Estruturas rasas na margem equatorial ao largo do nordeste brasileiro (Estado do Ceará): análise de relevo e anomalias gravimétricas residuais

Abstract

The area of study is located in the atlantic equatorial margin shelf offshore Cear´ a State (Brazil), being originated during the formation of Equatorial Atlantic (Aptian). The residual gravity data highlight offshore continental framework structures, specially the Transbrasiliano Lineament and its offshore portion (Transversal Lineament). The continental margin basins (Cear´ a and offshore Potiguar) were also highlighted. The relief anomaly map shows that the superficial features are controlled by NE-SW precambrian structures, mainly in the segment offshore Acara´ u. In the outer shelf offshore Camocim, this control is due to both NW-SE and E-W features, probably related to transform tectonics in the Piau´ı-Camocim Sub-basin. E-W trends, possibly related to oceanic fractures, and NW-SE trends, probably related to precambrian structures, are characteristic of the central sector. The southeastern sector presents shelf sub parallel trends that approach contact between shallow basement and the offshore Potiguar basin. The neotectonic stress state is inferred as wrench-type with maximum horizontal stress sub parallel to the margin trend (mainly acting in the inner shelf) and extensional with minimum horizontal stress sub orthogonal to the margin trend (mainly in the outer shelf).