to the main extensional vector on rift geometries. For the southeast coast of Brazil, the main structural axes strike EW and WNW-ESE, and these elements are trending subordinated to this direction [3]. Well log data was used to create synthetic seismograms and to establish a chronocorrelation with the main horizons. 2D seismic data was used to map the most important structures, such as, mini-basins, synthetic and antithetic faults, flower structures, grabens, horsts and halokinetic structures. The transfer faults were tentatively identified based on discontinuities observed from gravimetric data, linear magnetic anomalies with high amplitude and by flower structures, vertical to subvertical dips, inversion of throw and abrupt changes in the thickness of the layers observed from the 2D seismic data. It was possible to identify a group of eight main transverse faults in the Campos Basin, which segment the basement and the basin depocenters into different compartments and sectors. The structural domains are divided according to these sectors, and influence the salt behavior within the basin. Most of the faults were reactivated after the rift phase, affecting younger sedimentary layers. This work also compares the results obtained for the Campos Basin with relationships established in previous works in the Santos Basin, which focused on the rift structures and the transversal lineaments observed in the onshore segment of the continental margin. This relationship can also be observed in the Campos Basin, where the NW trend of onshore lineaments extends towards the offshore basin and advances towards the oceanic crust region