Fatores condicionantes do arcabouço estrutural da tectônica gravitacional do Cone do Amazonas

The Amazon Cone, part of the Amazon Mouth Basin, is intensely affected by gravity-driven tectonics. In this work, approximately 9000 km of multichannel seismic reflection lines were analysed, which enabled us to create a structural map, as well as a map of the the morphology of detachment surface and isopach of Neomiocen–Recen sedimentary covert. Three main structural domains were identified in the region: a proximal extensive domain, which extends since the edge of the shelf to the depth of 500 m, an intermediate domain that translate in a rigid way and a contractional domain which covers an area of approximately 1000 m to 1500 m in depth. The extensive domain is characterised as having synthetic listric faults and rollovers. On the other hand, the contractional domain is characterised as having thrust faults. The Amazon Cone thin-skinned extension system, whose detachment surface is located at the base of the Neomiocene sequence, is divided in two main compartments, which are: the South-eastern<br>Compartment and the North-western Compartment. The South-eastern Compartment is characterised as a narrow gravitational system (115 km wide), geographically limited to the continental slope and its extension can reach up to 1500 m in depth. However, the North-western Compartment is characterised as a wider gravitational system (152 km wide), which reaches up to 2500 m in depth. The morphology of the surface detachment (base of the shale layer under pressure) seems to represent an important role in the development of the structural framework of the area. Extensional faults are located in the region of higher gradient of the detachment surface, while the thrust faults are in the region of lower gradient. The mechanism of differential sedimentary overload is another important factor of development of the structural framework in the region, because the extensive structures are located in the thickest part of the depocentres and the thrust faults are located on the boarders of the depocentres.