Dados da Submissão

Título

The remarkable symmetry between the Pelotas Basin and its African conjugated basins on the Namibian margin

Texto do resumo

The Pelotas Basin, located on the southern Brazilian margin, is associated with a deep tectonic trench generated in the rifting of the South Atlantic ocean and is clearly evidenced by its gravimetric response revealed by a prominent negative residual Bouguer anomaly. In this paper, attention is drawn to the outstanding symmetry observed between the ‘tectono-gravimetric trench’ of the Pelotas Basin and that of its conjugate basins on the continental margin of Namibia. Public domain bathymetric (GEBCO), satellite gravity (Topex-Poseidon) and magnetic (EMAG2) data were used in conjunction with 2D and 3D seismic data to produce a comprehensive re-interpretation of the main regional structures and crustal domains in the conjugate margins of Namibia and southern Brazil. As focus on the African margins of the south atlantic has intensified, Namibia’s offshore margins were recently studied with a focus on the Lüderitz and Orange basins using potential data integrated with 3D and 2D seismic. Following a defined data analysis methodology, important tectonic features resulting from reactivations on inherited continental structures were highlighted, structures which would have played an important role in controlling and supporting hydrocarbon accumulations. From this analysis, a more distal position of the continental-oceanic crust boundary (COB) was proposed, in addition to a regional trend of structural highs. These highs, generated by intense magmatic upwelling, are those that divided the basin into two symmetrical segments along its entire North-South extension. Within the magmatic trend of the Orange basin the structural high of the Kudu gas field stands out, a high resulting from a large magmatic dome injected into the crust from the depleted mantle. This dome, in turn, produces notable magnetic and gravimetric anomalies easily identified on potential data maps. A Cretaceous reconstruction of the southern margins of Africa and South America was produced from the analysis of tectonic structure continuity between the continents, as revealed in regional gravity and magnetics maps. The reconstruction produced by this methodology allows us to verify important structural relationships between the conjugated basins, as well as the tectonic reactivation of continental structures that evolved as oceanic fracture zones.

Palavras Chave

Bouguer gravity anomaly; Conjugate margins; Continent-Oceanic crustal boundary