Details

Autor(en) / Beteiligte

• Souza, Juliana Maria Gonçalves
• Cubas, Nadaya
• Rabe, Claudio
• Letouzey, Jean
• Divies, Renaud
• Praeg, Daniel Brian
• Granjeon, Didier
• Cruz, Alberto Machado
• Silva, Cleverson Guizan
• dos Reis, Antonio Tadeu
• Gorini, Christian

Titel

Controls on overpressure evolution during the gravitational collapse of the Amazon deep-sea fan

Ist Teil von

• Marine and petroleum geology, 2020-11, Vol.121, p.104576, Article 104576

Ort / Verlag

Elsevier Ltd

Erscheinungsjahr

2020

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The Amazon Fan provides a natural laboratory to study the generation of overpressure, due to rapid late Cenozoic burial that has resulted in gravitational collapse above shale detachments. Here we examine collapse systems for the first time using the techniques of petroleum systems analysis. We propose an integrated methodology based on numerical modeling constrained by the structural restoration of a seismic profile across the southwestern fan. The results provide information on the evolution of pore pressure and temperature and their implications for the operation of the detachment and overlying extensional and compressional faults during the deposition of up to 6 km of sediment over the last 8 Ma. The modelled thermal history implies that fluid release by smectite-to-illite transformation has taken place within the thickening sedimentary succession, but has not significantly contributed to pore pressures along the detachment. Modeling of hydrocarbon generation and migration from source rocks beneath the fan indicates gas accumulated in successions at depths of 102–103 m beneath the detachment without influencing pore pressures along it. In contrast, model results indicate that overpressures have varied in response to disequilibrium compaction. Fault activity within the collapse system took place during phases of higher sedimentation rates, and ceased from 5.5 to 3.7 Ma when sediment supply to the SE fan decreased. From 2 Ma, renewed sediment flux and shelf-slope progradation led to a basinward migration both of overpressure along the detachment and of fault activity above it. We conclude that gravity tectonics in the Amazon Fan over the last 8 Ma have been mainly controlled by overpressures due to disequilibrium compaction, with secondary contributions from clay mineral transformation. Present-day pressure conditions show that the southeastern Amazon Fan is not at equilibrium and gravity driven deformation could occur at any time. •We study the evolution and generation of overpressure in the Amazon Fan and its related collapse.•Pore pressure evolution is investigated from structural restoration of a seismic profile followed by basin and mechanical modeling.•Overpressure is mainly due to disequilibrium compaction, with secondary contributions from clay-diagenesis and gas generation.•Massive sediment flux led to a downslope overpressure migration along the detachment, generating a migration of deformation.•Present-day pressure are not at equilibrium, and gravity driven deformation could occur at any time.