Paleostress evolution of the Outer Kwanza basin (offshore Angola); comparison with the Congo basin and implications for the tectonic history of the Central segment of the West Africa passive margin

• Published in: Journal of African Earth Sciences
• Main Authors: Bah, Boubacar, Lacombe, Olivier, Beaudoin, Nicolas, Teboul, Pierre-Alexandre, Girard, Jean-Pierre, Gout, Claude
• Other Authors: Institut des Sciences de la Terre de Paris (iSTeP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Fluides Complexes et leurs Réservoirs (LFCR), TOTAL FINA ELF-Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Centre scientifique et Technique Jean Feger (CSTJF), TOTAL FINA ELF, Université de Pau et des Pays de l'Adour (UPPA), ANR-10-CAMP-0155,Réalisation d'études relatives à des équipements mutualisés,Réalisation d'études relatives à des équipements mutualisés au titre des actions du PIA(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2024
• Subjects: Paleostress reconstruction; Calcite twinning and stylolite roughness paleopiezometry ,Faults and fractures; Far-field lithospheric stress; U-Pb dating; Kwanza basin; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; South Atlantic Ocean
• Online Access: https://hal.science/hal-04673888; https://doi.org/10.1016/j.jafrearsci.2024.105382

International audience This study aims at reconstructing the paleostress history of the Outer (offshore) Kwanza basin (West African passive margin) and at comparing it to stress results acquired further north in the Congo basin. Three oriented borehole cores provided by TotalEnergies and reaching the syn-rift, Barremian-Aptian pre-salt carbonates offshore Angola were investigated. Paleopiezometry based on the Stylolite Roughness Inversion Technique (SRIT) and Calcite Twin Inversion Technique (CSIT) was combined with fracture analysis, U–Pb geochronology of carbonates and burial modelling to unravel the orientations and magnitudes of horizontal and vertical stresses affecting the pre-salt carbonates over time. Calcite twins were measured from a primary sparite matrix, and the inversion process unravelled a polyphase stress history, comprising ~ E-W and NE-SW extensional trends that we associate to the rifting (130-112 Ma) that led to the opening of the South Atlantic ocean. The ~ E-W extension is consistent with the early occurrence of N-S striking normal faults which developed in relation to the reactivation of inherited basement structures. This ~ E-W extension evolved during the Barremian-Aptian (?) into the dominant regional NE-SW extension marked by large-scale NW-SE striking normal faults. The stress history also comprises compressional and strike-slip stress regimes associated with a ~N-S trending σ1 which can be related to the transfer of orogenic stresses from the distant Africa-Eurasia plate boundary at ~67-60 Ma. Finally, compressional and strike-slip stress regimes associated with a ENE-WSW to ~E-W trending σ1 dominated since at least ~17-15 Ma (possibly ~34 Ma); they are interpreted as the expression of the mid-Atlantic ridge push. These (paleo)stress results are compared and combined with earlier paleostress reconstructions in the northern offshore Lower Congo basin (also belonging to the Central segment of the margin) and in the onshore Congo basin in order to refine the stress record and the ...